Introhydraulisduction Edited Version
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Transcript of Introhydraulisduction Edited Version
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
1 INTRODUCTION
11 HYDRAULICS
Man has been using fluids from ancient times to ease his problems of power and to obtain motion But the use of confined fluid is one of the modern developments in the field of fluid power
Fluid power system utilizes a confined fluid or pressurized fluid to transmit energy from a source to an area of use The system utilizes either a liquid or a gas medium for transmission of power The system utilizes either a liquid or gas medium for transmission of power The system utilizes either a liquid or a gas medium for transmission of power The system that utilizes pressurized liquid as working medium is known as hydraulic system For operation in machine tools usually oil is preferred as the working medium
The confined oil is the most versatile means of modifying motion and transmitting power It is as unyielding as steel and yet is infinitely flexible It can divide into any number of parts Each part can be utilized for doing work according to the mode required and can be reunited to work again as a whole
It can be used to obtain motion as well It can be moved rapidly in one part of its length and slowly in another No other means combine this degree of positiveness accuracy and flexibility The laws governing the liquids are simple than those governing electricity vapors and gases
The hydraulic systems have several advantages over the other methods of energy control ie mechanical or electrical
111 ADVANTAGES
1) High power to weight ratio 2) Fluid medium itself acts as a coolant and lubrication 3) Have linear torque speed characteristics 4) Safety and reliability of operation and ease of automation 5) Feasibility to obtain centralized control by suitable electrical interfacing 6) Simplicity of control of magnitude and direction of speed forces and feeds 7) Longer life of hydraulic elements even at higher speed and feed rates 8) Easy to obtain rapid change of linear and rotary motion9) Ease of prevention of overloading and resulting damage 10) Possibility of continuous supervision of pressure and forces acting on working
mechanisms
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
11) Convenient positioning of hydraulic devices in machines regardless of mechanical transmission
12) Possibility of operation with rigid dogs and limit switches13) Ability to build the system for a wide range of requirements
112 DISADVANTAGES
1 Leakage which decreases the efficiency of the system2 Variation in the temperature of oil affects the system3 Failure due to contamination of oil
The advantages in all aspects outweigh the disadvantages can be overcome by proper designing of elements The use of hydraulic and manrsquos physical and mental power enable a job to be done more quickly accurately and with lesser expenditure of energy
113 APPLICATIONS
The field of hydraulics has spread to every corner of application which ranges from
Simple ram drives in presses to flight control in air crafts and space ships As devices for tool slides and clamping mechanisms in machine tools For material handling conveying and steering mechanisms Marine and earth moving machinery Control of electrodes in nuclear reactors Drilling and driving mechanisms in mines
12 FINE BORING MACHINE
The fine boring machine used in HMT is a special purpose machine (SPM) used to in boring big and small end of a connecting rod The Fine Boring Machine is used in the process of enlarging a hole that has already been drilled (or cast) by means of a single-point cutting tool (or of a boring head containing several such tools) The Fine Boring Machine is used to achieve greater accuracy of the diameter of a hole and can be used to cut a tapered holeThere are various types of boring The boring bar may be supported on both ends (which only works if the existing hole is a through hole) or it may be supported at one end Line boring (line boring line-boring) implies the former Back boring (back boring back-boring) is the process of
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
reaching through an existing hole and then boring on the back side of the work piece (relative to the machine headstock)
The boring process can be executed on various machine tools including (1) general-purpose or universal machines such as lathes (turning centers) or milling machines (machining centers) and (2) machines designed to specialize in boring as a primary function such as jig borers and boring machines But finest accuracy of boring is obtained in a fine boring machine The boring process can be executed on various machine tools including (1) general-purpose or universal machines such as lathes (turning centers) or milling machines (machining centers) and (2) machines designed to specialize in boring as a primary function such as jig borers and boring machines To obtain complex Boring procedures a Fine Boring Machine
The dimensions between the piece and the tool bit can be changed about two axes to cut both vertically and horizontally into the internal surface The cutting tool is usually single point made of M2 and M3 high-speed
Steel or P10 and P01 carbide A tapered hole can also be made by swiveling the headBoring machines come in a large variety of sizes and styles Boring operations on small work pieces can be carried out on a lathe while larger work pieces are machined on boring mills Work pieces are commonly 1 to 4 meters (3 ft 3 in to 13 ft 1 in) in diameter but can be as large as 20 m (66 ft) Power requirements can be as much as 200 horsepower (150 kW) Cooling of the bores is done through a hollow passageway through the boring bar where coolant can flow freely Tungsten-alloy disks are sealed in the bar to counteract vibration and chatter during boring The control systems can be computer-based allowing for automation and increased consistency
Because boring is meant to decrease the product tolerances on pre-existing holes several design considerations must be madeFirst large length-to bore-diameters are not preferred due to cutting tool deflection
Next through holes are preferred over blind holes (holes that do not traverse the thickness of the work piece) Interrupted internal working surfaces where the cutting tool and surface have discontinuous contact should be avoided The boring bar is the protruding arm of the machine that holds cutting tool(s) and must be very rigid Various fixed cycles for boring are available in CNC controls For mills these are called using G-codes such asG76 G85 G86 G87 G88 G89 and other codes specific to particular control builders or machine tool builders
Although the Fine Boring Machine is efficient in accuracy it lags in some of the manual procedures of saddle movement and work clamping mechanism In order to overcome these disadvantages the following functions of the Fine boring Machine are considered for conversion from mechanical or manual operation to Hydraulic operation
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
I Saddle MovementII Work clamping
2 HYDRAULIC SYSTEM PARAMETERS AND ITS COMPONENTS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
21 PRINCIPLE AND PARAMETERS
The basic idea behind a hydraulic system is very simple Force that is applied at one point is transmitted to another point using an incompressible fluid The function of any hydraulic system can be divided into generation transmission utilization and control A hydraulic pump is used to obtain the necessary power and is the input component of the system Conversion of the hydraulic energy into useful mechanical energy is accomplished through actuators These are the output components of a hydraulic system
The modification of hydraulic energy is done in a controlled manner by adjusting and altering the various properties of oil
The main parameters of control are
1 Liquid pressure
2 Flow rate
3 Direction of flow
The liquid pressure creates force on a body that resists it This force is utilize to obtain motion ie useful work
The pressure exerted on confined oil can be transmitted and its transmission based on ldquoPASCALrsquos LAWrdquo which states that lsquopressure applied on a confined fluid is transited diminished in all directions and acts with equal force on equal areas right angle to itrdquo
Flow of this pressurized oil gives rise to the motion of actuators Force can be transmitted by the pressure but for motion to be obtained flow is essential The pump creates the flow and the volume of the oil passing at a given part in given time is called flow rate
The energy stored in oil is of two types
1 Kinetic energy by virtue velocity
2 Potential energy by virtue of pressure
In the transmission of energy there is conversion from one form to another According to law of conservation of energy energy can neither be created nor destroyed but can be converted from one form to another Based on this principle Bernoulli stated his principle which states ldquoIn a steady flow system the total energy at any point remains constantrdquo This principle is utilized in all hydraulic systems to obtain conversion of energy by controlling flow rate and pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
To obtain transfer of energy in a given direction direction control is essential This is affected by directing the pressurized oil in the required direction by using valves
Force and torque multiplication A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way independent of the distance between the input and output without the need for mechanical gears or levers either by altering the effective areas in two connected cylinders or the effective displacement (ccrev) between a pump and motor In normal cases hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and track drives for an excavator
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius and cylinder C2 is ten inches in radius If the force exerted on C1 is 10 lbf the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = 1049228rsup2) as C1 The downside to this is that you have to move C1 a hundred inches to move C2 one inch The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter
Pump and motor
If a hydraulic rotary pump with the displacement 10 ccrev is connected to a hydraulic rotary motor with 100 ccrev the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft but the shaft speed (revmin) for the motor is 10 times less than the pump shaft speed This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force defined as torque
Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic gear ratio
22 COMPONENTS OF HYDRAULIC SYSTEMS
The components of hydraulic system are
Hydraulic pump Control valves Actuators Reservoir
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
11) Convenient positioning of hydraulic devices in machines regardless of mechanical transmission
12) Possibility of operation with rigid dogs and limit switches13) Ability to build the system for a wide range of requirements
112 DISADVANTAGES
1 Leakage which decreases the efficiency of the system2 Variation in the temperature of oil affects the system3 Failure due to contamination of oil
The advantages in all aspects outweigh the disadvantages can be overcome by proper designing of elements The use of hydraulic and manrsquos physical and mental power enable a job to be done more quickly accurately and with lesser expenditure of energy
113 APPLICATIONS
The field of hydraulics has spread to every corner of application which ranges from
Simple ram drives in presses to flight control in air crafts and space ships As devices for tool slides and clamping mechanisms in machine tools For material handling conveying and steering mechanisms Marine and earth moving machinery Control of electrodes in nuclear reactors Drilling and driving mechanisms in mines
12 FINE BORING MACHINE
The fine boring machine used in HMT is a special purpose machine (SPM) used to in boring big and small end of a connecting rod The Fine Boring Machine is used in the process of enlarging a hole that has already been drilled (or cast) by means of a single-point cutting tool (or of a boring head containing several such tools) The Fine Boring Machine is used to achieve greater accuracy of the diameter of a hole and can be used to cut a tapered holeThere are various types of boring The boring bar may be supported on both ends (which only works if the existing hole is a through hole) or it may be supported at one end Line boring (line boring line-boring) implies the former Back boring (back boring back-boring) is the process of
Department of Mechanical engineering Dr Smce 2012 Page 2
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
reaching through an existing hole and then boring on the back side of the work piece (relative to the machine headstock)
The boring process can be executed on various machine tools including (1) general-purpose or universal machines such as lathes (turning centers) or milling machines (machining centers) and (2) machines designed to specialize in boring as a primary function such as jig borers and boring machines But finest accuracy of boring is obtained in a fine boring machine The boring process can be executed on various machine tools including (1) general-purpose or universal machines such as lathes (turning centers) or milling machines (machining centers) and (2) machines designed to specialize in boring as a primary function such as jig borers and boring machines To obtain complex Boring procedures a Fine Boring Machine
The dimensions between the piece and the tool bit can be changed about two axes to cut both vertically and horizontally into the internal surface The cutting tool is usually single point made of M2 and M3 high-speed
Steel or P10 and P01 carbide A tapered hole can also be made by swiveling the headBoring machines come in a large variety of sizes and styles Boring operations on small work pieces can be carried out on a lathe while larger work pieces are machined on boring mills Work pieces are commonly 1 to 4 meters (3 ft 3 in to 13 ft 1 in) in diameter but can be as large as 20 m (66 ft) Power requirements can be as much as 200 horsepower (150 kW) Cooling of the bores is done through a hollow passageway through the boring bar where coolant can flow freely Tungsten-alloy disks are sealed in the bar to counteract vibration and chatter during boring The control systems can be computer-based allowing for automation and increased consistency
Because boring is meant to decrease the product tolerances on pre-existing holes several design considerations must be madeFirst large length-to bore-diameters are not preferred due to cutting tool deflection
Next through holes are preferred over blind holes (holes that do not traverse the thickness of the work piece) Interrupted internal working surfaces where the cutting tool and surface have discontinuous contact should be avoided The boring bar is the protruding arm of the machine that holds cutting tool(s) and must be very rigid Various fixed cycles for boring are available in CNC controls For mills these are called using G-codes such asG76 G85 G86 G87 G88 G89 and other codes specific to particular control builders or machine tool builders
Although the Fine Boring Machine is efficient in accuracy it lags in some of the manual procedures of saddle movement and work clamping mechanism In order to overcome these disadvantages the following functions of the Fine boring Machine are considered for conversion from mechanical or manual operation to Hydraulic operation
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
I Saddle MovementII Work clamping
2 HYDRAULIC SYSTEM PARAMETERS AND ITS COMPONENTS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
21 PRINCIPLE AND PARAMETERS
The basic idea behind a hydraulic system is very simple Force that is applied at one point is transmitted to another point using an incompressible fluid The function of any hydraulic system can be divided into generation transmission utilization and control A hydraulic pump is used to obtain the necessary power and is the input component of the system Conversion of the hydraulic energy into useful mechanical energy is accomplished through actuators These are the output components of a hydraulic system
The modification of hydraulic energy is done in a controlled manner by adjusting and altering the various properties of oil
The main parameters of control are
1 Liquid pressure
2 Flow rate
3 Direction of flow
The liquid pressure creates force on a body that resists it This force is utilize to obtain motion ie useful work
The pressure exerted on confined oil can be transmitted and its transmission based on ldquoPASCALrsquos LAWrdquo which states that lsquopressure applied on a confined fluid is transited diminished in all directions and acts with equal force on equal areas right angle to itrdquo
Flow of this pressurized oil gives rise to the motion of actuators Force can be transmitted by the pressure but for motion to be obtained flow is essential The pump creates the flow and the volume of the oil passing at a given part in given time is called flow rate
The energy stored in oil is of two types
1 Kinetic energy by virtue velocity
2 Potential energy by virtue of pressure
In the transmission of energy there is conversion from one form to another According to law of conservation of energy energy can neither be created nor destroyed but can be converted from one form to another Based on this principle Bernoulli stated his principle which states ldquoIn a steady flow system the total energy at any point remains constantrdquo This principle is utilized in all hydraulic systems to obtain conversion of energy by controlling flow rate and pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
To obtain transfer of energy in a given direction direction control is essential This is affected by directing the pressurized oil in the required direction by using valves
Force and torque multiplication A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way independent of the distance between the input and output without the need for mechanical gears or levers either by altering the effective areas in two connected cylinders or the effective displacement (ccrev) between a pump and motor In normal cases hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and track drives for an excavator
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius and cylinder C2 is ten inches in radius If the force exerted on C1 is 10 lbf the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = 1049228rsup2) as C1 The downside to this is that you have to move C1 a hundred inches to move C2 one inch The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter
Pump and motor
If a hydraulic rotary pump with the displacement 10 ccrev is connected to a hydraulic rotary motor with 100 ccrev the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft but the shaft speed (revmin) for the motor is 10 times less than the pump shaft speed This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force defined as torque
Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic gear ratio
22 COMPONENTS OF HYDRAULIC SYSTEMS
The components of hydraulic system are
Hydraulic pump Control valves Actuators Reservoir
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
reaching through an existing hole and then boring on the back side of the work piece (relative to the machine headstock)
The boring process can be executed on various machine tools including (1) general-purpose or universal machines such as lathes (turning centers) or milling machines (machining centers) and (2) machines designed to specialize in boring as a primary function such as jig borers and boring machines But finest accuracy of boring is obtained in a fine boring machine The boring process can be executed on various machine tools including (1) general-purpose or universal machines such as lathes (turning centers) or milling machines (machining centers) and (2) machines designed to specialize in boring as a primary function such as jig borers and boring machines To obtain complex Boring procedures a Fine Boring Machine
The dimensions between the piece and the tool bit can be changed about two axes to cut both vertically and horizontally into the internal surface The cutting tool is usually single point made of M2 and M3 high-speed
Steel or P10 and P01 carbide A tapered hole can also be made by swiveling the headBoring machines come in a large variety of sizes and styles Boring operations on small work pieces can be carried out on a lathe while larger work pieces are machined on boring mills Work pieces are commonly 1 to 4 meters (3 ft 3 in to 13 ft 1 in) in diameter but can be as large as 20 m (66 ft) Power requirements can be as much as 200 horsepower (150 kW) Cooling of the bores is done through a hollow passageway through the boring bar where coolant can flow freely Tungsten-alloy disks are sealed in the bar to counteract vibration and chatter during boring The control systems can be computer-based allowing for automation and increased consistency
Because boring is meant to decrease the product tolerances on pre-existing holes several design considerations must be madeFirst large length-to bore-diameters are not preferred due to cutting tool deflection
Next through holes are preferred over blind holes (holes that do not traverse the thickness of the work piece) Interrupted internal working surfaces where the cutting tool and surface have discontinuous contact should be avoided The boring bar is the protruding arm of the machine that holds cutting tool(s) and must be very rigid Various fixed cycles for boring are available in CNC controls For mills these are called using G-codes such asG76 G85 G86 G87 G88 G89 and other codes specific to particular control builders or machine tool builders
Although the Fine Boring Machine is efficient in accuracy it lags in some of the manual procedures of saddle movement and work clamping mechanism In order to overcome these disadvantages the following functions of the Fine boring Machine are considered for conversion from mechanical or manual operation to Hydraulic operation
Department of Mechanical engineering Dr Smce 2012 Page 3
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
I Saddle MovementII Work clamping
2 HYDRAULIC SYSTEM PARAMETERS AND ITS COMPONENTS
Department of Mechanical engineering Dr Smce 2012 Page 4
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
21 PRINCIPLE AND PARAMETERS
The basic idea behind a hydraulic system is very simple Force that is applied at one point is transmitted to another point using an incompressible fluid The function of any hydraulic system can be divided into generation transmission utilization and control A hydraulic pump is used to obtain the necessary power and is the input component of the system Conversion of the hydraulic energy into useful mechanical energy is accomplished through actuators These are the output components of a hydraulic system
The modification of hydraulic energy is done in a controlled manner by adjusting and altering the various properties of oil
The main parameters of control are
1 Liquid pressure
2 Flow rate
3 Direction of flow
The liquid pressure creates force on a body that resists it This force is utilize to obtain motion ie useful work
The pressure exerted on confined oil can be transmitted and its transmission based on ldquoPASCALrsquos LAWrdquo which states that lsquopressure applied on a confined fluid is transited diminished in all directions and acts with equal force on equal areas right angle to itrdquo
Flow of this pressurized oil gives rise to the motion of actuators Force can be transmitted by the pressure but for motion to be obtained flow is essential The pump creates the flow and the volume of the oil passing at a given part in given time is called flow rate
The energy stored in oil is of two types
1 Kinetic energy by virtue velocity
2 Potential energy by virtue of pressure
In the transmission of energy there is conversion from one form to another According to law of conservation of energy energy can neither be created nor destroyed but can be converted from one form to another Based on this principle Bernoulli stated his principle which states ldquoIn a steady flow system the total energy at any point remains constantrdquo This principle is utilized in all hydraulic systems to obtain conversion of energy by controlling flow rate and pressure
Department of Mechanical engineering Dr Smce 2012 Page 5
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
To obtain transfer of energy in a given direction direction control is essential This is affected by directing the pressurized oil in the required direction by using valves
Force and torque multiplication A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way independent of the distance between the input and output without the need for mechanical gears or levers either by altering the effective areas in two connected cylinders or the effective displacement (ccrev) between a pump and motor In normal cases hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and track drives for an excavator
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius and cylinder C2 is ten inches in radius If the force exerted on C1 is 10 lbf the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = 1049228rsup2) as C1 The downside to this is that you have to move C1 a hundred inches to move C2 one inch The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter
Pump and motor
If a hydraulic rotary pump with the displacement 10 ccrev is connected to a hydraulic rotary motor with 100 ccrev the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft but the shaft speed (revmin) for the motor is 10 times less than the pump shaft speed This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force defined as torque
Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic gear ratio
22 COMPONENTS OF HYDRAULIC SYSTEMS
The components of hydraulic system are
Hydraulic pump Control valves Actuators Reservoir
Department of Mechanical engineering Dr Smce 2012 Page 6
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
I Saddle MovementII Work clamping
2 HYDRAULIC SYSTEM PARAMETERS AND ITS COMPONENTS
Department of Mechanical engineering Dr Smce 2012 Page 4
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
21 PRINCIPLE AND PARAMETERS
The basic idea behind a hydraulic system is very simple Force that is applied at one point is transmitted to another point using an incompressible fluid The function of any hydraulic system can be divided into generation transmission utilization and control A hydraulic pump is used to obtain the necessary power and is the input component of the system Conversion of the hydraulic energy into useful mechanical energy is accomplished through actuators These are the output components of a hydraulic system
The modification of hydraulic energy is done in a controlled manner by adjusting and altering the various properties of oil
The main parameters of control are
1 Liquid pressure
2 Flow rate
3 Direction of flow
The liquid pressure creates force on a body that resists it This force is utilize to obtain motion ie useful work
The pressure exerted on confined oil can be transmitted and its transmission based on ldquoPASCALrsquos LAWrdquo which states that lsquopressure applied on a confined fluid is transited diminished in all directions and acts with equal force on equal areas right angle to itrdquo
Flow of this pressurized oil gives rise to the motion of actuators Force can be transmitted by the pressure but for motion to be obtained flow is essential The pump creates the flow and the volume of the oil passing at a given part in given time is called flow rate
The energy stored in oil is of two types
1 Kinetic energy by virtue velocity
2 Potential energy by virtue of pressure
In the transmission of energy there is conversion from one form to another According to law of conservation of energy energy can neither be created nor destroyed but can be converted from one form to another Based on this principle Bernoulli stated his principle which states ldquoIn a steady flow system the total energy at any point remains constantrdquo This principle is utilized in all hydraulic systems to obtain conversion of energy by controlling flow rate and pressure
Department of Mechanical engineering Dr Smce 2012 Page 5
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
To obtain transfer of energy in a given direction direction control is essential This is affected by directing the pressurized oil in the required direction by using valves
Force and torque multiplication A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way independent of the distance between the input and output without the need for mechanical gears or levers either by altering the effective areas in two connected cylinders or the effective displacement (ccrev) between a pump and motor In normal cases hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and track drives for an excavator
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius and cylinder C2 is ten inches in radius If the force exerted on C1 is 10 lbf the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = 1049228rsup2) as C1 The downside to this is that you have to move C1 a hundred inches to move C2 one inch The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter
Pump and motor
If a hydraulic rotary pump with the displacement 10 ccrev is connected to a hydraulic rotary motor with 100 ccrev the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft but the shaft speed (revmin) for the motor is 10 times less than the pump shaft speed This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force defined as torque
Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic gear ratio
22 COMPONENTS OF HYDRAULIC SYSTEMS
The components of hydraulic system are
Hydraulic pump Control valves Actuators Reservoir
Department of Mechanical engineering Dr Smce 2012 Page 6
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
Department of Mechanical engineering Dr Smce 2012 Page 7
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
Department of Mechanical engineering Dr Smce 2012 Page 8
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
Department of Mechanical engineering Dr Smce 2012 Page 9
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
Department of Mechanical engineering Dr Smce 2012 Page 10
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
21 PRINCIPLE AND PARAMETERS
The basic idea behind a hydraulic system is very simple Force that is applied at one point is transmitted to another point using an incompressible fluid The function of any hydraulic system can be divided into generation transmission utilization and control A hydraulic pump is used to obtain the necessary power and is the input component of the system Conversion of the hydraulic energy into useful mechanical energy is accomplished through actuators These are the output components of a hydraulic system
The modification of hydraulic energy is done in a controlled manner by adjusting and altering the various properties of oil
The main parameters of control are
1 Liquid pressure
2 Flow rate
3 Direction of flow
The liquid pressure creates force on a body that resists it This force is utilize to obtain motion ie useful work
The pressure exerted on confined oil can be transmitted and its transmission based on ldquoPASCALrsquos LAWrdquo which states that lsquopressure applied on a confined fluid is transited diminished in all directions and acts with equal force on equal areas right angle to itrdquo
Flow of this pressurized oil gives rise to the motion of actuators Force can be transmitted by the pressure but for motion to be obtained flow is essential The pump creates the flow and the volume of the oil passing at a given part in given time is called flow rate
The energy stored in oil is of two types
1 Kinetic energy by virtue velocity
2 Potential energy by virtue of pressure
In the transmission of energy there is conversion from one form to another According to law of conservation of energy energy can neither be created nor destroyed but can be converted from one form to another Based on this principle Bernoulli stated his principle which states ldquoIn a steady flow system the total energy at any point remains constantrdquo This principle is utilized in all hydraulic systems to obtain conversion of energy by controlling flow rate and pressure
Department of Mechanical engineering Dr Smce 2012 Page 5
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
To obtain transfer of energy in a given direction direction control is essential This is affected by directing the pressurized oil in the required direction by using valves
Force and torque multiplication A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way independent of the distance between the input and output without the need for mechanical gears or levers either by altering the effective areas in two connected cylinders or the effective displacement (ccrev) between a pump and motor In normal cases hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and track drives for an excavator
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius and cylinder C2 is ten inches in radius If the force exerted on C1 is 10 lbf the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = 1049228rsup2) as C1 The downside to this is that you have to move C1 a hundred inches to move C2 one inch The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter
Pump and motor
If a hydraulic rotary pump with the displacement 10 ccrev is connected to a hydraulic rotary motor with 100 ccrev the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft but the shaft speed (revmin) for the motor is 10 times less than the pump shaft speed This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force defined as torque
Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic gear ratio
22 COMPONENTS OF HYDRAULIC SYSTEMS
The components of hydraulic system are
Hydraulic pump Control valves Actuators Reservoir
Department of Mechanical engineering Dr Smce 2012 Page 6
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
Department of Mechanical engineering Dr Smce 2012 Page 7
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
Department of Mechanical engineering Dr Smce 2012 Page 8
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
Department of Mechanical engineering Dr Smce 2012 Page 9
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
Department of Mechanical engineering Dr Smce 2012 Page 10
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
Department of Mechanical engineering Dr Smce 2012 Page 11
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
Department of Mechanical engineering Dr Smce 2012 Page 12
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
Department of Mechanical engineering Dr Smce 2012 Page 13
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
Department of Mechanical engineering Dr Smce 2012 Page 14
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
Department of Mechanical engineering Dr Smce 2012 Page 15
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
To obtain transfer of energy in a given direction direction control is essential This is affected by directing the pressurized oil in the required direction by using valves
Force and torque multiplication A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way independent of the distance between the input and output without the need for mechanical gears or levers either by altering the effective areas in two connected cylinders or the effective displacement (ccrev) between a pump and motor In normal cases hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and track drives for an excavator
Examples
Two hydraulic cylinders interconnected
Cylinder C1 is one inch in radius and cylinder C2 is ten inches in radius If the force exerted on C1 is 10 lbf the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = 1049228rsup2) as C1 The downside to this is that you have to move C1 a hundred inches to move C2 one inch The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter
Pump and motor
If a hydraulic rotary pump with the displacement 10 ccrev is connected to a hydraulic rotary motor with 100 ccrev the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft but the shaft speed (revmin) for the motor is 10 times less than the pump shaft speed This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force defined as torque
Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic gear ratio
22 COMPONENTS OF HYDRAULIC SYSTEMS
The components of hydraulic system are
Hydraulic pump Control valves Actuators Reservoir
Department of Mechanical engineering Dr Smce 2012 Page 6
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
Department of Mechanical engineering Dr Smce 2012 Page 8
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
Department of Mechanical engineering Dr Smce 2012 Page 9
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Accumulators Hydraulic fluid Filters Tubes pipes and hoses Seals fittings and connections
221 HYDRAULIC PUMP
Hydraulic pumps supply fluid to the components in the system Pressure in the system develops in reaction to the load Hence a pump rated for 5000 psi is capable of maintaining flow against a load of 5000
psi Pumps have a power density about ten times greater than an electric motor (by volume) They are powered by an electric motor or an engine connected through gears belts or a
flexible elastomeric coupling to reduce vibration
Common types of hydraulic pumps to hydraulic machinery applications are
Gear pump cheap durable (especially in g-rotor form) simple Less efficient because they are constant (fixed) displacement and mainly suitable for pressures below 20 MPa (3000 psi)
Vane pump cheap and simple reliable Good for higher-flow low-pressure output Axial piston pump many designed with a variable displacement mechanism to vary
output flow for automatic control of pressure There are various axial piston pump designs including swash plate (sometimes referred to as a valve plate pump) and check ball (sometimes referred to as a wobble plate pump)
The most common is the swash plate pump A variable-angle swash plate causes the pistons to reciprocate a greater or lesser distance per rotation allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate lower pressure and vice versa)
Radial piston pumps is a pump that is normally used for very high pressure at small flows
Piston pumps are more expensive than gear or vane pumps but provide longer life operating at higher pressure with difficult fluids and longer continuous duty cycles Piston pumps make up one half of a hydrostatic transmission
TYPES OF HYDRAULIC PUMPS
Gear pumps Rotary vane pumps
Department of Mechanical engineering Dr Smce 2012 Page 7
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
Department of Mechanical engineering Dr Smce 2012 Page 8
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
Department of Mechanical engineering Dr Smce 2012 Page 9
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
Department of Mechanical engineering Dr Smce 2012 Page 10
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Screw pumps Bent axis pumps Axial piston pumps swash plate principle Radial piston pumps Peristaltic pumps
2211 GEAR PUMPS
Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps The swept volume or displacement of gear pumps for hydraulics will be between about 1
cm3 (0001 litre) and 200 cm3 (02 litre) They have the lowest volumetric efficiency (nv = 90 ) of all three basic pump types
(gear vane and piston pumps) [1] These pumps create pressure through the meshing of the gear teeth which forces fluid around the gears to pressurize the outlet side
For lubrication the gear pump uses a small amount of oil from the pressurized side of the gears bleeds this through the (typically) hydrodynamic bearings and vents the same oil either to the low pressure side of the gears or through a dedicated drain port on the pump housing
Some gear pumps can be quite noisy compared to other types but modern gear pumps are highly reliable and much quieter than older models
This is in part due to designs incorporating split gears helical gear teeth and higher precisionquality tooth profiles that mesh and unmesh more smoothly reducing pressure ripple and related detrimental problems
Another positive attribute of the gear pump is that catastrophic breakdown is a lot less common than in most other types of hydraulic pumps
This is because the gears gradually wear down the housing andor main bushings reducing the volumetric efficiency of the pump gradually until it is all but useless
This often happens long before wear causes the unit to seize or break down
2212 ROTARY VANE PUMPS
Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps but are also used for mid pressures up to 180 bars in general
Modern units can exceed 300 bars in continuous operation although vane pumps are not regarded as high pressure components Some types of vane pumps can change the center of the vane body so that a simple adjustable pump is obtained
Department of Mechanical engineering Dr Smce 2012 Page 8
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
Department of Mechanical engineering Dr Smce 2012 Page 9
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
These adjustable vane pumps are in general constant pressure or constant power pumps the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until equilibrium is reached
A critical element in vane pump design is how the vanes are pushed into contact with the pump housing and how the vane tips are machined at this very point
Several types of lip designs are used and the main objective is to provide a tight seal between the inside of the housing and the vane and at the same time to minimize wear and metal-to-metal contact
Forcing the vane out of the rotating center and towards the pump housing is accomplished using spring-loaded vanes or more traditionally vanes loaded hydro dynamically (via the pressurized system fluid)
2213 SCREW PUMPS
Screw pumps (fixed displacement) are a double Archimedes screw but closed This means that two screws are used in one body The pumps are used for high flows and relatively low pressure (max 100 bar)
They were used on board ships where the constant pressure hydraulic system was going through the whole ship especially for the control of ball valves but also for the steering gear and help drive systems
The advantage of the screw pumps is the low sound level of these pumps the efficiency is not that high
The major problem of screw pumps is the hydraulic reaction forces which is transmitted axially opposed to the flow direction there are two ways to overcome this problem1- put a thrust bearing beneath each rotor2- make a hydraulic balance with directing a hydraulic force to a piston under the rotor
Types of screw pumps
1- Single end2- Double end3- Single rotor4- Multi rotor timed5- Multi rotor untimed
2214 BENT AXIS PUMPS
Bent axis pumps axial piston pumps and motors using the bent axis principle fixed or adjustable displacement exists in two different basic designs
Department of Mechanical engineering Dr Smce 2012 Page 9
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The Thoma-principle (engineer Hans Thoma Germany patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark patent 1960) with spherical-shaped pistons in one piece with the piston rod piston rings and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co)
These have the best efficiency of all pumps Although in general the largest displacements are approximately one litre per revolution
if necessary a two-liter swept volume pump can be built Often variable-displacement pumps are used so that the oil flow can be adjusted
carefully These pumps can in general work with a working pressure of up to 350ndash420 bars in
continuous work
2215 AXIAL PISTON PUMPS SWASHPLATE PRINCIPLE
Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model
They have the advantage of being more compact in design The pumps are easier and more economical to manufacture the disadvantage is that they
are more sensitive to oil contamination
2216 RADIAL PISTON PUMPS
Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows
Pressures of up to 650 bar are normal In fact variable displacement is not possible but sometimes the pump is designed in such
a way that the plungers can be switched off one by one so that a sort of variable displacement pump is obtained
2217 PERISTALTIC PUMPS
Peristaltic pumps are not generally used for high pressures
222 CONTROL VALVES
Department of Mechanical engineering Dr Smce 2012 Page 10
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
Department of Mechanical engineering Dr Smce 2012 Page 11
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
Department of Mechanical engineering Dr Smce 2012 Page 12
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Directional control valves route the fluid to the desired actuator They usually consist of a spool inside a cast iron or steel housing The spool slides to different positions in the housing intersecting grooves and channels
route the fluid based on the spools position The spool has a central (neutral) position maintained with springs in this position the
supply fluid is blocked or returned to tank Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a
return path from the actuator to tank When the spool is moved to the opposite direction the supply and return paths are
switched When the spool is allowed to return to neutral (center) position the actuator fluid paths
are blocked locking it in position Directional control valves are usually designed to be stackable with one valve for each
hydraulic cylinder and one fluid input supplying all the valves in the stack Tolerances are very tight in order to handle the high pressure and avoid leaking spools
typically have a clearance with the housing of less than a thousandth of an inch (25 μm) The valve block will be mounted to the machines frame with a three point pattern to
avoid distorting the valve block and jamming the valves sensitive components The spool position may be actuated by mechanical levers hydraulic pilot pressure or
solenoids which push the spool left or right A seal allows part of the spool to protrude outside the housing where it is accessible to
the actuator The main valve block is usually a stack of off the shelf directional control valves chosen
by flow capacity and performance Some valves are designed to be proportional (flow rate proportional to valve position)
while others may be simply on-off The control valve is one of the most expensive and sensitive parts of a hydraulic circuit
1 Pressure relief valves are used in several places in hydraulic machinery on the return circuit to maintain a small amount of pressure for brakes pilot lines etc On hydraulic cylinders to prevent overloading and hydraulic lineseal rupture On the hydraulic reservoir to maintain a small positive pressure this excludes moisture and contamination
2 Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits
3 Sequence valves control the sequence of hydraulic circuits to ensure that one hydraulic cylinder is fully extended before another starts its stroke for example
4 Shuttle valves provide a logical or function 5 Check valves are one-way valves allowing an accumulator to charge and
maintain its pressure after the machine is turned off for example
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
6 Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal For instance if the load should not be held by the check valve anymore Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder
7 Counterbalance valves are in fact a special type of pilot controlled check valve Whereas the check valve is open or closed the counterbalance valve acts a bit like a pilot controlled flow control
8 Cartridge valves are in fact the inner part of a check valve they are off the shelf components with a standardized envelope making them easy to populate a proprietary valve block They are available in many configurations onoff proportional pressure relief etc They generally screw into a valve block and are electrically controlled to provide logic and automated functions
9 Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low or safely vent fluid if pressure becomes too high
10 Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator such as accumulator charging cooling fan operation air conditioning power etc They are usually custom valves designed for the particular machine and may consist of a metal block with ports and channels drilled Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed
223 ACTUATORS
Hydraulic cylinder Swash plates are used in hydraulic motors requiring highly accurate control and also in
no stop continuous (360deg) precision positioning mechanisms These are frequently driven by several hydraulic pistons acting in sequence
Hydraulic motor (a pump plumbed in reverse) Hydrostatic transmission brakes
2231 HYDRAULIC CYLINDER
(Also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke
It has many applications notably in engineering vehicles Hydraulic cylinders get their power from pressurized hydraulic fluid which is typically oil
The hydraulic cylinder consists of a cylinder barrel in which a piston connected to a piston rod moves back and forth
Department of Mechanical engineering Dr Smce 2012 Page 12
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
Department of Mechanical engineering Dr Smce 2012 Page 13
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
Department of Mechanical engineering Dr Smce 2012 Page 14
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
Department of Mechanical engineering Dr Smce 2012 Page 15
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The barrel is closed on each end by the cylinder bottom (also called the cap end) and by the cylinder head where the piston rod comes out of the cylinder The piston has sliding rings and seals
The piston divides the inside of the cylinder in two chambers the bottom chamber (cap end) and the piston rod side chamber (rod end)
The hydraulic pressure acts on the piston to do linear work and motion Flanges trunnions andor clevisses are mounted to the cylinder body The piston rod also has mounting attachments to connect the cylinder to the object or
machine component that it is pushing A hydraulic cylinder is the actuator or motor side of this system The generator side of the hydraulic system is the hydraulic pump which brings in a
fixed or regulated flow of oil to the bottom side of the hydraulic cylinder to move the piston rod upwards
The piston pushes the oil in the other chamber back to the reservoir If we assume that the oil pressure in the piston rod chamber is approximately zero the
force F on the piston rod equals the pressure in the cylinder times the piston area A
F = PA
2232 SWASHPLATE
A swashplate consists of a disk attached to a shaft If the disk is aligned squarely on the shaft then rotation of the shaft will turn the disk with it and no swashplate effect will be seen
Even a slight displacement of the disk from the square position however will cause the disk edge to appear to describe an oscillating linear path when viewed from a non-rotating point of view away from the shaft
The greater the angle of the plate to the shaft the more exaggerated the apparent linear motion will be
The apparent linear motion can be turned into an actual linear motion by having a follower stationary with respect to the shaft but which presses against the top or bottom edge of the plate
The device has many similarities to the cam The swashplate engine uses a swashplate in place of a crankshaft to translate the motion
of a piston into rotary motion Internal combustion engines and Sterling engines have been built using this mechanism The axial piston pump drives a series of pistons aligned coaxially with a shaft through a
swashplate to pump a fluid
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A helicopter swashplate is a pair of plates one rotating and one fixed that are centered on the main rotor shaft
The rotating plate is linked to the rotor head and the fixed plate is linked to the operator controls
Displacement of the alignment of the fixed plate is transferred to the rotating plate where it becomes reciprocal motion of the rotor blade linkages
This type of pitch control known as cyclic pitch allows the helicopter rotor to provide selective lift in any direction
Notating flow meters and pumps have similar motions to the wobble of a swashplate but do not necessarily transform the motion to a reciprocating motion at any time
Active Electronically Scanned Array (AESA) radars are flat plates that can scan up to sixty degrees in any direction from directly ahead of them
By mounting an AESA radar on a swashplate the swashplate angle is added to the electronic scan angle
The typical swashplate angle chosen for this application is 40 degrees so the radar can scan a total angle of 200 degrees out of 360
2233 HYDRAULIC MOTORS
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation)
The hydraulic motor is the rotary counterpart of the hydraulic cylinder Conceptually a hydraulic motor should be interchangeable with a hydraulic pump
because it performs the opposite function - much as the conceptual DC electric motor is interchangeable with a DC electrical generator
However most hydraulic pumps cannot be used as hydraulic motors because they cannot be back driven
Also a hydraulic motor is usually designed for the working pressure at both sides of the motor
Hydraulic pumps motors and cylinders can be combined into hydraulic drive systems One or more hydraulic pumps coupled to one or more hydraulic motors constitutes a
hydraulic transmission Hydraulic motor types
1) Gear and vane motors2) Axial plunger motors3) Radial piston motors
224 HYDRAULIC FLUID
Also known as tractor fluid hydraulic fluid is the life of the hydraulic circuit
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
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Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is usually petroleum oil with various additives Some hydraulic machines require fire resistant fluids depending on their applications In some factories where food is prepared either an edible oil or water is used as a
working fluid for health and safety reasons In addition to transferring energy hydraulic fluid needs to lubricate components suspend
contaminants and metal filings for transport to the filter and to function well to several hundred degrees Fahrenheit or Celsius
225 FILTERS
Filters are an important part of hydraulic systems Metal particles are continually produced by mechanical components and need to be removed along with other contaminants
Filters may be positioned in many locations The filter may be located between the reservoir and the pump intake
Blockage of the filter will cause cavitation and possibly failure of the pump Sometimes the filter is located between the pump and the control valves
This arrangement is more expensive since the filter housing is pressurized but eliminates cavitation problems and protects the control valve from pump failures
The third common filter location is just before the return line enters the reservoir This location is relatively insensitive to blockage and does not require a pressurized
housing but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once
226 TUBES PIPES AND HOSES
Hydraulic tubes are seamless steel precision pipes specially manufactured for hydraulics The tubes have standard sizes for different pressure ranges with standard diameters up to
100 mm The tubes are supplied by manufacturers in lengths of 6 m cleaned oiled and plugged The tubes are interconnected by different types of flanges (especially for the larger sizes
and pressures) welding conesnipples (with o-ring seal) several types of flare connection and by cut-rings
In larger sizes hydraulic pipes are used Direct joining of tubes by welding is not acceptable since the interior cannot be
inspected Hydraulic pipe is used in case standard hydraulic tubes are not available Generally these
are used for low pressure
Department of Mechanical engineering Dr Smce 2012 Page 15
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
Department of Mechanical engineering Dr Smce 2012 Page 16
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
Department of Mechanical engineering Dr Smce 2012 Page 18
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
They can be connected by threaded connections but usually by welds Because of the larger diameters the pipe can usually be inspected internally after welding
Black pipe is non-galvanized and suitable for welding Hydraulic hose is graded by pressure temperature and fluid compatibility Hoses are used when pipes or tubes cannot be used usually to provide flexibility for
machine operation or maintenance The hose is built up with rubber and steel layers A rubber interior is surrounded by multiple layers of woven wire and rubber The
exterior is designed for abrasion resistance The bend radius of hydraulic hose is carefully designed into the machine since hose
failures can be deadly and violating the hoses minimum bend radius will cause failure Hydraulic hoses generally have steel fittings swaged on the ends The weakest part of the
high pressure hose is the connection of thehose to the fitting Another disadvantage of hoses is the shorter life of rubber which requires periodic replacementusually at five to seven year intervals
Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned
Usually steel piping is painted outside Where flare and other couplings are used the paint is removed under the nut and is a
location where corrosion can begin For this reason in marine applications most piping is stainless steel
227 SEALS FITTINGS AND CONNECTIONS
In general valves cylinders and pumps have female threaded bosses for the fluid connection and hoses have female ends with captive nuts
A male-male fitting is chosen to connect the two Many standardized systems are in use
3 HYDRAULIC FLUIDS
Department of Mechanical engineering Dr Smce 2012 Page 16
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
Department of Mechanical engineering Dr Smce 2012 Page 18
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Hydraulic fluid is the chief element of a hydraulic power system The functions and different
motions are obtained by suitably altering the working conditions of this fluid Though fluid
generally means a liquid or a gas in power hydraulics it means specially compounded petroleum
oil The selection and handling of the hydraulic oil in the system has an important bearing on its
performance and on the life of hydraulic component
31 FUNCTIONS OF FLUID IN HYDRAULIC SYSTEM
The hydraulic fluid has four primary functions
1 To transmit power2 To lubricate the moving parts3 To seal the clearance between the moving parts4 To take away the heat from the components and dissipating it thus cooling the
component
In addition to the above functions it has to fulfill the following quality requirements
1 It must prevent rust2 Prevent formation of sludge gum and varnish3 Depress foaming4 Maintain viscosity over a wide range of temperature5 Prevent corrosion and pitting6 Should have compatibility with seals and gaskets
These quality requirements are obtained by mixing the oil with various additives
32 TYPES OF FLUIDS
1 Petroleum oils These are the most widely used base for hydraulic oils The characteristics of the oil depend upon the type of the crude oil the degree of refining and
Department of Mechanical engineering Dr Smce 2012 Page 17
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
Department of Mechanical engineering Dr Smce 2012 Page 18
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
the additives used These oils have excellent lubricating anti-wear properties and are stable for over a wide range of temperatures Oil naturally protects against rust seals well dissipates heat easily and is easy to keep clean by filtration and gravity separation of containments
2 Fire resistance oils The disadvantages of petroleum oils are that they are combustible and are able to develop fire accidents when used for operation like heat treating welding die casting etc hence fire resistance oils required The major type of oils are
a)Water glycols These are oils compounded of 35 to 40 of water to provide for fire resistance glycol and a water soluble thickener to improve viscosity These oils have good wear resistance and lubricity provided that high speeds and loads are avoided
b) Water oil emulsion These oils are the least expensive fire resistance oils These are compounded of water and oil with emulsifier stabilizers and other additives The operating temperature must be kept low with these oils to avoid evaporation and oxidation These oils have a great affinity for contaminants and require extra attention to filtration These oils are generally compatible with all metals and seals
33 FLUID MAINTAINANCE
Hydraulic oil is an expensive item Further changing the oil and flushing or cleaning improperly maintained systems is time consuming and costly Hence proper care is extremely essential Contamination of the oil must be prevented both during the operation and maintenance The important points to be noted are
1 The oil must be clean and free from moisture to avoid damage to close fitting parts2 During transfer and changing oil clean container and hoses should be used3 During operation the system must be air tight4 The reservoir must be kept clean and periodically washed proper level by oil must be
maintained to ensure circulation air separation and heat dissipation
34 RESERVIOR
Department of Mechanical engineering Dr Smce 2012 Page 18
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The hydraulic oil should be stored in a storage tank or a reservoir Care must be taken such that the oil should be clean and kept at Proper operating temperature
The oil reservoirs used in hydraulic systems are expected to carry out the following functions
1 It should act as a storage space for the oil before pumping into the circuit2 It should be able to dissipate the heat generated and maintain proper uniform operating
temperature3 It should provide for a separation of air and allow for settle of contaminants
35 CONSTRUCTION
A typical reservoir is shown in fig 31 the tank is constructed of welded steel plates with extension of end plates supporting the unit on the floor The entire inside of the tank is painted with a sealer to reduce rust The bottom of the tank is dished and has a drain plug at the lowest point of flushing Easy removable covers are adopted for easy cleaning and an oil level indicator is provided for checking the oil level Breather filler with a strainer is used at the top of the tank to fill oil A baffle plate is provided at the middle of the tank so that it separates the suction side from the delivery side The baffle plate also helps in
1 Preventing turbulence inside the tank2 Allowing contaminants to settle down3 Allowing entrapped air to escape4 Giving more time for oil to dissipate heat
36 RESERVIOR SIZING
A large tank is always desirable to promote cooling and separation of contaminants The tank must store all the oil in the system so that a high level is maintained enough to prevent whirlpool effect at the pump suction As a general rule reservoir is designed to hold at least four times the quantity of the oil circulated by the pump
Specification for hydraulic oil is given in the table
Department of Mechanical engineering Dr Smce 2012 Page 19
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4 HYDRAULIC ELEMENTS
A hydraulic system consists of various devices and instruments which are used to obtain specific functions Each individual unit is known as a ldquohydraulic elementsrdquo One or more combination of these elements is used to get output at required condition to fallow a logical sequence of operation
Based on the functions they perform hydraulic elements are classified as
1 Power generating elements2 Power utilizing elements3 Power control elements4 Accessories
41 POWER GENERATING ELEMENT
In fluid power systems the elements that inject energy in to the transmission system is the pump It draws mechanical energy from rotating shaft and converts it into a combination of potential energy and kinetic energy and delivers pressurized oil at a desired flow rate Commonly hydrostatic or positive displacement pumps are used in hydraulic systems
In these pumps the oil is trapped in discrete segments and then forced out of a pump The flow through these pumps does not vary much except for leakage which is independent of the outlet pressure
42 BASED ON THE BASIC MECHANISM THE PUMPS ARE DIVIDED
INTO
1 Gear pump
2 Vane pump
3 Piston pump
Department of Mechanical engineering Dr Smce 2012 Page 20
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
421 Gear pump
A gear pump develops flow by carrying oil between two teeth of the meshed gears One gear is driven by the drive shaft and rotates the other The pumping chamber formed between the gear teeth are enclosed by the pump housing and side plates A partial vacuum is created at the inlet as the gear teeth unmesh Oil flow in to fill the space and is carried around the outside of gears As the teeth mesh again at the outlet the oil is forced out most gear pumps are of fixed displacement types with a maximum attainable pressure of 80kgfcm2 Fig 41 shows gear pump in operation
422 Vane pump
A vane pump consists of a circular slotted rotor which is splined to the drive shaft and turns inside a cam wing Vanes are fitted to the rotor slots and fallow the inner space of the ring As the rotor turns centrifugal force and the pressure under the vanes hold them out against the ring Pumping chambers are formed between the vanes and are enclosed by a rotor ring and the two side plates At the pump inlet a partial vacuum is created as the space between the rotor ring increases Oil entering is trapped in the pumping chambers and then pushed into the outlet as the space decreases
There are two types of vane pumps Balanced vane pump and unbalanced vane pump
4221 Balanced vane pump
In the balanced type the cam ring is elliptical and permits two sets of internal parts The two outlet parts are 1800 apart so that pressure forces on the rotor are canceled out thus preventing side loading of drive shaft and bearings These pumps works under high speed and pressure condition Fig 42 shows a balanced vane pump
4222 Unbalanced vane pump
In the unbalanced type the shaft is side loaded from the pressure on the rotor The displacement of this pump can be changed through an external control such as hand wheel or a pressure compensator The control moves the cam ring to change the eccentricity between ring and rotor there by reducing or increasing the size of the pumping chamber
Department of Mechanical engineering Dr Smce 2012 Page 21
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
4223 Piston Pump
Piston pump operates on the principle that a piston reciprocating in above will draw in oil when retracted and expel it when moved forward The piston pump comprises of number of cylinders working with suitable pace difference in a cylindrical block giving constant displacement The piston pump has a number of advantages like high volumetric efficiency overall efficiency high working pressure and good slack capabilities Fig shows a piston pump with variable discharge adjustments
43 POWER UTILIZING ELEMENTS
Power utilizing elements are the actuators driven by the regulated pressurized fluid to obtain useful output Depending upon the type of job and the power requirements the actuators are classified as cylinder and motors
431 Cylinders
Cylinders are linear actuators ie the output of cylinder is linear motion The essential parts of the cylinder are a barrel a piston piston rod and caps and suitable seals Barrels usually are seamless steel tubing honed to a fine finish on the inside The piston usually of cast iron ore steel incorporates seals to reduce leakage between it and the cylinder barrel The parts of the cylinder are in the end caps which are attached directly to the end cap of the barrel and secured by bolts Fig of a typical cylinder construction
Various cylinder mountings are provided to obtain flexibility in anchoring the cylinder Rod ends are usually threaded for attachments directly to the load or to accept a clamp or any other coupling device Fig 45 shows various types of cylinder mountings The cylinders are classified as single acting cylinder and double acting cylinder
a) Single acting cylinder A single acting cylinder is operated by oil only on one side of the piston
b) Double acting cylinders a double cylinder is operated by oil on both sides of the piston
Double acting cylinders are further classified as differential and non-differential cylinders In differential cylinders unequal areas are exposed to pressure on either sides of piston In non-differential types equal areas are exposed to pressure on either sides of the piston
Department of Mechanical engineering Dr Smce 2012 Page 22
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
432Hydraulic Motors
Motor is a rotary hydraulic actuator which very closely resembles a pump in construction Instead of pushing the fluid as a pump does the motors are pushed by the fluid and develop torque and continuous rotary motion Motors are classified as gear motors vane motor and piston motors similarly as in pumps
433 Power control elements
The output of power generating element is pressurized fluid at a given pressure and flow rates This should be modified in a controlled manner by adjusting various properties so that it is acceptable to the drive circuit This is accomplished by power control elements
Based on the parameters the control are classified as
1) Direction control valve
2) Flow control valve
3) Pressure control valve
4331 Direction control valves
As the name implies it is used to control the direction of flow Based the number of flow paths direction control valves are divided into two way and four way valves
The basic function of a 2 way valve and four way valve is to direct the inlet flow to either of the outlets parts as shown in fig 46 Flow from the pump part (p) of the valve can be directed either the outlet parts named (A) and (B) as per convenience In the four way valve the alternate part is to tank parts (T) permitting return flow to the reservoir
In most of the valves a cylindrical spool is used for pilot control The spool moves back and forth in machined bore in the valve body Cored or machined passages direct the fluid from the inlet part connections in the body through the angular groves in the spool to the outlet part
43311 Operation Control
Department of Mechanical engineering Dr Smce 2012 Page 23
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Spool valve can be actuated or controlled in a number of ways namely manual mechanical or electrical The common method is with a solenoid using electric energy When current is supplied to the solenoid coil magnetic field is created that drives the armature into the coil
43312 Check Valve
Check valve is one directional valve It permits free flow in one direction and blocks the flow in other direction Fig 48 shows a check valve
4332 Pressure Control Valve
Pressure control valves are used to limit the maximum system pressure regulating reduces power in certain portion of the circuit Their operation is based on a balance and spring force Pressure control valves and classified based on their primary function
a) Relief Valve - The relief valve is a closed valve connected between pressure tank and reservoir its purpose is to limit pressure in the system When the system pressure exceeds the preset maximum then the valve opens directing the flow back to the reservoir when the pressure falls the valve automatically closes and prevents the resulting damage Fig 49 shows a simple relief valve
b) Pressure Reducing Valve - Pressure reducing valves are normally open controls used to maintain reduced pressure in certain portion of the system They are actuated by pressure sensed in the branch circuit and tend to close as it reaches the valve setting Thus preventing further pressure build up A pilot operated pressure reducing valve is shown in fig 410
It has a wide range of pressure adjustments and provides accurate control The operating pressure is set by an adjustable spring in the upper body The valve spool in the lower body adjusts the pressure When the pressure raises to the valve setting the spool moves partly to the outlet block the outlet part Only enough flow is passed to the outlet to maintain the preset pressure
4333 Flow Control Valve
A flow control valve is used to regulate the volume of fluid in the system The speed of actuator is depends on the flow rate of oil There are three types of flow control valves They are by-pass Restricted and temperature compensated valves
a) By-Pass Valve
Department of Mechanical engineering Dr Smce 2012 Page 24
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It combines over load protection with pressure compensated control of flow It has normally closed hydrostat which opens to direct the fluid in excess of the throttle setting back to the tank the work load is sensed in the chamber above the hydrostat and together with a light spring tends to hold it closed Pressure in the chamber below the hydrostat increases due to the restriction of the throttle and causes it to raise diverting any excess flow to tank when the difference in pressure in sufficient to overcome the spring force
Overload protection is come by an adjustable spring loaded poppet which limits the maximum pressure above the hydrostat causing it to function as a compound relief valve whenever work load requirement exceed its setting Fig 411 shows a bypass type control valve
b) Restrictor Type
In this type of valve the hydrostat is normally open and tends close off blocking all the flow in process of throttle setting In these units the work load pressure acts with a light spring above the hydrostat to hold it open Pressure at the throttle inlet and under the hydrostat tends to close it and permitting only that oil to enter the valve Fig 412 shows a restrictor types flow control valve
c) Temperature Compensated Valve
Flow through a pressure compensated flow control valve is subjected to change with variations in all temperature The flow of the oil is maintained at a constant rate even when the temperature increases by decreasing the size of throttle opening This is accomplished through a compensating rod which expands with heat and contracts when cooled The throttle is a simple plunger that moved in and out of the control parts The compensating rod is placed between the throttle and its adjuster Fig 413 shows a temperature compensated valve
434 ACCESSORIES
These are the elements that are utilized in a hydraulic system to obtain certain specific function or to improve the efficiency The commonly used accessories are accumulators pressure gauge pressure switch flow meters etc
4341 Accumulators
These are used in the circuit to perform the following functions
a) To store fluid under pressure
Department of Mechanical engineering Dr Smce 2012 Page 25
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
b) To cushion shock waves in the circuit piping
4342 Pressure gauge- Pressure gauges are used for measuring the pressure of the oil in the system
4343 Pressure switch- They are used as an open and closed electrical switches at selected pressures to actuate solenoid operated valves or to give audible or visual indicators to the operator
5 DESIGN OF HYDRAULIC CIRCUIT
Department of Mechanical engineering Dr Smce 2012 Page 26
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
For the successful operation of a hydraulic system various element and devices must predetermined depending upon the variety of functions needed A system design is based on the desired function in a logical sequence To achieve this flow diagram with all components included is to be drawn Studying of this gives the practical visualization of the operation of the system and thus forms the basis for building a system
Circuit designing implies sizing of various components like actuators pump valves and connecting links Actuators are sized from the load requirements and required system pressure For given load higher supply pressure means a smaller actuator The actuator size should also meet the requirements based on the minimum flow rate that can also be efficiently controlled The load requirement should include the cutting loads frictional forces and pressure losses in valves filters and pipe lines as well as any intended back pressure in the circuit The maximum operating speed determines the maximum flow demand of the actuator The pressure and flow requirements of the individual actuator in the system over a full cycle operation are estimated The maximum simultaneous demand of the system is then determined The power supply given to the system must satisfy the above demand The power supply may be given by a constant delivery pump multi pumps or pressure compensated pumps A combination of these together with accumulators may also be used The mode of supply is decided depending upon the economy of power and minimization of energy waste
The controls valves and filters included in the circuit are to be consistent with the maximum pressure in the flow rate with the maximum pressure and flow rate in the system The pressure drop across the valve and the filters during maximum flow should be as low as possible The connecting lines and passages are sized on the basis of intermissible flow rates The numbers of bends are kept to a minimum Pressure losses in pipe lines and bends are evaluated and suitably compensated Piping should be reduced as far as possible in the system Back mounting and manifolds are to be used to estimate a good deal of external plumbing
Above all the essential requirement is the system should be economical both from the point of view of utilization and construction A minimum number of components are to be used and conservation of energy is to be enhanced But at any time the reliable operation of the system must be kept in mind
51 HYDRAULIC CIRCUIT DIAGRAM
Department of Mechanical engineering Dr Smce 2012 Page 27
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
It is a graphical representation of arrangement of various elements in a hydraulic system Standard symbols are designed for different elements and they are depicted in the circuit diagram Also diameter rate and direction of motion pressure rates etc may be mentioned in the circuit It is accompanied by a part list which gives the type makes and number of pieces of each element in the circuit The standard graphical symbols are shown in the following tables
52 SADDLE MOVEMENT
1 Saddle movement The saddle moment is obtained by a lead screw driven by a feed box or a gear box The different feed rates are obtained by engaging suitable gears in the gear box manually The saddle can be moved rapidly and stalled at any position by rotating hand wheel
Disadvantages of the existing device
1 Need of frequent adjustment to ensure proper functioning 2 Manually operated and operator will get fatigue3 Difficult to maintain accuracy while repeating short and precise cycle4 Slow and laborious operation5 As the operator gets fatigue the operating time of the chuck goes on increases6 No interlock for clamping and spindle rotation
53 DESCRIPTION OF CIRCUIT ELEMENTS
531 PISTON AND CYLINDER
A piston and cylinder arrangement is used to give necessary linear motion Depending upon the forces coming on the tool suitable dimensions for cylinder and piston rod are selected It is connected to the saddle and cylinder is rigidly clamped on the bed The rate of movement of saddle depends upon the flow rate which can be regulated using a flow control valve Minimum feed rate is determined by considering the functional resistance to the motion of saddle to obtain smooth and continuous movement Minimum feed rate can be determined by the rate of flow of oil back pressure in opposite direction and other losses
Department of Mechanical engineering Dr Smce 2012 Page 28
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
532 DIRECTION CONTROL VALVE
Four direction control valves are needed one for rapid moments in forward and reverse direction and the other three for different movements in forward direction
For rapid forward and reverse movements a spring offset two position solenoid operated direction control valve D4 is used For three different feed rates thee solenoid operated three position control direction valve D1 D2 And D3 are used
533 THROTTLE VALVE
To obtain different feed rate flow from these direction control valves these throttle valves are attached to it
534 PRESSURE SWITCH
It is incorporated in the circuit to give an indicator if there is any variation in the working pressure of the system The parameter given to us for the design of hydraulic circuit for the saddle moment of an automatic boring machine were
1 Saddle moment both in forward and reverse direction When the saddle moment is towards the spindle then the speed is both in rapid and in feed
2 Saddle moment is rapid when away from the spindle3 Three different feed selection rates must be available for the saddle which is infinitely
available4 Feed rate 10 to 1500 mmmin5 Rapid rate Forward 45mtmin reverse 6mtmin6 Stroke length = 600mm7 Cylinder diameter = 100mm Piston rod diameter = 50mm8 Cutting force = 2500kgf
54 DESIGN
Weight of saddle = 500kgf
Department of Mechanical engineering Dr Smce 2012 Page 29
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum cutting force encountered = 2500kgf
Frictional force = Weight of saddle times Coefficient of friction
[ Assuming coefficient of friction as 01]
= 500 times 01
= 50kgf
Total force coming on the saddle =
= wt of saddle + cutting force + friction force
= 500 + 2500 + 50
=3050kgf
Taking 25 excess then the actual force coming to account for losses
Net force on saddle = 125 times 3050
= 38125kgf
It is given that base dia is 10cm and piston dia is 5 cm
Therefore area of piston = π4 D2
= π4 (10)2
= 785cm2
Pressure = ForceArea
= 38125
785
= 4856kgfcm2
Taking the working pressure to be 50 kgfcm2
Department of Mechanical engineering Dr Smce 2012 Page 30
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Also effective area on the piston side
= π4 (102 - 52)
= 589cm2
55 SELECTION OF ELEMENTS
1 PISTON AND CYLINDER
Department of Mechanical engineering Dr Smce 2012 Page 31
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A CD 70 series flange mounting cylinder with standard piston rod diameter of 50 mm with a stroke o 600 mm was selected The piston rod has a tie rod end design for coupling
CODE-CD 70 C 10050 ndash 600 Z 102 HCDVT
2 DIRECTIONS CONTROL VALVE
D1 D2 and D3 Three spring offset two position solenoid operated valves are selected
CODE ndash 4WE6C31 ndash G24YNZ4
D4 Spring centered 3 position solenoid operated spool type valve working on 24V DC with hand emergency is selected
CODE ndash 4WE6E31 ndash G24YNZ4
3 THROTTLECHECK VALVE
A throttlecheck valve with flow capacity of 50 ltsmin and a cracking pressure of 15 kgcm2 is selected
CODE ndash MK 8G 12
4 PRESSURE SWITCH
A pressure switch of Bourdon tube with infinitely variable pressure differential with light indicator and lockable type was selected
CODE ndash HED 30 A 3063 ZLQ
56 RATES OF MOTIONS OF SADDLE
Forward Movement
Department of Mechanical engineering Dr Smce 2012 Page 32
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Maximum traverse speed = (Volumemin)(Area of piston)
Maximum traverse speed = 45 mtmins
= 450 cmmin
Therefore Volumemins = maximum traverse speed times area of piston
= 450 times 785
= 35345 cm3min
= 3534 litresmin
Say 36 litmin
Max Feed rate required = 1500 mmmin
= 150 cmmin
Flow required = area of piston times velocity
= 785 times150 = 11775 cm3min
= 117 litin
Minimum feed rate required = 10 mmmin
= 1 cmmin
Therefore flow required = Area of piston times velocity
= 1 times 785 cm3min
= 0078 litersmin
= 008 litersmin
Reverse Movement
Max Traverse speed = 6 mtmin
Department of Mechanical engineering Dr Smce 2012 Page 33
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
= 600 cmmin
Effective area on piston rod side = 589 cm2
Volumemin = Max traverse speed times area of piston
= 589 times 600
= 35345 cm3min
= 3534 litmin
Say 36 litmin
For three different speeds for saddle between the flow rates of 10-1500 mmmin the three direction control valves D1 D2 D3 are used where flow can be adjusted by the three throttle valves attached to them
57 WORKING
The hydraulic circuit for the saddle movement mechanism is shown in figure The oil from the pump is brought to the saddle movement circuit through the pressure line P1
The circuit employs 4 directional control valves D1 D2 and D3 for speed control with different speeds in forward direction and D4 for obtaining rapid movements in forward and reverse direction
When solenoids S4 and S5 of valve D4 are not energized there will be no flow When solenoid S4 is energized the oil takes the path Pb A and oil enters the cylinder through part A hence forward motion is obtained When solenoid S5 is energized the oil takes the path Pb B enters the cylinder through part B hence reverse motion is obtained
When solenoid S1 of valve D1 is not energized there there is no flow When solenoid S1 is energized oil takes path Pa A and flow is established to the cylinder The oil flows through the throttle valve and enters the cylinder through part A Similar is the case with S2 of valve D2 and S3 of valve D3 Depending upon the set flow in throttle valves feed rates are obtained
Pressure switch is used to give an indication of any drop in set pressure in the circuit
Department of Mechanical engineering Dr Smce 2012 Page 34
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
58 WORK CLAMPING DEVICE
581 EXISTING METHOD OF HOLDING THE WORK
The standard practice of holding the work in an engine lathe finds no place in a Fine Boring machine as there is no dead center to support the work at the other end Work is therefore supported at the spindle end by the help of chucks and fixtures
The usual methods of holding work in a Fine Boring machine are
1) Jaw chucks
a) Self centering chucks
b) Independent chuck
c) Combination chuck
d) Air operated chuck
2) Collect chuck
a) push out type
b) Draw in type
c) Dead length type
582 DISADVANTAGES OF THE EXISTING CLAMPING DEVICE
1 It consumes a lot of time to clamp and declamp the tool manually2 There is a lot of strain and fatigue on the operator3 This increases production time and decreases operator efficiency ultimately leading to
loss in productivity
59 REQUIREMENTS OF HYDRAULIC WORK CLAMPING DEVICE
The work holding device must be capable of accommodating different types of work Ease of operation reliability and safety are essential requirements The work should not declamp itself during working and also due to failure of power or
pump
Department of Mechanical engineering Dr Smce 2012 Page 35
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The above functions should be obtained by suitably incorporating electro hydraulic elements in the circuit
510 DESCRIPTION AND FUNCTION OF HYDRAULIC ELEMENTS
5101 ROTARY PISTON AND CYLINDER
A rotary piston and cylinder arrangement is selected to actuate the chuck draw bar which in turn clamps or declamps the work The clamping and declamping force depends on the pressure of fluid and the area on which it acts To obtain the necessary force a pump of suitable pressure and delivery is selected Depending upon the force the diameter of the piston rod and the cylinder are selected
The figure shows a typical rotary cylinder The main parts of the rotary cylinder are
1)Distributor 2) Piston and cylinder
The piston is mounted inside the cylinder and is closed by an end block The piston rod is connected directly to the spindle by means of a tie bar the upper end of the cylinder is connected to a rotary draw tube which rotate in a stationary distributor
Oil is let into the stationary distributor and it fills the annular grooves provided on the stationary draw tube It then flows into the radial port fills the tube and enters the cylinder A thin film of oil is maintained between rotary tube and distributor to provide lubrication and cooling Seals are provided at appropriate places to avoid leakage
RESERVOIR
5102 RESERVOIR
A reservoir having a capacity of minimum three times the required discharge of the fluid with all standard accessories and hydraulic elements are selected
5103 PRESURE REDUCING VALVE
Department of Mechanical engineering Dr Smce 2012 Page 36
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The force exerted on the piston depends upon the pressure To obtain different forces different pressures are needed This is obtained with the help of pressure reducing valve
5104 CHECK VALVE
A direct acting check valve is used to prevent the flow of working fluid in the reverse direction
5104 DIRECTION CONTROL VALVE
The work is clamped and declamped with hydraulic pressure When the solenoid in the directional control valve is not energized the work will remain clamped When the solenoid is energized the declamping takes place The direction controlled valve changes to clamped position when the solenoid is not energized due to the spring
5105 PRESSURE SWITCH
A pressure switch is used to give electrical signal if there is any drop in set pressure in the hydraulic system The electrical signal is utilized later either to stop the operation or to give an audible or visual indication to alert the operator
The parameters given for the design of hydraulic circuit for work clamping device
1 Maximum clamping force = 3000kgf 2 Stroke length = 50 mm3 Safety during power failure4 Safety in case of pressure drops in the circuit5 Clamping force must be variable
511 DESIGN
Maximum clamping force to be exerted = 3000Kgf
Operating pressure = 50kgfcm2
Effective area needed to get clamping force = 300050=60cm2
Department of Mechanical engineering Dr Smce 2012 Page 37
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
As the piston rod dia takes some area also therefore
=1(4timesπ)(D2 ndash d2)
= 60cm2
A standard piston of diameter of 100mm and piston rod of dia 50mm was selected
To check
Effective area = Piston area ndashPiston rod area
= 1(4timesπ)(102 - 602)
= 589cm2
Therefore the piston and the rod diameter selected will satisfy the above requirement
512 SELECTION OF ELEMENTS
5121 ROTARY PISTON CYLINDER
A hydraulic rotary cylinder was utilized A GMT hydraulic cylinder with stroke control unit was selected
Operating pressure = 150 Kgfcm2
Maximum operating pressure = 55kgfcm2
Piston diameter = 100mm
Piston rod diameter = 50mm
Stroke length = 50mm
Maximum RPM = 4000rpm
1 DIRECTION CONTROL VALVE
Department of Mechanical engineering Dr Smce 2012 Page 38
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
A two position spring offset solenoid operated direction control valve working on 24V DC was selected
CODE 4NE6D310FG24YNZ4
2 PRESSURE REDUCING VALVE
A modular pressure reducing valve having maximum secondary pressure of 75kgf cm2 was selected
CODE ZDR6DP2-20754N
3 MODULAR CHECK VALVE
A pilot operated modular check valve was incorporated
CODE Z256-30
4 PRESSURE SWITCH
A pressure switch of bourdon type with an infinitely variable pressure differential
CODE ndash HED30A-3063ZLQ
5 THROTTLE AND CHECK MODULATOR
A device from YUKEN was selected
CODE ndash MSW ndash 01-XD-3080
513 WORKING
The circuit diagram for the work clamping device of a Fine Boring machine is shown in the following figure
Oil from the pressure line comes to the pressure reducing valve and flows to the direction control valve at set pressure
Department of Mechanical engineering Dr Smce 2012 Page 39
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The direction control valve is a two position valve When the solenoid is not energized the oil flows through the check valve enters the cylinder on the piston rod side and exerts the necessary clamping force on the piston thus clamping the job
When the job is to be decamped the solenoid is energized and the oil enters the cylinder on the other side thus exerting necessary decamping force on the piston to release the job
The piston operated modular check valve is adopted which prevents oil from returning back to the tank due to pressure loss in the main line Thus there is no flow of oil in either direction or the job remains clamped thus preventing the resulting damage to the work piece or tool The throttle valve is incorporated to allow the operated to set the speed of the clamping and decamping to the required valve A pressure switch is employed to give an indication of any variation in set pressure
514 POWER PACK ELEMENTS
The elements of power pack are designed depending on the maximum flow rate and maximum pressure This is the total input that is to be given to the two drive circuits
Max Pressure = 50kgfcm2
Max Flow rate required = (36+4) = 40 itsmin
For the above requirements elements were selected has follows
1 PUMP
A variable axial piston pump was selected
CODE YUKEN A16-F-R-01-K-10
Max Pressure (P) = 50 kgfcm2
Maximum displacement = 158 cm3rev
Speed = 400 rpm
Department of Mechanical engineering Dr Smce 2012 Page 40
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
Max Delivery Q = 40 rpm
2 MOTOR
Power required in KW = ( ptimesqtimes10)(102times60)
=(50times40times10)(102times60)
= 327KW
Assuming 70 efficiency = 32707
= 466KW
A 5 KW motor 500 revmin 440380 V was selected
6 CONCLUSION
1) The main aim of our project was to improve the efficiency of the operation and the
operator by utilizing the hydraulic system
2) In this direction some of the operation that is carried out manually was converted into
operations involving hydraulic system
Department of Mechanical engineering Dr Smce 2012 Page 41
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
3) The operation that was carried on in the previous machines involves frequent repetition
with prolonged manual procedure and frequent change of tools and jobsit consumed
more time and induced fatigue in the operator
4) On the contrary the hydraulic system has led to rapid and accurate operations of the
machine which saves time during clamping and declamping operations as they done with
little effort this improves the productivity
5) The other advantages include continuous rates of motion which can be maintained
efficiently and better quality products can be obtained
6) The construction of hydraulic systems is easy as various elements and standard sub-
assemblies are readily available
Further improvements can be effected by utilizing electro hydraulic valves servo valves limit
switches etc
61 DESCRIPTION OF DESIGNED HYDRAULIC SYSTEM
The hydraulic system for saddle movement and work holding device for a fine boring machine is
shown in figure The circuit diagram shows the power pack which supplies pressurized oil for the
system consisting of saddle movement and work clamping device Block lsquoArsquo is meant for saddle
movement circuit and block lsquoBrsquo is meant for work clamping circuit
Department of Mechanical engineering Dr Smce 2012 Page 42
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The required quantity of oil is stored in the reservoir fitted with necessary
accessories like breather filter (3) oil level indicator (2) and return line filter (13)
The pump (4) and motor (6) are mounted on the plate (7) is the heart of the system
which supplies the pressurized fluid A check valve (8) prevents back flow of the oilan
accumulator (10) takes care of the pressure variations and a manually operated shut off valve to
discharge the accumulator Oil from pump is delivered to the two working circuits to the pressure
lines p1 and p2 The discharged oil from the above circuit flows through lines T1 and T2
combines and flows into the reservoir through the return line filter (13) The complete hydraulic
circuit of saddle movement and work clamping device for a fine boring machine is shown in
figure
1 PRESSURE REDUCING VALVE
A pressure reducing valve with set screw for adjustment and with protective cap was selected
CODE - DR 10 DPZ - 2075 YM
2 HYDRAULIC DEVICE
The essential requirements include is ease of operation positiveness and reliability The system must produce the desired functions quickly and economically safety against
overload during operation is essential Considering the above requirements hydraulic systems have an edge over manual
operated ones Job clamping and spindle rotates interlock can be given
62 REQUIREMENTS
The saddle movement is effected by piston and cylinder to give the necessary stroke
Department of Mechanical engineering Dr Smce 2012 Page 43
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44
Design of hydraulic system for saddle movement and work clamping device for a Fine Boring Machine
The saddle movement requires rapid traverse in forward and reverse direction and feed movement in forward direction with provision for stopping the saddle with in the stroke these movements are used for turning and drilling operations
The work clamping device requires oil at different pressures to clamp different jobs with different clamping forces there must also be safety from self-releasing of clamp during operation
Department of Mechanical engineering Dr Smce 2012 Page 44