Slider Crank Power Hammer Mechanism Project Report

DEPARTMENT OF MECHANICAL ENGINEERINGBHARATH UNIVERSITY CHENNAI-600073

OCTOBER 2010

BONAFIDE CERTIFICATE

Certified that this project report “SIX BAR SLIDER CRANK POWER

HAMMER MECHANISM” is the bonafide work of “YEMMINA

MADHUSUDHAN” who carried out the project work under my

supervision.

Dr. T.J. PRABHU

HEAD OF THE DEPARTMENT

Mechanical Department

BHARATH UNIVERSITY

173, Agaram road, Selaiyur, Chennai 73.

JOSE ANANTH VINO. V

GUIDE

PROFESSOR

Mechanical Department

BHARATH UNIVERSITY

173, Agaram road, Selaiyur, Chennai 73

AIM:

To design and fabricate a simple mechanical operated power hammer by

applying the principle of kinematic arrangement and machine design concepts.

1. INTRODUCTION TO MECHANISMS

1.1 Concept of degrees of freedom

In the design or analysis of a mechanism, one of the most important concern is the

number of degrees of freedom (also called movability) of the mechanism. It is defined

as the number of input parameters (usually pair variables) which must be

independently controlled in order to bring the mechanism into a useful engineering

purpose.

1.2 Degrees of Freedom of a Rigid Body in a Plane

The degrees of freedom (DOF) of a rigid body are defined as the number of

independent movements it has. Figure 1.2 shows a rigid body in a plane. To

determine the DOF of this body we must consider how many distinct ways the bar

can be moved. In a two dimensional plane such as this computer screen, there are 3

DOF. The bar can be translated along the x axis, translated along the y axis, and

rotated about its centroid.

Fig 1.2 fig 1.3

1.3 Degrees of Freedom of a Rigid Body in Space

An unrestrained rigid body in space has six degrees of freedom: three

translating motions along the x, y and z axes and three rotary motions around the x, y

and z axes respectively in the as shown in the fig 1.3

1

1.4 Kutzbach Criterion Equation

Consider a plane mechanism with number of links. Since in a mechanism,

one of the links is to be fixed, therefore the number of movable links will be ( -1)

and thus the total number of degrees of freedom will be 3(n-1) before they are

connected to any other link. In general, a mechanism with number of links

connected by j number of binary joints or lower pairs (i.e. single degree of freedom

pairs) and h number of higher pairs (i.e. two degree of freedom pairs), then the

number of degrees of freedom of a mechanism is given by

n = 3( -1)-2j-h

This equation is called Kutzbach criterion for the movability of a mechanism

having plane motion.

If there are no two degree of freedom pairs (i.e. higher pairs), then h= 0,

substituting h= 0 in equation 1, we have

n=3( -1)-2j

1.5 Four bar chain mechanism

The simplest and the basic kinematic chain is a four bar chain or quadratic

cycle chain, as shown in below fig. It consists of four links p, q, l and s, each of them

forms a turning pair. The four links may be of different lengths. According to

Grasshof’s law for a four bar mechanism, the sum of the shortest and longest link

lengths should not be greater than the sum of the remaining two link lengths if there is

to be continuous relative motion between the two links.

2

According to Grasshof’s law for a four bar mechanism, the sum of the shortest

and longest link lengths should not be greater than the sum of the remaining two link

lengths if there is to be continuous relative motion between the two links.

A very important consideration in designing a mechanism is to ensure that the

input crank makes a complete revolution relative to the other links. The mechanism in

which no link makes a complete revolution will not be useful. In a four bar chain, one

of the links, in particular the shortest link, will make a complete revolution relative to

the other three links, if it satisfies the Grasshof’s law. Such a link is known as crank

or driver.

1.6 Single Slider Crank Mechanism

A single slider crank chain is a modification of the basic four bar chain. It

consists of one sliding pair and three turning pair. It is, usually, found in reciprocating

steam engine mechanism. This type of mechanism converts rotary motion into

reciprocating motion and vice versa.

In single slider crank chain, as shown in below fig the links 1 and 2, links 2

and 3, and links 3 and 4 form three turning pairs while the links 4 and 1 form a sliding

pair.

The link 1 corresponds to the frame of the engine, which is fixed. The link 2

corresponds to the crank; link 3 corresponds to the connecting rod and link 4

corresponds to cross- head. As the crank rotates the cross-head reciprocates in the

guides and thus the piston reciprocates in the cylinder.

3

2. Study of Power Hammers

Until now we have confined ourselves to study of hand tools used in smithy

work. They certainly perform very well so far as the hand- forging is concerned, but

their use for satisfactory production is limited to small forging only. It would not be

difficult to understand that the intensity of blows, however great one may try to

achieve through hand hammering, will not be sufficient enough to effect the proper

plastic flow in a medium sized or heavy forging. For this, a power hammer is usually

employed. The capacity of these hammers is given by the total weight of their falling

parts i.e., tup or ram and die. A 200 kg hammer will be one of which the falling parts

weigh 200 kg. The heavier these parts and greater the height from which they fall.

The higher will be intensity of blow the hammer will provide. Power hammers in

common use are of different types e.g. spring power hammers, pneumatic power

hammers, Steam hammers and Drop or Forge hammers and six bar slider crank power

hammers. These hammers are named partly after their construction, partly according

to their way of operation. Apart from these, a large number of forging presses and

machines are used in forging work. In the following articles these hammers and

machines will be discussed in detail.

2.1 Types of Power Hammers

2.1.1 Helve hammer

Helve hammers are well adapted for general engineering work where the size

of the stock is changed frequently. They consist of a horizontal wooden helve,

pivoted at one end with a hammer at the other end. An adjustable eccentric raises the

hammer which when falls strikes a blow. They are made in sizes from 5 to 200kg.

2.1.2 Trip Hammer

Trip hammers have a vertically reciprocating ram that is actuated by toggle

connection driven by a rotating shaft at the top of the hammer. Trip hammers are also

4

built in sizes from 5 to 200 kg. The stroke range of both helve and trip hammers

ranges from about 400 per minute for small sizes to about 175 for large size.

2.1.3 Lever-Spring Hammer

They are mechanical driven hammers with a practically constant lift and an

insignificantly variable striking power. It only increases with increasing operating

speed and thus has increases number of strokes per minute. The ram is driven from

rocking lever acting on an elastic rod. The rocking lever consists of a leaf spring so

that an elastic drive is brought about.

They are suitable for drawing out and flattening small forgings produced in

large numbers. Their disadvantage is the frequent breaking of springs due to

vibrations when in operations.

Spring hammers are built with rams weighing from 30 to 250 kg. The number

of strokes varies from 200 to 40 blows per minute.

2.1.4 Pneumatic hammer

The hammer has two cylinders compressor cylinder and ram cylinder. Piston

of the compressor cylinder compresses air, and delivers it to the ram cylinder where it

actuates the piston which is integral with ram delivering the blows to the work. The

reciprocation of the compression piston is obtained from a crank drive which is

powered from a motor through a reducing gear. The air distribution device between

the two cylinders consists of rotary valves with ports through which air passes into

the ram cylinder, below and above the piston, alternately. This drives the ram up and

down respectively.

2.1.5 Hydraulic hammer

In this hammers instead of air oil was used. The cost hydraulic hammer is

high as compared to the pneumatic hammers. Hydraulic hammer is used in high force

applications. These are noise less.

5

3. PRESENT SCENARIO OF POWER HAMMER AND

MECHANISMS

3.1 Power hammers

Unfortunately, using presently available power hammers and formers can

subject users to a number of inherent disadvantages. Generally, presently available

power hammers and formers are expensive and may cost on the order of tens of

thousands of dollars putting them out of reach of all but the largest metalworking

operators. Presently, available power hammers and formers tend to be bulky and

occupy large footprints making them unsuitable for small-scale operations. In

addition, presently available power hammers and formers can require precise, custom

machined die sets, which may be unusable with other machinery, in order to provide

proper operational clearance. Finally, presently available power hammers and formers

can be operated by linkage drives that have the capacity to literally destroy the

machines if proper die set-ups and clearances are not maintained.

Recent research of power hammer

The present disclosure addresses a power hammer assembly providing users

with the metal forming advantages associated with power machinery at a reduced

expense and in a smaller footprint than presently available power hammer systems. In

general, the power hammer assembly of the present invention provides three-

dimensional shaping capabilities, which have application in the forming of custom

metal products such as, for example, customized motorcycle and automotive parts.

The power hammer assembly of the present disclosure can be fabricated and

assembled in a kit fashion with commonly available tools to reduce costs.

Alternatively, the power hammer assembly of the present disclosure can be purchased

in an assembled configuration. In one aspect, a power hammer assembly of the

present disclosure provides powered forming capabilities while remaining economical

with respect to performance, vibration, and footprint size and acquisition costs. In

6

some embodiments, the power hammer assembly can comprise a power assembly for

providing a single stroke speed and/or a single set stroke with respect to the striking

of die assemblies against a piece of metal. In some embodiments, the power hammer

assembly of the present invention can comprise a larger throat area and/or a larger die

gap than presently available power hammers to facilitate ease of use. In some

embodiments, the power hammer assembly of the present invention can comprise

adjustment features allowing for the use of die sets of varying configurations such as,

for example, shank size, shank length or alternatively, die sets fabricated for use with

other machinery. In some embodiments, the power hammer assembly of the present

invention can comprise a belt transmission assembly designed to slip in the event of

die interference during set-up or operation so as to avoid damaging the power

hammer assembly. In some embodiments the power hammer assembly of the present

invention includes fine adjustment means for spacing between the upper and lower

die.

3.2 Mechanism

Four bar parallel linkage mechanism for toe movement

In recent research the four bar linkage mechanism is used for the humanoid

robots for the free movement of their toe. Using this mechanism the major part of the

force acts on the non-movable portion of this link rather then on the toe tip. Because

of this it is possible to decrease the constraint on the joint. At the same time the

following multiple roles of the toe are expected. One it to generate a large kicking

force at the toe pad and another is to maintain multiple contact with the floor by the

toe joint control.

7

4. SIX BAR SLIDER CRANK POWER HAMMER

MECHANISM

4.1 Construction

As shown in above diagram it consists of 5 links, and one fixed link. The five

links are crank (link 1), link 3. Connecting rod (link 4), Crank (link 5) and Ram die

(link 2).Column can be considered as a fixed link. The link 1 rotates about a turning

pair F, it is rotated by a pin joint axis, the link 3 and link 1 is connected by a turning

pair E. The connecting rod (link 4) and link 3 are connected by a turning pair D. The

crank (link 5) is fixed at a turning pair A and oscillates about the pin joint axis. Crank

(link 5) and connecting rod (link 4) are connected by a turning pair B.

Ram Die (link 2) and connecting rod (link 4) are connected by a sliding pair

C. Ram Die and composite bush are connected by a sliding pair G.

Crank (link1) is joined at turning pair F to the column and also crank (link 5)

is joined at turning pair A. Column is welded to the base, vice (not shown in above

8

fig) is fitted to the column for holding the work piece. All the links, Column, Base

and Vice are made up of Mild Steel, they are rigid enough to absorb the vibrations

and shocks produced during work. Composite bush is made up of two materials outer

one is of Mild Steel and the liner is made up of Gun Metal to prevent from wear, tear

and corrosion resistance. A handle is provided at point E, with the help of the handle

the crank (link 1) is rotated.

4.2 Working Principle

The Crank (link 1) rotates at a fixed axis at F it is joined to link 3. As the link

1 is rotated the motion is transmitted to the link 3 which is connected at point E. The

motion is further transmitted to the connecting rod which is joined with the link 3 at

D. Finally the connecting rod transmits the motion to the Ram Die (link 2) which

reciprocates at a fixed path G. The Connecting rod (link 4) and Ram Die (link 2) are

connected at C, Where a slot is provided for getting a straight line motion of the ram

Die. The crank (link 5) is provided for oscillating the connecting rod at a fixed path.

4.3 Manufacturing Process

4.3.1 Cranks (link 1 and 5)

A mild steel material of the required dimension is cut on the power hack saw

machine. After cutting process is over the fillet is provided over the edges by using a

hand grinder. After a drill of diameter 6 mm is made. Finally the filing was done on

the bench vice.

4.3.2 Connecting Rod

A mild steel material of the required dimension is cut on the power hack saw

machine. After cutting process is over the fillet is provided over the edges by using a

hand grinder, after providing fillets drilling operation of required diameter is done

9

after completing this process now we proceed towards milling the slot of 65 x 8 x 6

mm3 by using an end mill cutter. Finally filing was done on bench vice to remove

unnecessary sharp corners.

4.3.3 Ram die

Mild steel material of required dimension is cut on power hack saw. The

material was fixed on the chuck in a lathe machine for doing facing and turning

operations. Polishing was done for good surface finish. Chamfers were made for

removing sharp corners. A hole was drilled at the end of the ram of the required size

for fixing the slider pin. A slot was milled on the rod to insert the connecting rod in

the slot and fixing it in the slider pin. At the other end of the ram a hole of required

size was made and then later it was taped at the same end to make the fixing

adjustment of the punch with the help of a screw.

4.3.4 Composite Bush

It was manufactured by two different materials one of Mild steel and other

was liner made up of Gun metal. The outer one is made up of Mild steel on which

facing and turning operations were done on a lathe and then the inner one was made

up of Gun metal on which facing and turning were carried out of the required size

then the liner was inserted in the outer bush by the application of a press fit.

4.3.5 Column

The Column is made up of Mild Steel of required dimension. First the

marking for the holes to fix the links were done on the column. The outer profile was

marked and then made to cut on a gas cutter, and then it was milled to the required

size and then finally chamfering was done to remove unnecessary sharp corners and

edges. Drills were drilled on the column for bearings, turning pairs F and A. Then the

composite bush was welded on the column. Vice was fitted on the column by the

application of welded joints for holding the work piece.

10

4.4 Determination of Degrees of Freedom

The formula for finding the degree of freedom from the Kutzbach equation is

given below

n = 3( -1)-2j-h

Where,

n = Degree of freedom

= no of links

j = no of lower pairs

h = no of higher pairs

Links:

a) Fixed link

b) Crank (link 1)

c) Crank (link 5)

d) Link 3

e) Connecting Rod

f) Ram Die

Therefore, number of links = 6

Lower pairs:

a) Turning pair F

b) Turning pair E

c) Turning pair D

d) Turning pair A

e) Turning pair B

f) Sliding pair C

g) Sliding pair G

Therefore, number of lower pairs = 7

Number of higher pairs = 0

11

Therefore, n = 3( -1)-2j-h

h = o

n = 3( -1) -2j

n = 3(6-1) -2 x 7

n = 3 x 5 – 2 x 7

n = 15 – 14

n = 1

Therefore, the mechanism has single degree of freedom.

4.5 Applications

4.5.1 Forging

Forging refers as the process of plastically deforming metals or alloys to a

specific shape by a compressive force exerted by some external agency like hammer,

Press, rolls, or by an upsetting machine of some kind. The portion of a work in which

forging is done is termed the forge and the work is mainly performed by means of

heavy hammers, forging machines, and presses. Forging processes are among the

most important manufacturing techniques since forging is used in small tools, railroad

equipment, automobile, and aviation industries.

A number of operations are used to change the shape of the raw material to the

finished form. The typical forging operations are:

1. Upsetting.

2. Fullering.

3. Drawing down.

4. Setting down.

5. Punching.

6. Bending.

7. Welding.

8. Cutting.

12

All these operations are carried out with the metal in a heated condition,

which must be maintained by taking a ‘fresh’ heat when the work shows sign of

getting cold.

Forging Processes

The processes of reducing a metal billet between flat-dies or in a closed-

impression die to obtain a part of predetermined size and shape are called smith

forging and impression-die forging respectively. Depending on the equipments

utilized they are further sub-divided as hand forging, hammer forging, press forging,

drop forging, mechanical press forging, upset or machine forging.

In general, the methods of forging may be classified as follows:

4.5.2 Press

Press working involves production of final component from sheet metal in

cold condition. The machine which is used to apply the required pressure of force in a

FORGING PROCESS

SMITH IMPRESSION

DIE

Hand Power Drop Press Machine

Hammer

Press

13

short duration is called press. The press consists of a frame, supporting bed and ram.

The ram is equipped with special punches and moves towards and into the die block

which is attached to a rigid body. The punch and die block assemble are generally

referred to as a die set or simply die.

A disadvantage of press working is that the operations are carried out at

room temperature and the metal is less deformable of strain hardening.

Classification of Presses

Presses are classified in various ways as listed below.

(i) Mechanical press.

(ii) Hydraulic press.

Press Tool Operations

A large number of operations can be performed by using press tools, and all

press tool operations can be broadly classified into two types.

1. Cutting operations.

(i) Blanking,

(ii) Piercing

(iii) Lancing,

(iv) Cutting off and Parting,

(v) Notching,

(vi) Shaving, and

(vii) Trimming.

2. Shaping operations

(i) Forming (embossing, Beading and Cutting, Bulging etc.),

(ii) Drawing, and

(iii) Bending.

14

II. DESIGN CALCULATIONS

1. Determination of length of the links

For evaluating the length of the links we made prototype, Length of the links

is proportionally taken according to the diagram of the Six bar Slider crank Power

hammer mechanism. By checking the movability after more and more trails of link

lengths we finalized the dimensions as shown below

1. crank (link 1) = 120mm

2. Ram die link2 = 420mm

3. link3 = 440mm

4. connecting rod(link4) = 655mm

5. crank (link 5) = 120mm

2. Design calculation for finding the width and thickness of the

links

This mechanism is designed for applying a compressive force of 0.6 tonnes for

forging or press operation.

Minimum cross sectional area required to transmit is 0.6 tonnes load (A):

The formula for the minimum effective area is obtained as bt – (dt) it can be

observed in the link as in the fig2.1

15

Fig 2.1

In fig 2.1 hatched portions indicates minimum effective cross sectional area in the

entire mechanism. We know that stress is inversely proportional to the area, so the

minimum area leads to increase the stress. So it is always preferred to design any

machine by taking minimum cross sectional area as effective area.

For safe design

16

From the design of bolt we obtained diameter of pin as 6mm, by keeping the diameter

of pin constant and by trail and error method we obtained the breadth and thickness of

the link as 20mm and 6mm respectively.

3. Design calculation for bolt diameter

3.1 Calculation of Stress Concentration

Stress concentration factor is given by,

Kt =

Nominal stress is given by,

The below diagram is for the finite width plate with a transverse hole.

We know that width of the plate W = 20mm

Thickness of the plate h = 6mm

Nominal stress is given by,

Where,

17

P = tensile force

= 0.6 tonne

= 0.6 1000 9.81

= 5886N

Therefore,

Kt =

=

= 65.22

5886 = 65.22(120-6a)

5886 = 7826.5 – 391.32a

5886 – 7826.5 = - 391.32a

- 1940.5 = - 391.32a

Therefore a =

a = d (diameter) = 4.99mm

Due to dynamic characteristics of links the diameter of pin is selected as 6 mm.

3.2 Calculation for bearing stress.

For M.S material = 300 N/

Factor of safety = 2

Permissible bearing of crushing stress =

18

= 300/2 = 150N/

Bearing stress

P = 0.6 + 1000 9.81N

d = 6mm

t = 6mm

n = 2

81.75 N/

The bearing stress is greater than 81.75 N/ , so the design is satisfactory.

4 Design for punching operation

Permissible shear stress is given by,

= 0.6 300

= 180 N/

Shear area for punching operation can be observed from above diagram is

Where, d = diameter of blanking or piercing hole in mm.

t = the thickness of the blank in mm.

19

Shear area = =

= 33.3

Therefore t =

t = 1.5mm

III. OPERATION SHEETS

1. CRANK (LINK 1)

20

Description : Crank 1

Part No : 1

Material : Mild Steel.

Required size : 120mm x 20mm x 6mm

SL. NO MACHINE OPERATION TOOL GAUGE

1 Power saw Cutting Hacksaw

Vernier

caliper, steel

rule

2 Grinding FilletGrinding

wheel

3 Drilling Drill 6 x 6 Drill bitVernier

caliper

4 Drilling Drill 6 x 6 Drill bit Vernier

caliper

5 Bench vice Filing Flat file

2. RAM DIE

Description : Die

Part No : 2


21

Required size : 20mm x 420mm


1 Power saw CuttingHacksaw

blade

Vernier caliper,

steel rule

2 Lathe FacingSingle point

cutting toolVernier caliper

3 Lathe Drilling 10x25 Drill 20 Vernier caliper

4 Drilling Drill 4.5 x 5 Drill 4.5 Vernier caliper

5 Drilling Drill 6 x 6 Drill 6 Vernier caliper

6 TappingM6 internal

threadTap

7 Milling Slot End mill

cutterVernier caliper

3. LINK 3

Description : LINK 3

Part No : 3


22




Vernier

caliper, steel

rule


wheel


caliper


caliper


4. CONNECTING ROD

Description : Connecting Rod

Part No : 4



23



Vernier

caliper, steel

rule


wheel


caliper


caliper

5 Milling Slot End mill cutterVernier

caliper


5. CRANK (LINK 5)

Description : Crank (link 5)

Part No : 5



24



Vernier

caliper, steel

rule


wheel


caliper


caliper


6. COMPOSITE BUSH

Description : composite bush

Part No : 6

6.1 Bush.

25

Material : Mild steel

Required size : 38mmx 100mm



Vernier

caliper,

steel rule


cutting tool

Vernier

caliper

3 Lathe Drill 25 Drill bitVernier

caliper

4 Lathe Reaming ReamerVernier

caliper

6.2 Liner

Material : Gun metal

Required size : 25mm x 105mm



Vernier

caliper,

steel rule

26


cutting tool

Vernier

caliper

3 Lathe Drill 25 Drill bit Micrometer

4 Lathe Reaming Reamer Micrometer

5 Lathe Step turningSingle point

cutting tool

Vernier

caliper

7. COST ESTIMATION

7.1 Cost of Standard components

Name of component Quantity Cost/piece Cost in Rupees

Bearing (6mm) 4 15 60

M6 bolt and nut 5 8 40

½ inch bolt and nut 1 26 26

M5 Countersunk bolt 8 1.5 12

27

and nut

M6 Countersunk bolt

and nut 2 3 6

TOTAL COST 144

7.2 Material Cost

Name of component Quantity Cost in Rupees

M.S Flat for links 1 150

M.S Rod for ram 1 100

M.S sheet for base 1 2000

Bush (M.S and gunmetal) 1 156

TOTAL COST 2406

7.3 Machining Cost

Machine Cost in Rupees

Lathe 500

Drilling 300

Gas Cutting 170

Welding 200

Milling 660

Total Cost 1830

28

7.4 Total Cost of Six bar Slider Crank Power Hammer

Mechanism

Particulars Cost in Rupees

Transportation and Allowances 1220

Painting and Name Plate 800

Cost of Standard Components 144

Material Cost 2406

Machining Cost 1830

Total Cost 6400

29

PART AND ASSEMBLY DRAWINGS

30

Slider Crank Power Hammer Mechanism Project Report

Documents

Transcript of Slider Crank Power Hammer Mechanism Project Report