2.008 Design & Manufacturing II Spring 2004 Metal Cutting II
Manufacturing Technology II- Notes.pdf
-
Upload
senthil-kumar-subramanian -
Category
Documents
-
view
1.014 -
download
3
description
Transcript of Manufacturing Technology II- Notes.pdf
1
ME 2252 – MANUFACTURING TECHNOLOGY – II II year Mechanical Engg. B-Sec
Notes on Lesson
UNIT – I : THEORY OF METAL CUTTING
Material removal process Types of machine tools
• Turning machines
• Drilling machines
• Boring machines
• Milling machines
• Grinding machines
• Shaping and planing machines
• Gear cutting machines
• Unconventional machining machines
• Special machines like automats, copy turning machines, reaming ,
copy milling machines, centreless grinding machine, broaching
machine etc.
Chip formation
• Discontinuous chip
• Continuous chip
• Continuous chip with built-up edge
Orthogonal cutting
• Mechanics of orthogonal cutting
• Merchant’s cutting force circle
• Orthogonal cutting with shear plane
• Strain and strain rate in orthogonal cutting
www.kinin
dia.co
m
2
Requirement of a cutting tool material Cutting tool materials
• Carbon tool steels
• High speed steel
• Cast cobalt alloys
• Cemented carbides
• Coated carbides
• Ceramics
• Diamond
• Cubic boron nitride(CBN)
Tool wear
• Flank wear
• Crater wear
• Diffusion wear
Tool life
• Taylor’s tool life equation
Surface finish
• Ideal surface finish in turning
Cutting fluids
• Function of a cutting fluid
o Cooling action
o Lubricating action
Types of cutting fluid
• Water based emulsions
• Straight mineral oils
• Mineral oils with additives
www.kinin
dia.co
m
3
UNIT II : CENTRE LATHE AND SPECIAL PURPOSE LATHES Centre lathe – constructional features
• Head stock
• Tail stock
• Bed
• Carriage
• Feed rod
• Lead screw
• Feed change gear box
Lathe specifications
• Distance between centers
• Swing over the bed
• Swing over the cross slide
• Horse power of the motor
• Number of speeds
• Number of feeds
Cutting tools
• Cutting tool geometry
o Back rake angle
o Side rake angle
o End relief angle
o Side relief angle
o End cutting edge angle
o Side cutting edge angle
o Nose radius
www.kinin
dia.co
m
4
Types of tools
• Parting tool
• Turning tool
• Right hand turning tool
• Left hand turning tool
• Radius turning tool
• Thread cutting tool
• Chamfering tool
• Internal turning tool
• Inter facing tool
• Recess or groove making tool
• Internal threading tool
Lathe operations
• Turning
• Facing
• Knurling
• Parting
• Drilling
• Boring
Taper turning methods
• Form tool method
• Compound rest method
• Tailstock set over method
• Using taper turning attachment
Thread cutting method
www.kinin
dia.co
m
5
Special attachments
• Copy turning attachment
• Radius turning attachment
Machining time and power estimation Capstan And Turret Lathe The principle parts are
• Bed
• Head stock
• Cross slide and saddle
• The turret saddle and auxiliary slide
•
Comparison of capstan and turret lathe
S.No. Capstan lathe Turret lathe
1.
2.
3.
Short slide since the saddle is
clamped on the bed in position.
Light duty machine, generally for
components whose diameter is less
than 50mm.
Too much overhang of the turret
when it is nearing cut.
Saddle moves along the bed, thus
allowing the turret to be of large
size.
Heavy duty machine, generally for
components with large diameters
as 200mm.
Since the turret slides on the bed,
there is no such difference.
www.kinin
dia.co
m
6
Automatic lathes Classification
Automatic lathes may be classified based on their
• Size
• Type of blank machined
• Processing capacity
• Machining accuracy obtained
• Principle of operation design features
• Number of spindles and work positions
• Type
Single spindle automates
• Cutting off
• Swiss type
• Automatic screw machine
• Special type
Multiple spindles automates
• Cutting off bar
• Drilling, forming, cutting off bar
• Bar
• Special type
www.kinin
dia.co
m
7
UNIT-III : RECIPROCATING AND MILLING MACHINES Shaper
The main parts of shaper are
• Base
• Column
• Table
• Ram
• Tool head assembly- tool feed handle, tool slide, apron, clapper box, tool
holder
Specifications
• Stroke length
• Length and width of table
• Number of ram double strokes per minute
• Motor horse power
• Range of ram speeds
Planer The main parts of planer are
• Bed
• Table
• Columns or housing
• Cross rail
• Tool head
Specifications
• Dimensions of the table
• Horizontal distance between the two vertical housings
• Length that the table can travel
• Height from top of the table to the top of cross rail
• Type of drive
www.kinin
dia.co
m
8
Types Of Milling Machine
• Column and knee type
o Horizontal
o Vertical
o Universal
o Turret type
Production type
o Simplex
o Duplex
o Triplex
• Planomillers
• Special type
o Rotary table
o Drum type
o Copy milling
o Keyway milling
o Spline shaft milling machine
Horizontal Milling Machine The basic parts of the horizontal milling machine are
• Base
• Column
• Knee
• Saddle
• Table
• Arbor
• Over-arm
• Spindle
www.kinin
dia.co
m
9
Specifications
• The maximum length of longitudinal, cross and vertical travels of the table
and it’s dimensions
• Main drive motor power
• Number of spindle speeds
• Distance from spindle nose to table surface
Milling cutters Based on construction
• Solid
• Inserted tooth type
Based on mounting
• Arbor mounted
• Shank mounted
• Nose mounted
Based on rotation
• Right hand rotation
• Left hand rotation
Based on helix
• Right hand helix
• Left hand helix
Plain milling cutters Side and face milling cutters Slitting saw Special form cutters End mills
www.kinin
dia.co
m
10
Methods of milling
• Upmilling (conventional milling)
• Down milling (climb milling)
Hole making operations The types of hole making operations performed on these holes are
• Drilling
• Boring
• Reaming
• Counter sinking
• Counter boring
• Tapping
Universal Drilling Machine(Radial Drilling Machine) The main parts are
• Base
• Column
• Radial arm
• Drill head
Salient features
Provides movement of the spindle in three directions
Several holes can be drilled on a work piece without moving the same.
www.kinin
dia.co
m
11
UNIT-IV : ABRASIVE PROCESS, SAWING, BROACHING AND GEAR CUTTING Grinding wheel – specification and selection
Abrasive types
• Aluminium oxide
• Silicon carbide
• Cubic boron carbide
• Diamond
Grain size
• Fine
• Medium
• Coarse
Bond
• Vitrified
• Silicate
• Synthetic resin
• Rubber
• Shellac
• Metal
Grade
• Soft
• Medium
• Hard
Structure
• Open
• Medium
• Dense
www.kinin
dia.co
m
12
Grinding wheel types Wheel balancing Dressing and truing
Types of grinding machines
• Cylindrical grinding
• Surface grinding
• Centreless grinding
Cylindrical Grinding Machine The main parts are
• Base
• Tables – lower and upper table
• Head stock
• Tail stock
• Wheel head
Surface grinding machine
• Horizontal spindle and reciprocating table
• Vertical spindle and reciprocating table
• Horizontal spindle and rotating table
• Vertical spindle and rotating table
Centreless grinding machine The main parts are
• Grinding wheel
• Regulating wheel
www.kinin
dia.co
m
13
Types of feed in centreless grinding
• Infeed
• Through feed
• End feed
Honing
Honing is a low abrading process which uses bonded abrasive sticks for
removing stock from metallic and non-metallic surfaces.
The advantages of honing are
• Correction of geometrical accuracy
Out of roundness
Taper
Axial distortion
• Dimensional accuracy
Lapping
Lapping is generally the final finishing operation done with loose abrasive grains.
The process is employed to get
• Extreme accuracy of dimension
• Correction of minor imperfection of shape
• Refinement of the surface finish
• Close fit between mating surfaces
Super finishing Super finishing is another abrasive process which utilizes either a bonded
abrasive like honing for cylindrical surfaces or a cup wheel for flat surfaces. It is
generally used for
• Removing surface fragmentation
• Reducing surface stresses and burns and thus restoring surface
integrity
• Correcting inequalities in geometry
www.kinin
dia.co
m
14
Polishing and Buffing
Polishing is done with a very fine abrasive in loose form smeared on the
polishing wheel with the work rubbing against the flexible wheel. A very small
amount of material is removed in polishing. In buffing the abrasive grains in a
suitable carrying medium such as grease are applied at suitable intervals to the
buffing wheel. Negligible amount of material is removed in buffing while a very
high luster is generated on the buffed surface. The dimensional accuracy of the
parts is not affected by polishing and buffing operations.
Abrasive belt grinding In this process a continuous moving belt with an abrasive is used for grinding the
surfaces. The abrasive belt is normally passed between two wheels with one
being driven while the other remains idle. The workpiece is oscillated across the
face of the abrasive belt to obtain a uniform belt wear and surface finish.
Sawing machines The various types of sawing machines used are
Hack saw
• Manual
• Power
Band saw
• Vertical
• Horizontal
• Contour
Circular saw
www.kinin
dia.co
m
15
Broaching Broaching is a multiple tooth cutting operation with the tool reciprocating similar
to the sawing operations. The similarities end there, since in broaching the
machining operation is completed in a single stroke as the teeth on the cutting
tool called broach, are at a gradually increasing height corresponding to the feed
per tooth of a milling cutter.
Broaching machines
• Push broaching machines
• Pull broaching machines
• Surface broaching machines
• Continuous surface broaching machines
Gear cutting Gear forming Vs Gear generation
Gear shaping Gear hobbing
www.kinin
dia.co
m
16
UNIT-V : CNC MACHINE TOOLS AND PART PROGRAMMING
Numerical Control (N.C)
It can be defined as a programmable automation in which the process is
controlled by numbers, letters and symbols.
Components of N.C
o Program of instructions
o Machine control unit
o Machine tool
N.C. Procedure o Process planning
o Part programming
o Tape preparation
o Tape verification
o Production
Components Of CNC
• A tape reader
• Micro or mini computer
• Computer hardware interface and servo mechanism
• Machine tool
Advantages
• Greater flexibility
• High productivity
• Good reliability
• Metric conversions
• Memory functions
www.kinin
dia.co
m
17
Manual part programming
• Coordinate function
• Feed function
• Speed function
• Tool function
• Preparatory functions
• Miscellaneous functions
• Program number
• Tool length compensation
• Cutter radius compensation
• Canned cycles
Computer assisted part programming Preparing the part programs for CNC machine tools manually is a viable system
for any kind of job. But the assistance of a computer is desirable for part
programming because of a variety of reasons. The first and foremost in this
respect is the complexity of the work piece which makes manufal part
programming a very difficult exercise. Close tolerance contouring to some
mathematically defined, or through a set of points other than a circular arc, is an
example requiring too many coordinate calculations making manual part
programming too tedious to be practicable.
APT language
The complete APT part program consists of the following four types of
statements
• Geometry
• Motion
• Post processor
• auxiliary
www.kinin
dia.co
m