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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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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

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