Machine Tools Theory and Q&A.pdf

NTMMNTMM

By S K MondalBy S K Mondal

Need for Unconventional ProcessesNew materials having high strength and hardness, such as

nimonic alloys and alloys with alloying elements such asnimonic alloys and alloys with alloying elements such as

tungsten, molybdenum, and columbium are difficult to

machine by the traditional methods.

By conventional machining the MRR reduces with an

increase in the work material hardnessincrease in the work material hardness.

Need for development of non‐traditional machiningp g

processes which utilize other methods such as

electrochemical processes for the material removal.

Need for Unconventional ProcessesComplex shapes.

A very high accuracy is desired besides the complexity of

h f b hi dthe surface to be machined.

In Unconventional MachiningDiff f f di l li d hDifferent forms of energy directly applied to theworkpiece to have shape transformation or materialremoval from work surface.No chips No lay pattern on work surface no directNo chips, No lay pattern on work surface, no directphysical contact between the tool and the workpiece .h l l d h b h d h hThe tool material does not have to be harder than the

work material.Tool forces do not increase as the work material getsharderharder.Economic metal removal rate does not decrease as thework material gets harder.

l f fClassification of NTMMTh N di i l M hi i M h d l ifi dThe Non‐traditional Machining Methods are classifiedaccording to the major energy sources employed inmachining.

Th l E M h d1. Thermal Energy Methods

El t Ch i l E M th d2. Electro ‐ Chemical Energy Method

3 Chemical Energy Methods3. Chemical Energy Methods

4 Mechanical Energy Methods4. Mechanical Energy Methods

h l h d1. Thermal Energy MethodsElectrical discharge machining (EDM)

Laser beam Machining (LBM)

Plasma Arc Machining (PAM)

( )Electron Beam Machining(EBM)

I B M hi i (IBM)Ion Beam Machining (IBM)

2. Electro ‐ Chemical Energy MethodElectro‐Chemical Machining (ECM)

Electro‐Chemical grinding (ECG)

Electro‐Chemical Honing (ECH)

Electro‐Chemical Deburring (ECD)

h l h d3. Chemical Energy MethodsTh h d i l ll d hi f hThese methods involve controlled etching of theworkpiece material in contact with a chemical solution.

Chemical Machining Method (CHM)Chemical Machining Method (CHM).

For-2013 (IES, GATE & PSUs) Page 1

h l h d4. Mechanical Energy MethodsUltra Sonic Machining (USM)

Abrasive Jet Machining (AJM)

Water Jet Machining (WJM)

bSome ObservationsEDM h th l t ifi i t dEDM has the lowest specific power requirement and canachieve sufficient accuracy.ECM has the highest metal removal rate, MRR.USM and AJM have low MRR and combined with highJ gtool wear, are used for non‐metal cutting.LBM and EBM have high penetration rates with lowLBM and EBM have high penetration rates with lowMRR and, therefore, are commonly used for microdrilling sheet cutting and weldingdrilling, sheet cutting, and welding.CHM is used for manufacturing PCB and other shallow

tcomponents.PAM can be used for clean, rapid cuts and profiles inalmost all plates upto 20 cm thick with 5o to 10o taper.

h b lShapes Cutting CapabilityTh i NTMM h i l h iThe various NTMM have some special shape cuttingcapability as given below:

1. Micro‐machining and Drilling : LBM and EBM

2. Cavity sinking and standard Hole Drilling: EDM and

USM

3. Fine hole drilling and Contour Machining: ECM

4. Clean, rapid Cuts and Profiles: PAM

5. Shallow Pocketing: AJM

fLimitations of NTMMExpensive set up, low MRR and skilled labour required.

The limitation of electrical machining methods is that

h k i l b l i l d Althe work material must be an electrical conductor. Also,

consumption of electrical energy is very largeconsumption of electrical energy is very large.

The NTMM which have not been proved commerciallyThe NTMM which have not been proved commercially

economical are: USM, AJM, CHM, EBM and PAM.J

ECMECM


l h l hElectrochemical MachiningEl h i l hi i i h f lElectrochemical machining is the reverse of electroplatingThe work‐piece is made the anode, which is placed inclose proximity to an electrode (cathode) and a high‐close proximity to an electrode (cathode), and a highamperage direct current is passed between them throughan electrol te such as salt ater flo ing in the anodean electrolyte, such as salt water, flowing in the anode‐cathode gap.Metal is removed by anodic dissolution and is carriedaway in the form of a hydroxide in the electrolyte foraway in the form of a hydroxide in the electrolyte forrecycling or recovery.MRR i ECM d d t i i ht f k t i lMRR in ECM depends on atomic weight of work material

Fig- Electrochemical Machining process

l h l hElectrochemical MachiningV i i i h d i ill l i kVariation in the current density will result in worktaking the electrodes shape.The electrode is fed with a constant velocity, and theelectrolyte is fed through the toolelectrolyte is fed through the tool.

ECM Equipment


ECM EquipmentS l V l V DC d C ASupply Voltage 2 to 35 V DC and Current 500 to 40,000 AThe tool‐to‐work gap needs to be maintained at a veryg p ysmall value 0.1 to 0.25 mm. A servo drive is provided onthe tool axis for this purposethe tool axis for this purpose.The electrolyte needs to be pumped through this gap ath h f hhigh pressures ranging from 0.70 to 3.00 MPa. Thisintroduces a large amount of load on the machine,because of the large working areas involved. Hence themachine structure will have to be made rigid to amachine structure will have to be made rigid to awithstand such forces.

ECM EquipmentTh l l i f h l d b i dThe electrolyte consists of the metal debris removedfrom the anode, which will have to be filtered before it isre‐pumped into the system.Also a large amount of heat is generated during theAlso a large amount of heat is generated during theelectrolysis, which heats up the electrolyte, and hence itneeds to be cooledneeds to be cooled.

l lElectrolyteTh l t l t i h th t th d ( k i )The electrolyte is so chosen that the anode (workpiece)is dissolved but no deposition takes place on the cathode(t l)(tool).

Properties electrolyte should be1. High electrical conductivity2 Low viscosity2. Low viscosity3. High specific heat

h l b l4. Chemical stability5. Resistance to formation of passivating film on5 p g

workpiece surface6 Non‐corrosive and non‐toxic6. Non corrosive and non toxic7. Inexpensive and readily available

For ECM of steel NaCl is used as the electrolyte.

T lToolTh ti f t l t i l h ld bThe properties of tool materials should be:

1. High electrical and thermal comductivityg y

2. Easy machinability

3. Good shiffness

4. High corrosion resistance

Tool materials: Copper brass bronze Al StainlessTool materials: Copper, brass, bronze, Al, Stainless

Steel, Cupro nickel, etc.

Material wear / Tool wear: Infinite

Advantages1. Complex three‐dimensional surfaces can be machined

accurately. Good for low machinability or complicatedy y pshapes.

2 As ECM leads to atomic level dissolution the surface2. As ECM leads to atomic level dissolution, the surfacefinish is excellent (Ra 0.2 to 0.6 μm) with almost stressf hi d f d i h h lfree machined surface and without any thermaldamage.

3. The tool wear is practically nil which results in a largenumber of components produced per toolnumber of components produced per tool.

4. MRR is highest (1600 mm3/min) among NTMM andbl h l hcomparable with conventional machining.

DisadvantagesU f i di l t l t k it diffi lt t1. Use of corrosive media as electrolytes makes it difficult tohandle.Sh i i d d ( di )2. Sharp interior edges and corners (< 0.2 mm radius) aredifficult to produce.V i hi3. Very expensive machine.

4. Forces are large with this method because of fluid pumpingforces.

5. Very high specific energy consumption (about 150 times5 y g p gy p 5that required for conventional processes),

6. Not applicable with electrically non‐conducting materialspp y gand jobs with very small dimensions

7. Lower fatigue strength7 g g

lApplicationsAny electrically conductive work material irrespectiveAny electrically conductive work material irrespectiveof their hardness, strength or even thermal properties.The machining surface can be situated at anyThe machining surface can be situated at anyinaccessible.Shape application blind comple ca ities cur edShape application – blind complex cavities, curvedsurfaces, through cutting, large through cavities.It i d f th hi i f th t bi bl dIt is used for the machining of the gas turbine blades.Die sinkingProfiling and contouringTrepanningp gGrindingDrillingDrillingMicro‐machining

l lECM CalculationsF d ’ l t t th tFaraday’s laws state that,

ItEm = ItEF

Where m = weight (g) of a materialF

g gI = current (A)t = time (sec)t = time (sec)E = gram equivalent weight of the

t i lmaterialF = constant of proportionality –

Faraday (96,500 coulombs)For-2013 (IES, GATE & PSUs) Page 3

l lECM Calculations

MRR = =EI A Ig / s g / sMRR = g / s g / sF F.V

If you put E = equivalent weight in CGS i.e. g/moleI i A (A)I in Ampere (A)F = 96500 columb/mole i. e. As/mole9 5 / /The MRR will be in g/s

l lECM Calculations

‐3

l lECM CalculationsMRR f lMRR for pure metal

⎛ ⎞ ⎛ ⎞3 3AI cm EI cm⎛ ⎞ ⎛ ⎞=⎜ ⎟ ⎜ ⎟ρ ρ⎝ ⎠ ⎝ ⎠

AI cm EI cmvF sec F sec

MRR for Alloy

ρ ρ⎝ ⎠ ⎝ ⎠vF sec F secy

⎛ ⎞⎜ ⎟

3eqE I cm

⎜ ⎟ρ ⎝ ⎠eqF sec

⎛ ⎞⎜ ⎟∑ ix100 ⎛ ⎞

⎜ ⎟∑ i ix v100= ⎜ ⎟ρ ρ⎝ ⎠∑ i

ieq i

⎛ ⎞= ⎜ ⎟

⎝ ⎠∑ i i

ieq iE Aand

l lFlow analysisT l l h fl id fl i d h h hTo calculate the fluid flow required, match the heatgenerated to the heat absorbed by the electrolyte.

Neglecting all the heat lossesg g

2e e B ol R q c ( )= ρ θ −θe e B oq ( )ρ

OvervoltageOvervoltageIf the total over voltage at the anode and the cathode isIf the total over voltage at the anode and the cathode isΔV and the applied voltage is V, the current I is givenbyby,

RVVI Δ−

=

Dynamics of Electrochemical Machining

Schematic representation of the ECM process with nofeed to the toolf

Electrochemical Grinding (ECG)I ECG th t l l t d i t ti t l b d dIn ECG, the tool electrode is a rotating, metal bonded,diamond grit grinding wheel.A h l i fl b h k i d hAs the electric current flows between the workpiece and thewheel, through the electrolyte, the surface metal is changedto a metal oxide which is ground away by the abrasives Asto a metal oxide, which is ground away by the abrasives. Asthe oxide film is removed, new surface metal is oxidized andremovedremoved.ECG is a low‐voltage high‐current electrical process.Th f h b i i i h ffi i f hThe purpose of the abrasive is to increase the efficiency of theECG process and permit the continuance of the process.h b l l d lThe abrasive particles are always nonconductive material

such as aluminum oxide, diamond, or borazon (CBN). Thush i l i i i i i fthey act as an insulating spacer maintaining a separation offrom 0.012 to 0.050 mm between the electrodes.

Equipment setup and electrical circuit for electrochemical grinding.

l h l d ( )Electrochemical Grinding (ECG)The process is used for shaping and sharpeningThe process is used for shaping and sharpeningcarbide cutting tools, which cause high wear rates on

i di d h l i l i diexpensive diamond wheels in normal grinding.Electrochemical grinding greatly reduces this wheelwear.Fragile parts (honeycomb structures), surgical needles,and tips of assembled turbine blades have been ECG‐processed successfully.p yThe lack of heat damage, burrs, and residual stresses isvery beneficial particularly when coupled with MRRsvery beneficial, particularly when coupled with MRRsthat are competitive with conventional grinding butwith far less wheel wearwith far less wheel wear.


Other Electrochemical processesOther Electrochemical processesEl h i l li hiElectrochemical polishing

Electrochemical hole‐drilling

Electrochemical Deburring

h l lPhysical PrincipleB iBasic process

h l lPhysical PrincipleA j b i l h h f lAn arc jumps between two points along the path of leastresistance.

h l lPhysical PrincipleTh f h i d h i hThe energy of the arc is so concentrated that it causes theelectrode, and the work to melt. But the electrodematerial is chosen so that it melts less.

h l lPhysical PrincipleTh l d di l i fl id i l i dThe metal and dielectric fluid is partly vaporized,causing sudden expansion.

h l lPhysical PrincipleTh bl f h di k kThe blast from the expanding vapors knocks somemolten particles loose, and the remaining molten metalhardens.

h fCharacteristics of EDMM h i f i l l l i dMechanics of material removal ‐ melting andevaporation aided by cavitation.The process is based on melting temperature, nothardness so some very hard materials can be machinedhardness, so some very hard materials can be machinedthis way.h h h h l d b % fThe arc that jumps heats the metal, and about 1 to 10% of

the molten metal goes into the fluid. The melted metalthen recast layer is about 1 to 30 μm thick, and isgenerally hard and rough.generally hard and rough.The electrode workpiece gap is in the range of 10 μm to100 μm.

h fCharacteristics of EDMU V l f 6 V i i l iUses Voltage of 60 to 300 V to give a transient arc lastingfrom 0.1 μ s to 8 ms.Typical cycle time is 20 ms or less, up to millions ofcycles may be required for completion of the partcycles may be required for completion of the part.Rotating the wire in an orbital direction will,‐ Increase accuracy in form and surface finish‐ Decrease electrode wear‐ Decrease electrode wear

Surface finish obtained 0.25 μm


EDM ToolP i i EDM l M i lPrime requirements EDM tool Material

1. It should be electrically conductive.y2. It should have good machinability, thus allowing

easy manufacture of complex shapeseasy manufacture of complex shapes.3. It should have low erosion rate or good work to tool

wear ratio.4 It should have low electrical resistance4. It should have low electrical resistance.5. It should have high melting point.6. It should have high electron emission.

EDM ToolTh l h i f l ( l d ) i l The usual choices for tool (electrode) materials are

Copper, pp ,brass, ll f i d i alloys of zinc and tin, hardened plain carbon steel, p ,copper tungsten, lsilver tungsten,

tungsten carbide, tungsten carbide, copper graphite, and graphite.

Wear Ratio O j d b k f EDM i h hOne major drawback of EDM is the wear that occurs onthe electrode at each spark. Tool wear is given in terms ofwear ratio which is defined as,

Volume of metal removed workWear ratio =Volume of metal removed tool

Wear ratio for brass electrode is 1: 1 For most other

Volume of metal removed tool

Wear ratio for brass electrode is 1: 1. For most othermetallic electrodes, it is about 3: 1 or 4: 1.

h h ( h h h h l )With graphite (with the highest melting point, 3500°C),the wear ratio may range from 5: 1 up to 50: 1.y g 5 p 5

hServo‐MechanismThe gap between the tool and work has a critical

h k h d himportance. As the workpiece is machined, this gap

tends to increase For optimum machining efficiencytends to increase. For optimum machining efficiency,

this gap should be maintained constant. This is done bythis gap should be maintained constant. This is done by

servo‐ mechanism which controls the movement of the

electrode.

l l dDielectric FluidFl id i d t t di l t i d t h lFluid is used to act as a dielectric, and to help carry awaydebris.If the fluid is pumped through and out the end of theelectrode, particles will push out, and mainly collect atthe edges. They will lower the dielectric resistance,resulting in more arcs. As a result the holes will beconical.If fluid is vacuum pumped into the electrode tip, straightu d s vacuu pu ped to t e e ect ode t p, st a g tholes will result.Quite often kerosene‐based oilQuite often kerosene‐based oil.The dielectric fluid is circulated through the tool at a

f N/ 2 l T f it f d dpressure of 0.35 N/m2 or less. To free it from erodedmetal particles, it is circulated through a filter.

lRelaxation circuit

Fig-Relaxation circuit used for generating the pulses in EDM process

dAdvantagesH d t h b ittl f th t i l1. Hardness, toughness or brittleness of the material poses noproblems. Due to this EDM can be used for machiningmaterials that are too hard or brittle to be machined bymaterials that are too hard or brittle to be machined byconventional methods.The method does not leave any chips or burrs on the work2. The method does not leave any chips or burrs on the workpiece.C tti f i t ll d li t d fi3. Cutting forces are virtually zero, so very delicate and finework can be done.Th di i bili d f fi i h4. The process dimension repeatability and surface finishobtained in finishing are extremely good.h h f b d h h d f5. The characteristic surface obtained, which is made up of

craters, helps in better oil retention. This improves die life.6. Because the forces between the tool and the workpiece and

virtually zero, very delicate work can be done.

Di dDisadvantagesO l l t i ll d ti t i l b hi d1. Only electrically conductive materials can be machinedby EDM. Thus non ‐metallic, such as plastics, ceramics

l t b hi d b EDMor glass, cannot be machined by EDM.2. Electrode wear and over‐cut are serious problems.3. A re‐hardened, highly stressed zone is produced on the

work surface by the heat generated during machining.y g g gThis brittle layer can cause serious problems when thepart is put into service.pa t s put to se v ce.

4. Perfectly square corners cannot be made by EDM.Hi h ifi ti ( b t ti th t5. High specific energy consumption (about 50 times thatin conventional machining)

6. MRR is quite low

lApplicationsEDM can be used for machining any material that is

l ll d h l d l ll delectrically conductive, thus including metals, alloys and

most carbidesmost carbides.

EDM is widely used for machining burr free intricateEDM is widely used for machining burr free intricate

shapes, narrow slots and blind cavities etc., for example,p , , p ,

sinking of dies for moulding, die casting, plastic

moulding, wire drawing, compacting, cold heading,

forging, extrusion and press tools.For-2013 (IES, GATE & PSUs) Page 6

ApplicationsEDM is particularly useful when dealing with internal

h h d l h dcuts that are hard to get tools into. Machining tends to

work best with external cutswork best with external cuts.

Almost any geometry (negative of tool geometry) can beAlmost any geometry (negative of tool geometry) can be

generated on a workpiece if a suitable tool can beg p

fabricated (the use of punch as a tool to machine its own

mating die is commonly employed in EDM method).

lApplicationsThe method is also employed for blanking parts from sheets,

cutting off rods of materials flat or form grinding andcutting off rods of materials, flat or form grinding and

sharpening of tools, cutters and broaches.

In EDM method, small holes, about 0.13 mm, in

diameter and as deep as 20mm diameters can be drilled

with virtually no bending or drifting of hole Due to thiswith virtually no bending or drifting of hole. Due to this,

EDM is particularly useful for machining of small holes,

orifices or slots in diesel‐fuel injection nozzles, or in aircraft

engines, air brake valves and so on.

Wire EDMWire EDM is a special form of EDM wherein the

l t d i ti l i d ti ielectrode is a continuously moving conductive wire.

A thin wire of brass tungsten or copper is used as anA thin wire of brass, tungsten, or copper is used as an

electrode.electrode.

The electrode wire is typically made with a 0.05 to 0.25‐yp y 5 5

mm diameter, which is wire electrode wound between

the two spools.

Deionized water is used as the dielectric.

Wire EDMThis process is much faster than electrode EDM.

This process is widely used for the manufacture of

h di d i l i h dpunches, dies, and stripper plates, with modern

machines capable of cutting die relief intricatemachines capable of cutting die relief, intricate

openings, tight radius contours, and corners routinely.p g , g , yGeometrically accurate but moderately finished straighttoothed metallic spur gears, both external and internalp g ,type, can be produced by wire type Electro dischargeMachining (EDM)Machining (EDM).

l h d ( )Electric Discharge Grinding (EDG)EDG i i il EDM h h l d iEDG is similar to EDM except that the electrode is arotating wheel (usually graphite).Positively charged work pieces are immersed in orflooded by a dielectric fluid and fed past the negativelyflooded by a dielectric fluid and fed past the negativelycharged wheel by servo‐controlled machine table.

l d b h h fMetal is removed by intermittent high frequencyelectrical discharges passing through the gap betweenwheel and workpiece.Each spark discharge melts or vaporizes a small amountEach spark discharge melts or vaporizes a small amountof metal from the workpiece surface, producing a small

t t th di h it i EDMcrate at the discharge sit, as in EDM.Fig- Electric Discharge Grinding (EDG)

l h d ( )Electric Discharge Grinding (EDG)Th k i ll h ld 6The spark gap is normally held at 0.013 to 0.076 mmThe graphite wheel is rotated at 0.5 to 3 m/sg p 5 3 /Themethod can be used forE l li d i l i di i l i di d1. External cylindrical grinding, internal grinding andsurface grinding.

2. Grinding carbide and steel at the same time withoutwheel loadingwheel loading.

3. Grinding thin sections where abrasive wheel pressuresh dmight cause distortion.

4. Grinding brittle materials or fragile parts where4. Grinding brittle materials or fragile parts whereabrasive materials might cause fracturing.


Ultrasonic Machiningg

By S K Mondaly

l hUltrasonic Machining l hUltrasonic MachiningI l i hi i l f d i d h ibIn ultrasonic machining, a tool of desired shape vibrates at anultrasonic frequency (19 ~ 25 kHz) with an amplitude of

d h karound 15 – 50 μmover the workpiece.Generally the tool is pressed downward with a feed force, F.y p ,Between the tool and workpiece, the machining zone isflooded with hard abrasive particles generally in the form ofp g ywater based slurry.As the tool vibrates over the workpiece the abrasive particlesAs the tool vibrates over the workpiece, the abrasive particlesact as the indenters and indent both the work material andthe tool The abrasive particles as they indent the workthe tool. The abrasive particles, as they indent, the workmaterial, would remove the same, particularly if the workmaterial is brittle due to crack initiation propagation andmaterial is brittle, due to crack initiation, propagation andbrittle fracture of the material.

l hUltrasonic MachiningUSM i i l d f hi i b i l i lUSM is mainly used for machining brittle materials{which are poor conductors of electricity and thuscannot be processed by Electrochemical and Electro‐discharge machining (ECM and EDM)}.g g ( )}

l hUltrasonic MachiningA f ll i d i h i d i d h i h kAt full indentation, the indentation depth in the workmaterial is characterized by δw. Due to the indentation,as the work material is brittle, brittle fracture takes placeleading to hemi‐spherical fracture of diameter ‘2x’ underg pthe contact zone.If at an moment of time there are an a erage ‘n’ of gritsIf at any moment of time, there are an average n of gritsand the tool is vibrating at a frequency ‘f ’ then material

l b dremoval rate can be expressed as

2MRRw

3/22 ( )3 w bd nfπ δ=3

Process Parameters

Effect of machining parameters on MRR

A lit d f ib ti ( )

Feed force (F)

Amplitude of vibration (ao)

average grit diameter, dg

Frequency of vibration (f)

g g g

q y ( )

Volume concentration of abrasivein water slurry – C

l hUltrasonic Machine l hUltrasonic MachineTh b i h i l f USM i i ilThe basic mechanical structure of an USM is very similarto a drill press.It has additional features to carry out USM of brittlework materialwork material.The workpiece is mounted on a vice, which can bel d h d d d h llocated at the desired position under the tool using a 2axis table.The table can further be lowered or raised toaccommodate work of different thicknessaccommodate work of different thickness.Slurry delivery and return system


l hUltrasonic MachineF d h i id d d f d fFeed mechanism to provide a downward feed force onthe tool during machiningThe transducer, which generates the ultrasonic vibrationThe horn or concentrator which mechanically amplifiesThe horn or concentrator, which mechanically amplifiesthe vibration to the required amplitude of 15 – 50 μm and

d h laccommodates the tool at its tip.

Subsystems of Subsystems of USMUSM

BB

CCAA

EE DDEE

dTransducerTh l i ib i d d b hThe ultrasonic vibrations are produced by thetransducer. The transducer is driven by suitable signalgenerator followed by power amplifier. The transducerfor USM works on the following principleg p p

Piezoelectric effectffMagnetostrictive effect

Electrostrictive effectect ost ct ve e ectMagnetostrictive transducers are most popular andb t t llrobust amongst all.

l h ldTool holder or HornIts function is to increase the tool vibration amplitude

d h h b h l dand to match the vibrator to the acoustic load.

I b d f i l i h d iIt must be constructed of a material with good acoustic

properties and be highly resistant to fatigue crackingproperties and be highly resistant to fatigue cracking.

Monel and titanium have good acoustic properties andMonel and titanium have good acoustic properties and

are often used together with stainless steel, which isg

cheaper.

lToolTools should be constructed from relatively ductile

lmaterials.

Th h d h l i l h f i illThe harder the tool material, the faster its wear rate will

bebe.

Li i iLimitationsL MRRLow MRRRather high tool weargLow depth of hole

lApplicationsU d f hi i h d d b i l lli llUsed for machining hard and brittle metallic alloys,semiconductors, glass, ceramics, carbides etc.Used for machining round, square, irregular shapedholes and surface impressionsholes and surface impressions.Machining, wire drawing, punching or small blankingddies.

NNoteTh f ll i i l i ll hi d b USMThe following material is generally machined by USM

(i) Glass( )(ii) Silicon(iii) G i(iii) Germanium

Tool in USM is generally made of Steelg y

Ch i l M hi iChemical MachiningChemicals are used to dissolve material

Masks are used to control attack

Most common use is circuit boards and plates for

i tiprinting.

Cutting speed of 0 0025 0 1 mm/minute very slowCutting speed of 0.0025‐0.1 mm/minute – very slow


Ch i l M hi iChemical Machining Ph Ch i l M hi iPhoto‐Chemical MachiningPCM i i l l i h i lPCM is a material removal process using chemicals(etchants) to produce high precision parts.This process is also known as Photo Etching, ChemicalBlanking and Photo Chemical MillingBlanking and Photo Chemical Milling.Coat both sides of the plate with photoresist.( h l h dh h l h(photoresist is a polymer that adheres to the metal whenexposed to UV light).Spray metal with etchant or dip it in hot acidic solutionto etch all material other than part covered withto etch all material other than part covered withphotoresist (1‐15 min.).Rinse the plate to ensure photoresist and etchantRinse the plate to ensure photoresist and etchantremoval.

Ph Ch i l M hi iPhoto‐Chemical Machining

Laser Beam Machining

85

Laser Beam MachiningDi l b i f f k i iDirect laser beam against surface of workpiece, as in

laser weldinglaser welding

Successive pulses from laser gun vaporize tiny bits ofSuccess ve pu ses o ase gu vapo e t y b ts o

workpiece

Location of laser beam controlled by computer

Workpiece need not be conductive

Cuts are tapered

86Gotta trap overshoot from laser beam

Laser Beam MachiningProduces large remelt zone

Can produce holes as small as 0.0005 mm diameter

Can produce deep holes

Used to produce cooling holes in blades/vanes for jet

enginesengines

87

Electron Beam MachiningWorkpiece placed in vacuum chamber

High‐voltage electron beam directed toward

workpieceworkpiece

Energy of electron beam melts/ vaporizes selectede gy o e ect o bea e ts/ apo es se ected

region of workpiece

Electron beam moved by deflection coils

Similar process to EB welding

88

Electron Beam Machining

89

Plasma Arc CuttingPlasma is a stream of ionized gas

T i l t t hi hTypical temperatures are very high

Same process as plasma welding without filler metalSame process as plasma welding, without filler metal

Torch movement controlled by computery p

Power requirements depend on material being cut,

plus depth of cut

l i d h i h hRecast layer is deeper than with other processes

90For-2013 (IES, GATE & PSUs) Page 10

Water Jet MachiningNarrow jet of water directed, at high pressure and

velocity, against surface of workpiece

J t f t d f f k i th b Jet of water erodes surface of workpiece, thereby

cutting workpieceg p

Computer control to achieve shape

91

Water Jet Machining

92

Abrasive Jet Machining (Dry)Abrasive Jet Machining (Dry)It is similar to sand blasting, except that a very narrow jet ofgas and abrasive particles achieves localized cuttinggas and abrasive particles achieves localized cutting.It removes material through the eroding action of a highl it t f b i l dvelocity stream of abrasive‐laden gas.

The gas is first compressed and mixed with the abrasived i i i h b d d h h lpowder in a mixing chamber and passed through outlet

nozzle.d hComputer is used to position the jet.

Gas Pressure about 7 atmVelocity of jet about 300 m/sJet Diameter 0.12 mm to 1.25 mmAbrasive used: Al2O3 , SiC with particle size 10 to 50 µmTool (nozzle) material – tungsten carbide or sapphire

93

g ppTool (nozzle) Life – about 30 hours

Abrasive Jet Machining

94

Advantages of AJMCan be used in any material, conductive, non‐

conductive, ductile or brittle

d d l ( )Good dimensional accuracy (±0.05 mm)

G d S f fi i h tGood Surface finish – 0.25 to 1.25 µm

Due to cooling action of gas stream no thermal damageDue to cooling action of gas stream no thermal damage

on the work surface

Due to negligible force delicate workpiece can be

machined.

Disadvantages of AJMLow MRR

Possibility of stray cutting

Embedding of abrasive particles in soft workpiece

Dust control needed

Application of AJMCutting and drilling on metal foils and thin

sections of ceramics and glass

h l l hIntricate holes in electronic components such as

resistor paths in insulationresistor paths in insulation

Engraving of characters on toughened glassEngraving of characters on toughened glass

automobile windows

Cleaning, polishing and deburring the surface

Abrasive WJ CuttingUsed to cut much harder materials

Water is not used directly to cut material as in PureWater is not used directly to cut material as in Pure,

instead water is used to accelerate abrasive particles which

do the cutting

8 h ( d ) i i ll d h h80‐mesh garnet (sandpaper) is typically used though 50

and 120‐mesh is also used

Standoff distance between mixing tube and workpart is

typically 0.010‐0.200 – important to keep to a minimum to

keep a good surface finishkeep a good surface finish

Abrasive WJ CuttinggEvolution of mixing tubeEvolution of mixing tubetechnologyStandard Tungsten CarbideStandard Tungsten Carbidelasts 4‐6 hours (not used muchanymore)anymore)Premium Composite Carbidelasts 100‐150 hoursConsumables include water,,abrasive, orifice and mixingtubetube


Ch‐10: Non‐Conventional Machining Operation

Q. No Option Q. No Option1 D 8 D

B A2 B 9 A3 B 10 B3 B 10 B4 D 11 D4 D 11 D5 D 12 A56 B 13 A7 A 14 B

NC, CNC & RoboticsNC, CNC & Robotics


h / ?What is NC/CNC?NC is an acronym for Numerical Control and CNC is an

f l lacronym for Computer Numerical Control.

What is the difference between NC and CNC ?Th diff b NC d CNC i f dThe difference between NC and CNC is one of age andcapability.The earliest NC machines performed limited functionsand movements controlled by punched tape or punchand movements controlled by punched tape or punchcards.

h h l l d h h dAs the technology evolved, the machines were equipedwith increasingly powerful microprocessors (computers)with the addition of these computers, NC machinesbecome CNC machines.become CNC machines.CNC machines have far more capability than their

d tdpredecessor. contd…..

What is the difference between NC and CNC ?

Some of the enhancements that came along with CNC

l d d l binclude: Canned Cycles, Sub Programming, Cutter

Compensation Work coordinates Coordinate systemCompensation, Work coordinates, Coordinate system

rotation, automatic corner rounding, chamfering, and B‐rotation, automatic corner rounding, chamfering, and B

spline interpolation.

h d d d?Where did CNC get started?1940 Jhon Parson developed first machine able to drill

h l f d d hholes at specific coordinates programmed on punch

cardscards.

1951 MIT developed servo‐mechanism1951 MIT developed servo‐mechanism

1952 MIT developed first NC machines for milling1952 MIT developed first NC machines for milling.

1970 First CNC machines came into picture1970 First CNC machines came into picture

Now‐a‐day’s modified 1970’s machines are used.y 97

D ll hi k th CNCDo all machines speak the same CNC languagelanguage

No, while there is fairly standard set of G and M codes,

th i i ti i th i li ti F lthere is some variation in their application. For example

a G0 or G00 command is universally regarded as thea G0 or G00 command is universally regarded as the

command for rapid travel. Some older machines do notp

have a G00 command. On these machines, rapid travel is

commanded by using the F (feed) word address.

h “ l l”What is a “Conversational Control”CNC machine tool builders offer an option what is

k h l l h l lknown as the conversational control. This control lets

the operator/programmer use simple descriptivethe operator/programmer use simple descriptive

language to program the part. The control thenlanguage to program the part. The control then

displayed a graphical representation of the instructions

so the operator/programmer can verify the tool path.

Are CNC machines faster than l hconventional machines?

Yes, No, Sometimes. When it comes to making a single,

simple part it is hard to beat a conventional mill or lathe.

CNC machines move faster in rapid travel than

i l hiconventional machines.


Are CNC machines more accurate h l hthan conventional machines?

Yes, they can be. But like anything else it depends ony y g p

who is running the machine, how well the machines has

been maintained, quality of setup and so on.

NC/CNC Machines‐AdvantagesHigh Repeatability and Precision e.g. Aircraft partsVolume of production is very highVolume of production is very highComplex contours/surfaces need to be machined. E.g.TurbinesFlexibility in job change automatic tool settings lessFlexibility in job change, automatic tool settings, lessscrapM f hi h d i i b liMore safe, higher productivity, better qualityLess paper work, faster prototype production, reductionp p , p yp p ,in lead times

NC/CNC Machines‐DisadvantagesCostly setup, skilled operators

Computers, programming knowledge required

Maintenance is difficult

NC/CNC/DNCDirect Numerical Control is a system that uses acentral computer to control several machines at the sameptimeDistributed Numerical Control (DNC): the centralDistributed Numerical Control (DNC): the centralcomputer downloads complete programs to the CNC

hi hi h b k i PC dmachines, which can be workstations or PCs, and can getthe information for the machine operations.The speed of the system is increased, large files can behandled and the number of machine tools used ishandled and the number of machine tools used isexpanded.

112

Direct numerical controlDirect numerical control

113

DNCDNC

114

Stepper MotorThe stepper motor is special type of synchronous motor

h h d d h h f lwhich is designed to rotate through a specific angle

(Called step) for each electrical pulse received from the(Called step) for each electrical pulse received from the

control unit.control unit.

Basic CNC Principlesph ( )Basic Length Unit (BLU)

I NC hi h di l l h lIn NC machine, the displacement length per one pulseoutput from machine is defined as a Basic Length Unit(BLU).In the CNC computer each bit (binary digit) represents 1In the CNC computer each bit (binary digit) represents 1BLU.

Bit = BLUExample: If one pulse makes a servo motor rotate by onea p e: o e pu se a es a se vo oto otate by o edegree and the servo motor moves the table by 0.0001mm one BLU will be 0 0001 mmmm, one BLU will be 0.0001 mm.The lead of a ball screw is related to the displacementunit of the machine tool table.


Control Systems possible in CNC MachineP i i dPoint to point mode:

Point‐to‐point straight line mode

dCo‐ordinate systemAll h hi l C i C diAll the machine tool use Cartesian Co‐ordinate system.The first axis to be identified is the Z – axis, This is,followed by X and Y axes respectively.

Right‐hand coordinate systems


5 axes CNC vertical axis machining centre configuration

Absolute and Incremental Coordinate System

Absolute Coordinate System Incremental Coordinate System

The following are the steps to be followed while developing the CNC part programswhile developing the CNC part programs.

Process planningp gAxes selectionT l l tiTool selectionCutting process parameters planningg p p p gJob and tool setup planningM hi i th l iMachining path planningPart program writingp g gPart program proving

h l ( ) d dFor a CNC machine control unit (MCU) decides cuttingspeed, feed, depth of cut, tool selection , coolant on offp pand tool paths. The MCU issues commands in form ofnumeric data to motors that position slides and toolnumeric data to motors that position slides and toolaccordingly.

Part ProgrammingFANUC CONTROLL

SIEMENS CONTROLL

CNC iCNC programmingImportant things to know:Important things to know:

• Coordinate SystemCoordinate System

• Units, incremental or absolute positioningUnits, incremental or absolute positioning

• Coordinates: X,Y,Z, RX,RY,RZ, , , , ,

• Feed rate and spindle speedp p

• Coolant Control: On/Off Flood MistCoolant Control: On/Off, Flood, Mist

• Tool Control: Tool and tool parameters• Tool Control: Tool and tool parameters

Programming Key LettersO ‐ Program number (Used for program identification)N ‐ Sequence number (Used for line identification)N Sequence number (Used for line identification)G ‐ Preparatory functionX ‐ X axis designationgY ‐ Y axis designationZ ‐ Z axis designationgR ‐ Radius designationF – Feed rate designationS ‐ Spindle speed designationH ‐ Tool length offset designationD ‐ Tool radius offset designationT ‐ Tool DesignationM ‐Miscellaneous function

Table of Important G codespCode Meaning FormatG00 Rapid Transverse N__G00 X___ Y___ Z___G01 Linear Interpolation N__G01 X___ Y___ Z___ F___pG02 Circular Interpolation,

CWN__G02 X__ Y__ Z___ R___ F___

N G X Y Z I J K F CW N__G02 X___ Y__Z__I ___J __K __ F __

G03 Circular Interpolation,CCW

N__G03 X___ Y___ Z__R__F___

CCW N__G03 X__ Y__Z__I __J __K __ F __

G04 Dwell N__G04P___G04 DwellG17 XY PlaneG 8 XZ PlG18 XZ PlaneG19 YZ Plane


Table of Important G codespCode Meaning FormatG20/G70 Inch UnitG21/G71 Metric Unit7G28 Automatic Return to Reference

PointPointG40 Cutter compensation cancelG C tt ti l ft N G DG41 Cutter compensation left N__G41D__G42 Cutter compensation right N__G42D__

G43 Tool length compensation N__G43H__(plus)

Table of Important G codespCode Meaning FormatG44 Tool length compensation

(minus)N__G44H__

G49 Tool length compensation cancel

G80 Cancel canned cyclesG81 Drilling cycle N G81 Z R FG81 Drilling cycle N__G81 Z__R__F__

G90 Absolute positioningG91 Incremental positioningG92 Absolute preset, change the N__G92X__Y__Z__

datum position

Rapid traverse: G00pG00: G00:

to make the machine move at maximum speed. It is used for positioning motion It is used for positioning motion.

G90 G00 X20.0 Y10.0

EndG90:

absolute (20,10)absolute coordinates (10,10)

Start (0,0)

Linear interpolation: G01 pG01:

linear interpolation at feed speed.G91 G0l X200.0 Y100.0 F200.0

YEndG91:

100.0 End9incremental coordinates

XStart 200.0

Circular interpolation: G02, G03Circular interpolation: G02, G03 G02, G03:

For circular interpolation the tool destination and the circle For circular interpolation, the tool destination and the circle center are programmed in one block G02 is clockwise interpolation, G03 is counterclockwise i l iinterpolation

;02

17 FR

YXG

G ⎬⎫

⎨⎧

⎬⎫

⎨⎧

;02

18

__;____

____03

17

FR

ZXG

G

FJI

YXG

G

⎬⎫

⎨⎧

⎬⎫

⎨⎧

⎭⎬

⎩⎨

⎭⎬

⎩⎨

;02

19

__;____

____03

18

FR

ZYG

G

FKI

ZXG

G

⎬⎫

⎨⎧

⎬⎫

⎨⎧

⎭⎬

⎩⎨

⎭⎬

⎩⎨

__;____

____03

19 FKJ

ZYG

G⎭⎬

⎩⎨

⎭⎬

⎩⎨

End Circle center, radiuspoint

,

Circular interpolation: G02, G03Circular interpolation: G02, G03Y

EndR=-50mm

Y

XS if R i h End Specify R with sign before it:

Start R=50mm

≤180° +R

>180° ‐RStart

G91 G02 X60.0 Y20.0 R50.0 F300.0G91 G02 X60.0 Y20.0 R‐50.0 F300.0

Circular interpolation: G02 G03Circular interpolation: G02, G03Specify Center with I, J, K

I, J, K are the incremental

Y EndJ

distance from the start of the arc;X

Viewing the start of arc as the origin, I, J, K have

i i i i

Startpositive or negative signs.

Center

i

j

i

Circular interpolation: G02, G03Circular interpolation: G02, G03N0010 G92 X200.0 Y40.0 Z0 ;N0020 G90 G03 X140.0 Y100.0 I ‐60.0 F300；N0030 G02 X120. 0 Y60.0 I‐ 50.0；

OrG92:

T d fi ki OrN0010 G92 X200.0 Y40.0 Z0；N0020 G90 G03 X140.0 Y100.0 R60.0 F300；

To define working coordinate

N0020 G90 G03 X140.0 Y100.0 R60.0 F300；N0030 G02 X120.0 Y60.0 R50.0；

YG

R60R50100

60

YG90: absolute

coordinates

90 120 140 200

6040

OX

90 120 140 200O

Circular interpolation: G02 G03Circular interpolation: G02, G03

Annotation for Circular InterpolationpI0.0, J0.0, and K0.0 can be omitted. If X YZ are all omitted in the program that means If X,Y,Z are all omitted in the program, that means start and end of arc are same points.

N0020 G02 I20 0 (a full circle)N0020 G02 I20.0 (a full circle)If I, J, K, and R all appears in circular interpolation i t ti R i lid d I J d K i lidinstruction, R is valid and I, J, and K are invalid


Tool CompensationpTool‐Radius Compensation oo Rad us Co pe sat o

Left hand G41 Right hand G42 Right hand G42 Cancel tool‐radius compensation G40

Tool‐Height CompensationPositive G43 os e G43Negative G44 Cancel tool height compensation G49Cancel tool‐height compensation G49

Tool‐Radius CompensationpTool‐radius compensations make it possible to program directly from the drawing and thus eliminate program directly from the drawing, and thus eliminate the tool‐offset calculation

G (G ) DG41 (G42) D××D××: the radius of tool to compensate is saved in a memory unit that is named D××G41/G42 is directly related with direction of tool movement and which side of part is cut.

Cancel Tool Compensation: G40p

Note the difference between two waysNote the difference between two ways

N0060 G01 X2 000 Y1 700N0060 G40 G01 X2.000 Y1.700 M02

N0060 G01 X2.000 Y1.700N0070 G40 M02

ramp off block effective to the end point

Tool‐Height Compensationg pG43 (G44) H××G43 (G44) H××

H××: specified memory unit used to save height H××: specified memory unit used to save height compensation of tool.Positive compensation (G43): Positive compensation (G43): real position = specified position + value saved in H××Negative compensation (G44): real position = specified position ‐ value saved in H××p p p

Tool‐Height CompensationTool‐Height CompensationExample:Example:

N0010 G91 G00 X12.0 Y80.0 N G Z H

G91: i t l N0020 G44 Z‐32.0 H02； incremental coordinates

If we put 0.5mm into H02, real position = ‐32.0 ‐ 0.5 = ‐32.5p 3 5 3 5

Cancel tool‐height compensation: G49Cancel tool‐height compensation: G49

Table of Important M codesM00 Program stopM01 Optional program stopM01 Optional program stopM03 Spindle on clockwiseM S i dl t l k iM04 Spindle on counterclockwiseM05 Spindle stopM06 Tool changeM08 Coolant onM09 Coolant offM10 Clamps onM10 Clamps onM11 Clamps offM M P M02 or M30 Program stop, reset to start

R l f iRules for programmingBlock Format

N135 G01 X1.0 Y1.0 Z0.125 F5

Sample Block• Restrictions on CNC blocks• Each may contain only one tool movey y• Each may contain any number of non-tool move G-codes• Each may contain only one feed rate• Each may contain only one specified tool or spindle speed• Each may contain only one specified tool or spindle speed• The block numbers should be sequential• Both the program start flag and the program number must beindependent of all other commands (on separate lines)independent of all other commands (on separate lines)• The data within a block should follow the sequence shownin the above sample block

E l f CNC P iExample of CNC Programming

What Must Be Done To Drill A Hole On A CNC Vertical Milling Machine

Top O0001Top View N005 G54 G90 S600 M03

N G X YN010 G00 X1.0 Y1.0N015 G43 H01 Z.1 M085 43N020 G01 Z‐.75 F3.5N025 G00 Z 1 M09

Front N030 G91 G28 X0 Y0 Z0N025 G00 Z.1 M09

View N035 M30M30 End of Program3 g


APT LanguageAPT (A i ll P d T l )APT (Automatically Programmed Tools)The APT language consists of many different types ofstatements made up of the following valid letters, numeralsand punctuation marks.pLetters: ABCDEFGHIJKLMNOPQRSTUVWXYZNumerals: 0 1 2 3 4 5 6 7 8 9Numerals: 0 1 2 3 4 5 6 7 8 9/ A slash divides a statement into two sections. eg.,

GO/PAST, , A comma is used as a separator between the elements in , p

a statement generally to the right of the slash.= An equals is used for assigning an entity to a symbolic = An equals is used for assigning an entity to a symbolic

name, e.g., P1 = POINT/25,50,30.

W dWordsThe words to be used in the statements are built up from

l l h h f bone to six letters or numerals with the first one being a

letter No special character is allowed in the wordsletter. No special character is allowed in the words.

The complete APT part program consists of the following four types of statementsthe following four types of statements

GeometryGeometry

Motion Motion

Post processorPost processor

Compilation controlCompilation control

Other Part Programming LanguagesADAPT (AD i APT) h fi d APTADAPT (ADaptation APT) was the first attempt to adapt APTprogramming system for smaller computersAUTOSPOT (AUTO ti S t f PO iti i T l )AUTOSPOT (AUTOmatic Sytem for POsitioning Tools) wasdeveloped by IBM and first introduced in 1962EXAPT (EXtended subset of APT) was developed jointly inEXAPT (EXtended subset of APT) was developed jointly inGerman in about 1964 by several universities to adapt APT forEuropean use. It is compatible with APT and thus can use thep psame processor as APTCOMPACT was developed by Manufacturing Data Systems, Inc.( )

p y g y(MDSI)SPLIT (Sundstrand Processing Language Internally Translated)

d l d b S d d C i i d d f iwas developed by Sundstrand Corporation, intended for its ownmachine toolsMAPT (Mi APT) i b t f APT t b thMAPT (Micro‐APT) is a subset of APT, to be run on themicrocomputers

158

APT LanguageAPT LanguageAdditional statements:MACHIN/DRILL, 2COOLNT/

For example: COOLNT/MIST COOLNT/FLOOD COOLNT/OFFFEDRAT/SPINDL/

For example: SPINDL/ON SPINDL/1250, CCLWTOOLNO/TURRET/END

159

Point (POINT)Point (POINT)

PTA = POINT/ 3,4,5

y

(3, 4, 5)

PTA

z

x

Point (POINT)( )

PTB = POINT/ INTOF, LIN1, LIN2

LIN2

LIN1PTB

Point (POINT)( )

PTD = POINT/ YSMALL, INTOF, LIN3, C1PTD = POINT/ XSMALL, INTOF, LIN3, C1

yPTD POINT/ XSMALL, INTOF, LIN3, C1PTC = POINT/ YLARGE, INTOF, LIN3, C1PTC = POINT/ XLARGE, INTOF, LIN3, C1 PTC

LIN3

PTD

C1

PTD

x


Point (POINT)( )

PTE = POINT/ YLARGE, INTOF, C1, C2PTE = POINT/ XLARGE, INTOF, C1, C2 yPTF = POINT/ YSMALL, INTOF, C1, C2PTF = POINT/ XSMALL, INTOF, C1, C2 C1

PTE

C2PTF

x

Point (POINT)Point (POINT)

PT7 = POINT/ CENTER, C6

y

C6

PT7

x

Line (LINE)Line (LINE)

LIN1 = LINE/ P1, P2

y

P2

y

P1P1

LIN1

xx

Line (LINE)Line (LINE)

LIN4 = LINE/ PT6, 15, -30, 3

y

PT6

L4 (15, ‐30, 3)

xx

Line (LINE)( )

L12 = LINE/ PT4, ATANGL, 20, XAXISL14 = LINE/ PT1, ATANGL, 40L15 = LINE/ 32, -3, 2, ATANGL, -15, XAXISL16 = LINE/ PT3, ATANGL, 40, YAXIS

yPT3 L14

L16PT1 L12

PT4

40°

PT4

x

40° 20°

15° x(32, ‐3, 2)

L1515°

Line (LINE)( )

LIN = LINE/ POINT ATANGL ANGLE (in degrees) LINELIN = LINE/ POINT, ATANGL, ANGLE (in degrees), LINE

LINE2

y

P1

LINE130°

LINE2 = LINE/ P1, ATANGL, 30, LINE1

x

3

Line (LINE)( )

LIN = LINE/ SLOPE SLOPE VALUE INTERC MODIFIER dLIN LINE/ SLOPE, SLOPE VALUE, INTERC, MODIFIER, dwhere the slope value is y/x. The modifier options are [XAXIS,

YAXIS] and d is the corresponding intercept value on the selectedYAXIS], and d is the corresponding intercept value on the selectedaxis (i.e., modifier).

y

LINE1

LINE1 = LINE/ SLOPE, 1, INTERC, XAXIS, 6

x(6,0) Point of X‐Intercept(6,0) Point of X Intercept

Line (LINE)( )

LIN LINE/ ATANGL DEGREES INTERC MODIFIER dLIN = LINE/ ATANGL, DEGREES, INTERC, MODIFIER, dThe modifier options are [XAXIS, YAXIS], and d is the

corresponding intercept value on the selected axis (i.e., modifier).

y

LINE1LINE1

LINE1 = LINE/ ATANGL, 30, INTERC, d

xd

θ = 30°

d

Line (LINE)( )

The LEFT & RIGHT modifier indicates whether the lineis at the left or right tangent point, depending on howg g p , p gone looks at the circle from the point.

L1 = LINE/ PT51, LEFT, TANTO, C11

L1

C11

PT51


Line (LINE)( )

L2 = LINE/ PT51 RIGHT TANTO C11L2 = LINE/ PT51, RIGHT, TANTO, C11L3 = LINE/ PT40, RIGHT, TANTO, C11L4 = LINE/ PT40, LEFT, TANTO, C11

L3 RightL3 Right

PT40L1

Left

PT40

Left L4

Right

PT51

L2L2

Line (LINE)( )L6 = LINE/ LEFT, TANTO, C3, LEFT, TANTO, C4

L6

C3

C4Left

C3Right

L9L8

L7L7

The descriptive words LEFT and RIGHT are used byThe descriptive words LEFT and RIGHT are used bylooking from the first circle written towards the

d i lsecond circle.

Line (LINE)( )

L6 = LINE/ RIGHT, TANTO, C4, RIGHT, TANTO, C3

L6

C4Right

C3

C4

Left

L9L8

L7

Line (LINE)( )

LN3 = LINE/ PNT6, PARLEL, LN15LN4 LINE/ PNT5 PERPTO LN13LN4 = LINE/ PNT5, PERPTO, LN13

y

PNT6 LN3 PNT5LN3

LN4

LN15LN13LN13

x

Line

LN5 = LINE/ INTOF, PLAN1, PLAN2

LN5

PLAN1

PLAN2

Plane (PLANE)( )

PLAN10 = PLANE/ PT6, PT12, PT15

PLAN10PT15

PT12PT6

PLAN10

PT12PT6

y 3.0

PT4PT4z

PLAN14

x

Plane (PLANE)( )

PLAN14 = PLANE/ PT4, PARLEL, PLAN10PLAN14 = PLANE/ PARLEL PLAN10 YSMALL 3 0PLAN14 = PLANE/ PARLEL, PLAN10, YSMALL, 3.0

PT15

PLAN10

PT12PT6y

3.0

PT44

zPLAN14

x

4

Circle (CIRCLE)Circle (CIRCLE)

C1 = CIRCLE/ 3, 6, 5, 4.3C1 CIRCLE/ 3, 6, 5, 4.3C1 = CIRCLE/ CENTER, PT3, RADIUS, 4.3

C1

y

C1

4.3

PT3(3,6,5)(3,6,5)

x

Circle (CIRCLE)Circle (CIRCLE)

C3 = CIRCLE/ CENTER, PT6, TANTO, LN4C7 = CIRCLE/ CENTER, PT8, PT5

y

LN4

y

LN4PT5

C3PT6

C7PT8

C3 C7

x x


The Machining PlanThe Machining Plan

Contouring:

Part surface: the surface on which the end of thetool is ridingtool is riding.

Drive surface: the surface against which the edge ofg gthe tool rides.

Check surface: a surface at which the current toolmotion is to stop.motion is to stop.


z

y

Drive surface Check surface

cutterDirection of cutter motion

x

Part surface

The Machining Plang

CS CS CS

DS DS DS

TO ON PASTTO ON PAST


Motion commands:

GOLFT/ : Move left along the drive surface

GORGT/ : Move right along the drive surfaceGORGT/ : Move right along the drive surface

GOUP/ : Move up along the drive surfacep g

GODOWN/ : Move down along the drive surface

GOFWD/ : Move forward from a tangent position

GOBACK/ M b k d f t t itiGOBACK/ : Move backward from a tangent position

GOUP

GOFWDGOLFT

GOFWD

Present toolpositionGOBACK

GORGT

p

GODOWN

Previoustool position

FROM/PTARGFROM/PTARGGO/TO, L1, TO, PL2, TO L3GORGT/L3, PAST, L4

Machining Specifications

Postprocessor commands for a particular machine tool are:

MACHIN/ d t if th hi t l d ll thMACHIN/ : used to specify the machine tool and call thepostprocessor for that tool:

MACHIN/ DRILL, 3

COOLNT/ : allows the coolant fluid to be turned on or off:COOLNT/ : allows the coolant fluid to be turned on or off:

COOLNT/ MIST

COOLNT/ FLOOD

COOLNT/ OFFCOOLNT/ OFF


FEDRAT/ : specifies the feed rate for moving the tool along thef i i h ipart surface in inches per minute:

FEDRAT/ 4.5

SPINDL/ : gives the spindle rotation speed in revolutions periminute:

SPINDL/ 850

TURRET/ : can be used to call a specific tool from an automatict l htool changer:

TURRET/ 11

Machining SpecificationsTOLERANCE SETTING: Nonlinear motion is accomplished in

straight-line segments and INTOL/ and OUTTOL/ statementsstraight line segments, and INTOL/ and OUTTOL/ statementsdictate the number of straight-line segments to be generated.

INTOL/ 0.0015

OUTTOL/ 0.001


Machining SpecificationsPARTNO: identifies the part program and is inserted at the start of

the programthe program.

CLPRNT: indicates that a cutter location printout is desired.

CUTTER: specifies a cutter diameter for offset (rough versus finishcutting). If a milling cutter is 0.5 in. in diameter and we haveg) g

CUTTER/ 0.6

then the tool will be offset from the finish cut by 0.05 in.


FINI: specifies the end of the program.APT LanguageAPT Language

Other Motion statements:GO/{TO}, Drive surface, {TO} Part surface, {TO}, Check surface

OrGO/{TO}, Drive surface, {TO} Part surface, {TANTO}, Check surface

…And the same with PAST or ON instead of TOGOLFT/GORGT/GOUP/GOUP/GODOWN/GOFWD/GOBACK/GOBACK/For example:

GO/TO, L1, TO, PS, TANTO, C1GO/PAST L1 TO PS TANTO C1GO/PAST, L1, TO, PS, TANTO, C1

192

IES‐2008Name the four types of statements in a complete APTpart program. Prepare part program for geometrydescription of the contour shown in the figure below:p g

[15‐Marks]30 40

Y

R 20L3L2

20C1

R 2135°

3

L180L4

R 20L5

C2

P1R20

P1P2X

IES‐2007Prepare part using APT language formilling the contourshown in Fig. in a single pass. [20‐Marks]

110R30

DCR30

QB

110

++

120

E ++

40R40

++ 40100A F

PMaterial : M S.

8 mm

Answer:Answer:PARTNO CONTOURMACHIN/MILL, 2CLPRNTUNITS/MMP0 = POINT/0.0, 0.0, 10.0P0 POINT/0.0, 0.0, 10.0PTA = POINT/0.0, 0.0, 0.0PTB = POINT/0.0, 120.0, 0.0PTC = POINT/30 0 150 0 0 0PTC = POINT/30.0, 150.0, 0.0PTD = POINT/140.0, 150.0, 0.0PTE = POINT/140.0, 40.0, 0.0PTF = POINT/100.0, 0.0, 0.0PTQ = POINT/30.0, 120.0, 0.0PTP = POINT/140.0, 0.0, 0.0PTP POINT/140.0, 0.0, 0.0LAB = LINE/PTA, PTBLCD = LINE/PTC, PTDLDE = LINE/PTD PTELDE = LINE/PTD, PTELAF = LINE/PTA, PTFCBC = CIRCLE/CENTRE, PTQ, RADIUS, 30.0CEF = CIRCLE/CENTRE, PTP, RADIUS, 40.0PL1=PLANE/PTA, PTB, PTC

Contd….

CUTTER/25.0TOLER/0.1INTOL/0.05OUTTOL/0.05FEDRAT/200FEDRAT/200SPINDL/500, CLWCOOLNT/ONCOOLNT/ONFROM/P0GO/TO, LAB, TO, PL1, TO, LAFGOLFT/LAB, TANTO, CBCGOFWD/CBC, PAST, LCDGORGT/LCD PAST LDEGORGT/LCD, PAST, LDEGORGT/LDE, PAST, CEFGORGT/CEF PAST LAFGORGT/CEF, PAST, LAFGORGT/LAF, PAST, LAB

Contd….

RAPIDGOTO/P0COOLNT/OFFSPINDL/OFFENDENDFINI

IES‐2006Prepare part program to machine the contour shown inthe figure using APT on CNCmilling machine.

[15‐Marks]R30 5

•

•

R20

R30

•

80

100 mm

200 60 50

200 mm

Material: MS Thickness: 8.0 mmFor-2013 (IES, GATE & PSUs) Page 22

Home WorkWrite a complete part program in APT for machiningWrite a complete part program in APT for machiningthe product which is given in the diagram. Thickness ofth k i i 6 All di i ithe workpiece is 6 mm. All dimensions are in mm.

[15]

PARTNO CONTOURMACHIN/MILL, 1/ ,CLPRNTUNITS/MMUNITS/MMP0 = POINT/‐25.0,‐25.0, 25.0P1 = POINT/0.0, 0.0, 6.0P2 = POINT/117 0 32 0 6 0P2 = POINT/117.0, 32.0, 6.0P3 = POINT/117.0, ‐32.0, 6.0C1=CIRCLE/CENTER, P1, RADIUS, 10.0C2=CIRCLE/CENTER, P2, RADIUS, 12.5/ , , , 5C3=CIRCLE/CENTER, P3, RADIUS, 12.5

L1 = LINE/RIGHT, TANTO, C1, RIGHT, TANTO, C3L2 = LINE/LEFT, TANTO, C1, LEFT, TANTO, C2C4=CIRCLE/XLARGE, OUT, C2, OUT, C3, RADIUS, 62PL1=PLANE/P1, P2, P3PL1 PLANE/P1, P2, P3REMARK POSTPROCESSOR STATEMENT FOLLOWCUTTER/50 0CUTTER/50.0TOLER/0.01INTOL/0.05OUTTOL/0.05FEDRAT/200SPINDL/1000, CLWSPINDL/1000, CLWCOOLNT/ON

REMARK MOTION STATEMENT FOLLOWFROM/P0FROM/P0GO/TO, L1, TO, PL1, TANTO, C1GORGT/L TANTO CGORGT/L1, TANTO, C3GOFWD/C3, TANTO, C4GOFWD/C4, TANTO, C2GOFWD/C2, PAST, L2GOFWD/C2, PAST, L2GOFWD/L2, TANTO, C1GOFWD/C PAST LGOFWD/C1, PAST, L1RAPIDGOTO/P0COOLNT/OFFCOOLNT/OFFSPINDL/OFFENDENDFINI

RoboticsRoboticsWhat is an industrial robot?

A robot is a reprogrammable, multifunctionalmanipulator designed to handle material, parts, tools orp g , p ,specialized devices through variable programmedmotions for the performance of a variety of tasksmotions for the performance of a variety of tasks.

Ad t f R b tAdvantages of RobotsRobotics and automation can, in many situation, increase

d i i f ffi i li d i fproductivity, safety, efficiency, quality, and consistency ofproductsRobots can work in hazardous environmentsRobots can work in hazardous environmentsRobots need no environmental comfortRobots work continuously without any humanity needs andRobots work continuously without any humanity needs andillnessesRobots have repetable precision at all timesp pRobots can be much more accurate than humans, they may havemili or micro inch accuracy.R b d h i h bili i b d h fRobots and their sensors can have capabilities beyond that ofhumansRobots can process multiple stimuli or tasks simultaneouslyRobots can process multiple stimuli or tasks simultaneously,humans can only one.Robots replace human workers who can create economicRobots ep ace u a o e s o ca c eate eco o cproblems

Di d t f R b tDisadvantages of RobotsRobots lack capability to respond in emergencies, this can cause:

d– Inappropriate and wrong responses– A lack of decision‐making power– A loss of powerA loss of power– Damage to the robot and other devices– Human injuriesb h l d b lRobots may have limited capabilities in

– Degrees of Freedom– Dexterity– Dexterity– Sensors– Vision systems– Real‐time ResponseRobots are costly, due to

Initial cost of equipment– Initial cost of equipment– Installation Costs– Need for peripherals– Need for training– Need for Programming

What Can Robots Do?

Industrial Robots

•Material handling•Material transfer

Material Handling

•Machine loading and/or unloading•Spot weldingC ti ldi Material Handling

Manipulator•Continuous arc welding•Spray coating•AssemblyAssembly•Inspection

Assembly Assembly Manipulator

Spot Welding ManipulatorFor-2013 (IES, GATE & PSUs) Page 23

A i ' h l f b iAsimov's three laws of roboticsFirst law (Human safety):A robot may not injure a human being or throughA robot may not injure a human being, or, throughinaction, allow a human being to come to harm.

S d l (R b l )Second law (Robots are slaves):A robot must obey orders given it by human beings,y g y g ,except where such orders would conflict with the FirstLawLaw.

Third law (Robot survival):A robot must protect its own existence as long as suchprotection does not conflict with the First or Secondprotection does not conflict with the First or SecondLaw.

ll b h h f ll bAll robots have the following basic components:1. Manipulators: the mechanical unit, often called the1. Manipulators: the mechanical unit, often called the

"arm," that does the actual work of the robot. It iscomposed of mechanical linkages and joints with actuatorsp g jto drive the mechanism directly or indirectly through gears,chains, or ball screws.

2. Feedback devices: transducers that sense the positions ofvarious linkages and joints and transmit this information tog jthe controllers in either digital or analog Form.

3. End effectors: the "hand" or "gripper" portion of the3 g pp probot, which attaches the end of the arm and perform theoperations of the robot.p

4. Controller: the brains of the system that direct themovements of the manipulator.p

5. Power supply

Wrist Configurations

Wrist assembly is attached to end‐of‐armWrist assembly is attached to end of armEnd effector is attached to wrist assembly F i f i bl i i d ffFunction of wrist assembly is to orient end effector

Body‐and‐arm determines global position of end effector

Two or three degrees of freedom:gRoll PitchPitchYaw

E d EffEnd EffectorsThe special tooling for a robot that enables it to perform a specific taskTwo types:

Grippers – to grasp and manipulate objects (e g Grippers – to grasp and manipulate objects (e.g., parts) during work cycleTools to perform a process e g spot welding spray Tools – to perform a process, e.g., spot welding, spray painting

Grippers and ToolsGrippers and ToolsDegrees of FreedomDegrees of Freedom

The degree of freedom or grip of a robotic system can beThe degree of freedom or grip of a robotic system can be

compared to the way in which the human body moves.

For each degree of freedom a joint is required.

The degrees of freedom located in the arm define the

fi ticonfiguration.

Each of the five basic motion configurations utilizes threeEach of the five basic motion configurations utilizes three

degrees of freedom in the arm.

Three degrees of freedom located in the wrist give the end

effector all the flexibility.

D f F d ( td )Degrees of Freedom (contd.)

A total of six degrees of freedom is needed to locate arobot’s hand at any point in its work space.Although six degrees of freedom are needed forg gmaximum flexibility, most robot employee only three tofive degrees of freedom.gThe more the degrees of freedom, the greater is thecomplexity of motions encounteredcomplexity of motions encountered.The three degrees of freedom located in the arm of

b ia robotic system are:The rotational reverse: is the movement of the arme otat o a eve se: s t e ove e t o t e aassembly about a rotary axis, such as left‐and‐rightswivel of the robot’s arm about a baseswivel of the robot s arm about a base.

D f F d ( td )Degrees of Freedom (contd.)

The radial traverse: is the extension and retractionof the arm or the in‐and‐out motion relative to thebase.base.The vertical traverse: provides the up‐and‐down

ti f th f th b ti tmotion of the arm of the robotic system.The three degrees of freedom located in the wrist,which bear the names of aeronautical terms, are

Pitch or bend: is the up‐and‐down movement of thePitch or bend: is the up and down movement of thewrist.Y i h i h d l f f h iYaw: is the right‐and‐left movement of the wrist.Roll or swivel: is the rotation of the hand.


Types of RobotC t i G tCartesian or Gantryrobot:I ' b hIt's a robot whose armhas three prismaticjoints whose axes arejoints, whose axes arecoincident with aCartesian coordinatorCartesian coordinator.Used for pick and placework application ofwork, application ofsealant, assemblyoperations handlingoperations, handlingmachine tools and arcwelding.welding.

Types of RobotC li d i l bCylindrical robot:It's a robot whose axesform a cylindricalcoordinate systemcoordinate system.Used for assembly

h dloperations, handling atmachine tools, spotwelding, and handlingat die castingat die castingmachines.

Types of RobotS h i lSpherical orPolar robot:It's a robot whose axesform a polar coordinatepsystem.Used for handling atUsed for handling atmachine tools, spotwelding diecastingwelding, diecasting,fettling machines, gaswelding and arcwelding and arcwelding.

Types of RobotTypes of RobotSCARA robotSC R obotThe SCARA acronym standsf S l ti C li t A blfor Selective Compliant AssemblyRobot Arm or Selective CompliantArticulated Robot Arm.It's a robot which has two parallelIt s a robot which has two parallelrotary joints to provide compliancein a planein a planeUsed for pick and place work,application of sealant, assemblyoperations and handling machinep gtools

Types of RobotA i l dArticulated orRevolute Robot:It's a robot whose armhas at least three rotaryhas at least three rotaryjoints.

d f blUsed for assemblyoperations, die casting,fettling machines, gaswelding, arc weldingwelding, arc weldingand spray painting.

Types of RobotP ll l bParallel robotOne use is a mobileplatform handlingcockpit flightcockpit flightsimulators. It's a robothose arms ha ewhose arms have

concurrent prismaticor rotary joints.

Joint Drive SystemsJoint Drive SystemsElectric

Uses electric motors to actuate individual jointsPreferred drive system in today's robotsy y

HydraulicUses hydraulic pistons and rotary vane actuatorsUses hydraulic pistons and rotary vane actuatorsNoted for their high power and lift capacity

PneumaticTypically limited to smaller robots and simple material yp y ptransfer applications

R b t C t l S tRobot Control SystemsLimited sequence control – pick‐and‐place q p poperations using mechanical stops to set positionsPlayback with point to point control records Playback with point‐to‐point control – records work cycle as a sequence of points, then plays back th d i tithe sequence during program executionPlayback with continuous path control –y pgreater memory capacity and/or interpolation capability to execute paths (in addition to points)p y p ( p )Intelligent control – exhibits behavior that makes it seem intelligent e g responds to sensor inputs it seem intelligent, e.g., responds to sensor inputs, makes decisions, communicates with humans

Robot Control SystemRobot Control System

CellSupervisor

Level 2

Controller Level 1& Program

Level 1

Joint 1 Joint 2 Joint 3 Joint 4 Joint 5 Joint 6 Sensors Level 0


W ki E lWorking Envelope R b i A W ldi C llRobotic Arc‐Welding CellRobot performs fl d flux‐cored arc welding (FCAW)

i operation at one workstation hil fi while fitter

changes parts at the other workstation

R b t P iRobot ProgrammingLeadthrough programmingeadt oug p og a g

Work cycle is taught to robot by moving thei l t th h th i d ti l dmanipulator through the required motion cycle and

simultaneously entering the program into controllermemory for later playback

Robot programming languagesRobot programming languagesTextual programming language to enter commandsi t b t t llinto robot controller

Simulation and off‐line programmingp g gProgram is prepared at a remote computer terminaland downloaded to robot controller for executionand downloaded to robot controller for executionwithout need for leadthrough methods

Leadthrough Programming1. Powered leadthrough

C f iCommon for point‐to‐point robotsUses teach pendant

2. Manual leadthroughgConvenient for continuous path continuous path control robotsHuman programmer Human programmer physical moves manipulatormanipulator

Leadthrough Programming AdvantagesAd tAdvantages:

Easily learned by shop personnelLogical way to teach a robotNo computer programmingNo computer programming

Disadvantages:dDowntime during programming

Limited programming logic capability p g g g p yNot compatible with supervisory control

CADComputer Aided Design (CAD): Used for creating the

product database

Geometric Modeling

lEngineering Analysis

D i R i d E l iDesign Review and Evaluation

A t t d D ftiAutomated Drafting

CAMd d f ( )Computer Aided Manufacturing (CAM):

Computer Aided Process Planning (CAPP)p g ( )Computerized material Resource Planning (MRP)NC part programmingNC part programmingRobot ProgrammingComputerized SchedulingComputerized process controlComputerized process controlComputerized Manufacturing Control by FMSSh fl t lShop floor controlComputer Aided Quality Control (CAQC)Computer Aided Inspection

AutomationAutomationAutomation is the process of following a predeterminedsequence of operations with little or no human interventionsequence of operations with little or no human intervention,using specialized equipment and devices that perform andcontrol the manufacturing process.g pWhy go for Automation?1. Increased productivityp y2. Reduced cost of labour3. Improved quality3. Improved quality4. Reduced in‐process inventory5 Reduce Manufacturing time5. Reduce Manufacturing time6. Increased safetyThere are three types of AutomationThere are three types of Automation1. Fixed Automation2 Programmable Automation2. Programmable Automation3. Flexible Automation

AutomationAutomationFixed Automation

It is also known as hard automation.

Used to produce a standardized product.

Used for very large quantity production of one or few

marginally different componentsmarginally different components.

Highly specialized tools, devices, equipment, specialHighly specialized tools, devices, equipment, special

purpose machine tools, are utilized to produce a

product.

Very efficient, high production rate , low unit cost.For-2013 (IES, GATE & PSUs) Page 26

AutomationAutomationProgrammable Automationg

Can change the design of the product or even change theg g p g

product by changing the program.

Used for the low quantity production of large number of

different components.

Equipment are designed to be flexible or programmable.

Used for batch production.

AutomationAutomationFlexible Automation

If is also known as FMS, and uses CAD/CAM,

Produce different products on the same equipment inp q p

any order or mix.

What is an FMS?A flexible manufacturing system (FMS) is aA flexible manufacturing system (FMS) is amanufacturing system in which there is some

f fl ibili h ll hamount of flexibility that allows the system toreact in the case of changes.gTwo categories of flexibility

M hi fl ibilit th t ' bilit t bMachine flexibility, covers the system's ability to bechanged to produce new product types, and ability toh h d f i dchange the order of operations executed on a part.Routing flexibility, which consists of the ability tog y yuse multiple machines to perform the same operationon a part, as well as the system's ability to absorbp y ylarge‐scale changes, such as in volume, capacity, orcapability.

FMS ComponentsMost FMS systems comprise of three mainsystemsy

Work machines (typically automated CNCmachines) that perform a series of operations;machines) that perform a series of operations;An integrated material transport system and acomputer that controls the flow of materials,tools, and information (e.g. machining data, ( g gand machine malfunctions) throughout thesystem;system;Auxiliary work stations for loading and

l d lunloading, cleaning, inspection, etc.

FMS GoalsReduction in manufacturing cost by lowering directReduction in manufacturing cost by lowering directlabor cost and minimizing scrap, re‐work, and material

twastage.Less skilled labor required.qReduction in work‐in‐process inventory by eliminatingthe need for batch processingthe need for batch processing.Reduction in production lead time permittingmanufacturers to respond more quickly to the variabilityof market demand.Better process control resulting in consistent quality.

Advantages of FMSF t l t h f t t thFaster, lower‐ cost changes from one part to anotherwhich will improve capital utilizationLower direct labor cost, due to the reduction in numberof workersReduced inventory, due to the planning andprogramming precisionp g g pConsistent and better quality, due to the automatedcontrolcontrolLower cost/unit of output, due to the greater

d ti it i th b f kproductivity using the same number of workersSavings from the indirect labor, from reduced errors,rework, repairs and rejects

Disadvantages of FMSLi i d bili d h i d dLimited ability to adapt to changes in product or productmix (e.g., machines are of limited capacity and thetooling necessary for products, even of the same family,is not always feasible in a given FMS)y g )Substantial pre‐planning activity

ll f d llExpensive, costing millions of dollarsTechnological problems of exact component positioningec o og ca p ob e s o e act co po e t pos t o gand precise timing necessary to process a componentS hi ti t d f t i tSophisticated manufacturing systems

Reference BookCAD/CAM: Computer‐Aided Design and Manufacturing By GrooverCNC Machines By B. S. Pabla, M. AdithanMachine tool design and numerical control By Machine tool design and numerical control ‐ By MehtaC C l Of M S B KComputer Control Of Manu. Systems By Koren

Ch 11: NC CNC RoboticsCh‐11: NC, CNC, RoboticsQ. No Option Q. No OptionQ p Q p1 A 9 B2 B 10 D3 A 11 A3 A 11 A4 A 12 C4 A 12 C5 D 13 D6 A 14 A

A C7 A 15 C8 A 16 B8 A 16 B

17 AFor-2013 (IES, GATE & PSUs) Page 27

LatheLathe


hLatheA l th i l hi th t t t th k dA lathe is a large machine that rotates the work, andcutting is done with a non‐rotating cutting tool. Theh t ll d h li l Th t l ishapes cut are generally round, or helical. The tool istypically moved parallel to the axis of rotation during

tticutting.head stock ‐ this end of the lathe contains the driving motor and gears. Power to rotate the part is delivered from here. This typically has levers that let the speeds and feeds be set.ways ‐ these are hardened rails that the carriage rides ways these are hardened rails that the carriage rides on.tail stock ‐ this can be used to hold the other end of the tail stock ‐ this can be used to hold the other end of the part.

hLatheB dBed ‐ this is a bottom pan on the lathe that catches chips,cutting fluids, etc.

carriage ‐ this part of the lathe carries the cutting tool andmoves based on the rotation of the lead screw or rodmoves based on the rotation of the lead screw or rod.Lead screw ‐ A large screw with a few threads per inch usedf i h d I h ACME h d i h i l d d lfor cutting threads. It has ACME threads with included angleof 29o for easy engagement and disengagement of half nut.Lead rod ‐ a rod with a shaft down the side used for drivingnormal cutting feeds.gThe critical parameters on the lathe are speed of rotation(speed in RPM) and how far the tool moves across the work(speed in RPM) and how far the tool moves across the workfor each rotation (feed in IPR)

General classifications used when describing lathesS i h l di f k h b dSwing ‐ the largest diameter of work that can be rotated.Distance Between Centres ‐ the longest length ofg gworkpieceLength of Bed Related to the Distance BetweenLength of Bed ‐ Related to the Distance BetweenCentresPower ‐ The range of speeds and feeds, and thehorsepower availableo sepo e ava ab e

Number of Spindle SpeedN b f i dl d i i i iNumber of spindle speed is in a geometric progression.If n number of spindle speed is required with N1 is thep p q 1minimum speed then

132 −nNNNNN1

11

31

2111 ....,.........,,,

− == n

n

NrNandNNrNrNrNrNN

11

max1min1

⎞⎛

==

nN

NrNandNN

( )1

min

maxRatioStepTherefore,−

⎟⎟⎠

⎞⎜⎜⎝

⎛=

n

NNr

The values of step ratios are 1.06, 1.12, 1.26, 1.41, 1.58 and 2min ⎠⎝

TurningT i d h d i h id di Turning ‐ produces a smooth and straight outside radius on a part.

Th diThreadingTh di Th i l i d i kl i Threading ‐ The cutting tool is moved quickly cutting threads.


ThreadingI l i f h i dl i l In one revolution of the spindle, carriage must travel the pitch of the screw thread to be cut.

tbtth dthfPit hLLss

PLzNPzN =

screwleadtheofPitchLcutbetothreadscrewtheofPitchP

==

l dhffbcutbetothreadscrewtheofstartofNumbersz =

( ) ( ) traingear carriageto spindleofratiogearscrewleadtheofstartofNumber

Lscg

L

NNiz

==

( ) ( )ggpg Lscg

F iFacingF i Th d f h i d bFacing ‐ The end of the part is turned to be square.

T iTaperingT i h l i ( Tapering ‐ the tool is moves so as to cut a taper (cone shape).

/ l /Parting/Slotting/GroovingA l i d i / f h k h ll ill lA tool is moved in/out of the work. shallow cut will leavea formed cut, a deep cut will cut off the unsupportedpart.

ll /Drilling/BoringD illi /B i d ill bi i h d i hDrilling/Boring ‐ a cutter or drill bit is pushed into theend to create an internal feature.

lKnurlingK li i f i h bKnurling is a manufacturing process whereby avisually‐attractive diamond‐shaped (criss‐cross)pattern is cut or rolled intometal.This pattern allows human hands or fingers to get aThis pattern allows human hands or fingers to get abetter grip on the knurled object than would beprovided by the originally smoothmetal surfaceprovided by the originally‐smoothmetal surface.

SpinningM l S i i i b hi h i l f lMetal Spinning is a process by which circles of metal areshaped over mandrels (also called forms) while mountedon a spinning lathe by the application of levered forcewith various tools.

ReaminggA reamer enters the workpiece axially through the endA reamer enters the workpiece axially through the endand enlarges an existing hole to the diameter of thetool Reaming removes a minimal amount of materialtool. Reaming removes a minimal amount of materialand is often performed after drilling to obtain both amore accurate diameter and a smoother internalmore accurate diameter and a smoother internalfinish.


Tappingpp gA tap enters the workpiece axially through the end andcuts internal threads into an existing hole Thecuts internal threads into an existing hole. Theexisting hole is typically drilled by the required tapd ill i th t ill d t th d i d tdrill size that will accommodate the desired tap.

k h ld f hWork holding Devices for LathesH ld bHeld between centers3 jaw self centering chuck (Disc type jobs being held3 j g ( yp j gin chucks )4 jaw independently adjusted chuck4 jaw independently adjusted chuckHeld in a collet (Slender rod like jobs being held incollets )Mounted on a face plate (Odd shape jobs being heldMounted on a face plate (Odd shape jobs, being heldin face plate)

d hMounted on the carriageMandrelsMandrelsMagnetic chuck – for thin job

h h kLathe chucksL th h k d t t id i t fLathe chucks are used to support a wider variety ofworkpiece shapes and to permit more operations to be

f d th b li h d h th k iperformed than can be accomplished when the work isheld between centers.Three‐jaw, self‐centering chucks are used for work thathas a round or hexagonal cross section.Each jaw in a four‐jaw independent chuck can be movedinward and outward independent of the others by meansa d a d out a d depe de t o t e ot e s by ea sof a chuck wrench. Thus they can be used to support awide variety of work shapes.wide variety of work shapes.Combination four‐jaw chucks are available in which eachjaw can be moved independently or can be movedjaw can be moved independently or can be movedsimultaneously by means of a spiral cam.

3 Jaw Chuck 4 Jaw Chuck3 J

Collets Magnetic Chuck

Face Plate

Turning

l fFormula for TurningD h f

−1 2D Dd DOCDepth of cut,Average diameter of workpiece

= = 1 2d DOC mm2

+1 2D DDAverage diameter of workpiece = 1 2avgD mm

2

Cutting Time, + +=

L A OCTfN

Metal Removal Rate

fN

( )2 2D DMetal Removal Rate ( )π − π= = π

2 21 2

a v g

D DM R R D d fN

4 / fN

Cutting Speed, V = π 1D N ,m / min10001000

hTurning Tapers on LathesUsing a compound slide,

Using form tools,g

Offsetting the tailstock andOffsetting the tailstock, and

U i t t i tt h tUsing taper turning attachment.

U i C d SlidUsing a Compound SlideLimited movement of the compound slideted ove e t o t e co pou d s deFeeding is by hand and is non‐uniform. This is

ibl f l d ti it d fresponsible for low‐productivity and poor surfacefinish.Can be employed for turning short internal andexternal tapers with a large angle of (steep) taper.external tapers with a large angle of (steep) taper.


Using a Compound Slide contd..The angle is determined by

dD −ldD

2tan =αangletaperHalfα

stockofDiameterDangletaperHalf

==α

tapertheoflengthldiametersmallerd

==

tapertheoflengthl

Offsetting the tailstockI i h il k ff h iIt is necessary to measure the tailstock offset when usingthis method.This method is limited to small tapers (Not exceeding 8o

) over long lengths) over long lengths.By offsetting the tailstock, the axis of rotation of the job

l d b h h lf l fis inclined by the half angle of taper.

Offsetting the tailstock Contd..T il k ff (h) b d i d bTailstock offset (h) can be determined by

( ) LhdDLh −( ) αtan2

Lhorl

dDLh ==

lForm toolS i l f l f i h i d ThSpecial form tool for generating the tapers is used. Thefeed is given by plunging the tool directly into the work.This method is useful for short external tapers, wherethe steepness is of no consequence, such as forp q ,chamfering.

T T i A hTaper Turning AttachmentAddi i l i i h d h f h l hAdditional equipment is attached at the rear of the lathe.The cross slide is disconnected from the cross feed nut.The cross slide is then connected to the attachment.A h i i d d l l h b d hAs the carriage is engaged, and travels along the bed, theattachment will cause the cutter to move in/out to cutthe taper.For turning tapers over a comprehensive range is the useFor turning tapers over a comprehensive range is the useof taper turning attachment.

lErrors in tool settings

Setting the tool below the centre decrease actual rake angle,Setting the tool below the centre decrease actual rake angle,while clearance angle increases by the same amount. Thuscutting force increasedcutting force increased.Setting the tool above the centre causes the rake angle toincrease hile clearance angle reduces More rubbing ithincrease, while clearance angle reduces. More rubbing withflank.

hTurret LatheA l h b f l b hA turret lathe, a number of tools can be set up on themachine and then quickly be brought successively intoworking position so that a complete part can bemachined without the necessity for further adjusting,y j g,changing tools, or making measurements.

Turret LatheTurret Lathe


Capstan LatheCapstan LatheCapstan lathe Turret latheSh t lid i th ddl i S ddl l th b dShort slide, since the saddle isclamped on the bed in position.

Saddle moves along the bed,thus allowing the turret to be oflarge sizelarge size.

Light duty machine, generally for Heavy duty machine, generallycomponents whose diameter isless than 50 mm.

for components with largediameters, such as 200 mm.

Too much overhang of the turretwhen it is nearing cut.

Since the turret slides on thebed, there is no such difference.when it is nearing cut. bed, there is no such difference.

Ram‐type turret lathe, the ram andthe turret are moved up to the

Saddle‐type lathes, the mainturret is mounted directly on thethe turret are moved up to the

cutting position by means of thecapstan Wheel As the ram is

turret is mounted directly on thesaddle, and the entire saddleand turret assemblycapstan Wheel. As the ram is

moved toward the headstock, theturret is automatically locked into

and turret assemblyreciprocates.

turret is automatically locked intoposition.

Turret indexing mechanismThe hexagonal turret is rotated (for indexing) by a

Geneva mechanism where a Geneva disc having six

di l l i d i b l i i B f iradial slots is driven by a revolving pin. Before starting

rotation the locking pin is withdrawn by a cam leverrotation, the locking pin is withdrawn by a cam lever

mechanism. The single rotation of the disc holding theg g

indexing pin is derived from the auxiliary shaft with the

help of another single revolution clutch as indicated.

For automatic lathe: Ratchet and Pawl mechanism

hAutomatic LatheTh i i h l l li d b iThe term automatic is somewhat loosely applied, but isnormally restricted to those machine tools capable ofproducing identical pieces without the attention of anoperator, after each piece is completed. Thus, afterp , p p ,setting up and providing an initial supply of material,further attention beyond replenishing the materialfurther attention beyond replenishing the materialsupply is not required until the dimensions of the worki h i t t lpieces change owing to tool wear.

A number of types of automatic lathes are developedyp pthat can be used for large volume manufactureapplication, such as single spindle automatics, Swiss typeapplication, such as single spindle automatics, Swiss typeautomatics, and multi‐spindle automatics.

Swiss type Automatic Lathe Or Sliding Headstock Automatics

Headstock travels enabling axial feed of the bar stockHeadstock travels enabling axial feed of the bar stockagainst the cutting tools.h l kThere is no tailstock or turret

High spindle speed (2000 – 10,000 rpm) for small jobHigh spindle speed (2000 10,000 rpm) for small jobdiameterTh tti t l ( t fi i b i l di tThe cutting tools (upto five in number including two onthe rocker arm) are fed radiallyUsed for lot or mass production of thin slender rod ortubular jobs, like components of small clocks and wristtubular jobs, like components of small clocks and wristwatches, by precision machining.

Multi Spindle Automatic LatheFor increase in rate of production of jobs usually of

ll i d i l tsmaller size and simpler geometry.

Having four to eight parallel spindles are preferably usedHaving four to eight parallel spindles are preferably used.

Multiple spindle automats also may be parallel action orMultiple spindle automats also may be parallel action or

progressively working type.p g y g yp

N T bl i k h G bNorton type Tumbler‐gear quick‐change Gear box Norton type Tumbler‐gear quick‐change Gear box

It i f t 8 t d h ft SIt comprises a cone of gears 1 to 8 mounted on shaft S2.

The tumbler gear can slide on shaft S1. It can mesh with anyThe tumbler gear can slide on shaft S1. It can mesh with any

gear on shaft S2 through an intermediate gear which is

located on a swinging and sliding lever so that it can engage

t 8 f diff t di t h ft Sgears 1 to 8 of different diameters, on shaft S2.

The lever can be fixed in any desired ratio position with theThe lever can be fixed in any desired ratio position with the

help of a stop pin.

The drive is usually from the driving shaft S1 to the driven

shaft S2.For-2013 (IES, GATE & PSUs) Page 32

Ch – 2: Lathe

Q. No Option Q. No Option

1 C 6 A

2 A 7 B2 A 7 B

3 D 8 B3 D 8 B

4 B 9 D4 B 9 D

5 B 10 C5 B 10 C

DrillingDrilling

B S K M d lBy S K Mondal

llDrillingD illi i i h li d i l h lDrilling is a operation that cuts cylindrical holes.

TYPES OF DRILL PRESSESVertical or pillar type

Radial Arm type

Gang drill

Multi Spindle drill

N i l C l d illNumerical Control drill

llDrilling Operations Chip formation of a drillof a drill

DrillDrillThe twist drill does most of the cutting with the tip ofth bitthe bit.

•There are flutesto carry the chipsup from theup from thecutting edges tothe top of thethe top of thehole where they

t ffare cast off.

llDrill llDrillAxial rake angle is the angle between the face and the line

parallel to the drill axis At the periphery of the drill it isparallel to the drill axis. At the periphery of the drill, it is

equivalent to the helix angle.

The lip clearance angle is the angle formed by the portion of

the flank adjacent to the land and a plane at right angles to

the drill axis measured at the periphery of the drillthe drill axis measured at the periphery of the drill.

Lead of the helix is the distance measured parallel to the drillp

axis, between corresponding point on the leading edge of the

land in one complete revolution.For-2013 (IES, GATE & PSUs) Page 33

llDrillDrill sizes are typically measured across the drill points with

i ta micrometer

Most widely used material is High Speed SteelMost widely used material is High Speed Steel

The drill blanks are made by forging and then are twisted toe d b a s a e ade by o g g a d t e a e t sted to

provide the torsional rigidity. Then the flutes are machined

and hardened before the final grinding of the geometry.

Deep hole drilling requires special precautions to take care of

th l f l l f hithe removal of large volume of chips.

Point Angle (2β)The point angle is selected to suit the hardness and brittleness ofp gthe material being drilled.Harder materials have higher point angles, soft materials haveg p g ,lower point angles.An increase in the drill point angle leads to an increase in thep gthrust force and a decrease in the torque due to increase of theorthogonal rake angle.

( )This angle (half) refers to side cutting edge angle of a single pointtool.S d d P i A l i 8°Standard Point Angle is 118°It is 116° to 118° for medium hard steel and cast ironIt is 125° for hardened steelIt is 130° to 140° for brass and bronzeIt is only 60° for wood and plastics

Helix Angle (ψ)Helix angle is the angle between the leading edge of theHelix angle is the angle between the leading edge of theland and the axis of the drill. Sometimes it is also called

i l las spiral angle.The helix results in a positive cutting rakep gThis angle is equivalent to back rake angle of a singlepoint cutting toolpoint cutting tool.Usual – 20° to 35° – most commonLarge helix : 45° to 60° suitable for deep holes and softerwork materialswork materialsSmall helix : for harder / stronger materialsZero helix : spade drills for high production drillingmicro‐drilling and hard work materials

C i S d i D illiCutting Speed in DrillingTh i d i d illi i h f d f h The cutting speed in drilling is the surface speed of the twist drill.

DN / min1000

DNV mπ=

1000

llDrilling TimeTi f d illi h h lTime for drilling the hole

L , minLTfN

=fN

llMRR in Drilling2

3 / minDMRR fN mmπ⎛ ⎞= ⎜ ⎟ , / min

4MRR fN mm= ⎜ ⎟

⎝ ⎠

S F l f D illiSome Formulae for DrillingD( )

2 tanDConeheight hβ

=

( ) sin2fUncut chip thickness t β=

( )2sin

DWidthof cut bβ

=

( )1

2sin2 / tan

( ) tr D

O th l k l

β

ψ− ⎡ ⎤⎢ ⎥( )1( ) tan

sinOrthogonal rakeangle α

β= ⎢ ⎥

⎣ ⎦

Reaming, Boring, BroachingReaming, Boring, Broaching


Reaming


ReamingR i ll t f t i l f thReaming removes a small amount of material from thesurface of holes.I i d f b i h lIt is done for two purposes: to bring holes to a more exactsize and to improve the finish of an existing hole.M l i i l h h fl hi h bMultiage cutting tools that has many flutes, which may bestraight or in a helix are used.No special machines are built for reaming. The samemachine that was employed for drilling the hole can be usedf i b h i h i lfor reaming by changing the cutting tool.Only a minimum amount of materials should be left for

l b l l d bl dremoval by reaming. As little as 0.1 mm is desirable, and inno case should the amount exceed 0.4 mm.A properly reamed hole will be within 0.025 mm of thecorrect size and have a fine finish.

Reamer

Reamer FlutesReamer FlutesThe reamer flutes are either straight or helical.The helical flutes promote smoother cutting and should beused specifically for holes that are not continuous, such asthose with keyways parallel to the axis of the hole.The cutting action of the helical flutes is smoother and helpsgin preventing chatter.The reamers are termed as left hand or right hand,g ,depending upon the direction in which they are moved,looking from the shank to the cutting portion.The right‐hand reamer with right‐hand helix is used forroughing cuts, since the tool tends to go into the workpieceg g g pmore efficiently and thereby promotes the material removal.A right‐hand reamer with left‐hand flutes is used forgfinishing cuts.

fTypes of ReamersTh i i l f The principal types of reamers are:1. Hand reamers

a. Straight b Tb. Taper

2. Machine or chucking reamers ga. Roseb l db. Fluted

3. Shell reamers3. Shell reamers4. Expansion reamers5. Adjustable reamers

ReamingT li i i l di b h fi i h dTo meet quality requirements, including both finish andaccuracy (tolerances on diameter, roundness,straightness, and absence of bell‐mouth at ends ofholes). Reamers must have adequate support for the) q ppcutting edges, and reamer deflection must be minimal.Reaming speed is usuall t o thirds the speed forReaming speed is usually two‐thirds the speed fordrilling the same materials. However, for close tolerances

d f f h d h ld b land fine finish, speeds should be slower.Feeds are usually much higher than those for drillingFeeds are usually much higher than those for drillingand depend upon material.R d d tti fl id th th fRecommended cutting fluids are the same as those fordrilling.

ReamingR lik d ill h ld t b ll d t b d llReamers, like drills, should not be allowed to become dull.The chamfer must be reground long before it exhibitsexcessive wear Sharpening is usually restricted to theexcessive wear. Sharpening is usually restricted to thestarting taper or chamfer. Each flute must be ground exactlyevenly or the tool will cut oversizeevenly or the tool will cut oversize.Reamers tend to chatter when not held securely, when thework or work holder is loose or when the reamer is notwork or work holder is loose, or when the reamer is notproperly ground.Irregularly spaced teeth may help reduce chatter Other curesIrregularly spaced teeth may help reduce chatter. Other curesfor chatter in reaming are to reduce the speed, vary the feedrate chamfer the hole opening use a piloted reamer reducerate, chamfer the hole opening, use a piloted reamer, reducethe relief angle on the chamfer, or change the cutting fluid.Any misalignment between the work piece and the reamerAny misalignment between the work piece and the reamerwill cause chatter and improper reaming.

Rose ReamerRose ReamerRose chucking reamersRose chucking reamersare ground cylindricaland have no reliefand have no reliefbehind the outer edgesf h h All iof the teeth. All cutting

is done on the beveledends of the teeth

Chucking ReamerChucking ReamerFluted chuckingFluted chuckingreamers have reliefbehind the edges of thebehind the edges of theteeth as well as beveled

d Thends. They can cut onall portions of the teeth.Their flutes arerelatively short and theyy yare intended for lightfinishing cutsfinishing cuts.


Shell ReamerShell ReamerShell reamers often areShell reamers often areused for sizes over 20mm to save cutting toolmm to save cutting‐toolmaterial. The shell,

d f HSS f llmade of HSS for smallersizes and with carbideedges for larger sizes orfor mass‐productionpwork.

Trepanningp gTrepanning is a annular groove producing operationwhich leaves a solid cylindrical core in the centre Inwhich leaves a solid cylindrical core in the centre. Intrepanning a cutter consisting of one or more cuttingedges placed along the circumference of a circle is usededges placed along the circumference of a circle is usedto produce the annular groove.

Trepanning Tool

Boringg

B iBoringB i l i l h l i f i i h lBoring always involves the enlarging of an existing hole,which may have been made by a drill or may be the result of acore in a casting.An equally important and concurrent purpose of boring mayq y p p p g ybe to make the hole concentric with the axis of rotation ofthe workpiece and thus correct any eccentricity that mayp y y yhave resulted from the drill drifting off the centerline.Concentricity is an important attribute of bored holes.Concentricity is an important attribute of bored holes.When boring is done in a lathe, the work usually is held in achuck or on a faceplate Holes may be bored straightchuck or on a faceplate. Holes may be bored straight,tapered, or to irregular contours.

ll l h l f d h lBoring is essentially internal turning while feeding the toolparallel to the rotation axis of the workpiece.

BoringTh i i l d f b i f iThe same principles are used for boring as for turning.The tool should be set exactly at the same height as they gaxis of rotation. Slightly larger end clearance anglessometimes have to be used to prevent the heel of the toolsometimes have to be used to prevent the heel of the toolfrom rubbing on the inner surface of the hole.

BoringB h l h ill b f d dBecause the tool overhang will be greater, feeds anddepths of cut may be somewhat less than for turning toprevent tool vibration and chatter.In some cases the boring bar may be made of tungstenIn some cases, the boring bar may be made of tungstencarbide because of this material's greater stiffness.h b l l lThe boring tool is a single‐point cutting tool.

Hole quality, finish boring can typically achieve holeso e qua ty, s bo g ca typ ca y ac eve o eswithin tolerances of IT9.S f fi i h b tt th R i b hi dSurface finishes better than Ra 1 micron can be achieved.

l fFormula for Boring

Average diameter of workpiece += 1 2D DD mmAverage diameter of workpiece =avgD mm

2

Cutting Time, + +=

L A OCTfN

Metal Removal Rate

fN

Metal Removal Rate( )π − π2 2

1 2D D( )= = π

1 2a v gM R R D d fN

4 / fN

Broaching


B hiBroachingB hi i lti l t th tti ti ith thBroaching is a multiple‐tooth cutting operation with thetool reciprocating.Since in broaching the machining operation iscompleted in a single‐stroke as the teeth on the cuttingtool, called broach, are at gradually increasing heightcorresponding to the feed per tooth of a milling cutter.The shape of the broach determines the shape of themachined part.ac ed pa t.Broaching was originally developed for machininginternal keyways but looking at the advantages it hasinternal keyways, but looking at the advantages, it hasbeen extensively used in the mass production ofautomobile component manufacture for various otherautomobile component manufacture for various othersurfaces as well.

BroachingTh i l l i h b h h i hThe material removal using the broach teeth is shownschematically in Fig. shown in below. The dotted line inthe figure indicates the amount of material beingremoved by successive individual teeth.y

hBroach Construction

hBroach ConstructionTh b h i d f i f h h hThe broach is composed of a series of teeth, each toothstanding slightly higher than the previous one. This riseper tooth is the feed per tooth and determines thematerial removed by the tooth.yThere are basically three sets of teeth present in a broachas sho n in Fig sho n abo eas shown in Fig. shown above.The roughing teeth that have the highest rise per toothremove bulk of the material.The semi‐finishing teeth whose rise per tooth is smallerThe semi‐finishing teeth, whose rise per tooth is smaller,remove relatively smaller amounts of material comparedt th hi t thto the roughing teeth.

hBroach ConstructionTh l f h i ll d h fi i hi i i hThe last set of teeth is called the finishing or sizing teeth.Very little material will be removed by these teeth.The necessary size will be achieved by these teeth andhence all the teeth will be of the same size as thathence all the teeth will be of the same size as thatrequired finally. With the progress of time, when thefirst set of teeth ear out the ne t set of teeth ill befirst set of teeth wear out, the next set of teeth will beable to provide the sizing function.The pull end of the broach (Fig. shown in above) isattached to the pulling mechanism of the broachingattached to the pulling mechanism of the broachingmachine with the front pilot aligning the broachproperly with respect to the workpiece axis before theproperly with respect to the workpiece axis before theactual cutting starts.

hBroach ConstructionTh il h l k h b h iThe rear pilot helps to keep the broach to remain squarewith the workpiece as it leaves the workpiece afterbroaching.Broaching speeds are relatively low of the order of 6 to 15Broaching speeds are relatively low, of the order of 6 to 15m/min. However, the production rate is high with thec cle times being about to 30 seconds including thecycle times being about 5 to 30 seconds, including theworkpiece and tool handling times. The low cutting

d d h h l l f hspeeds are conducive to very high tool life with verysmall tool wear rates.

hBroach ConstructionB h ll d f hi h d l i iBroaches are generally made of high speed steel in viewof its high impact strength. Sometimes, the titaniumnitride coating helps to improve the tool life further.Also, the carbide insert‐type broaches are used more for, ypsurface broaching of cast iron for very large volumeproduction to reduce the frequent resharpening of theproduction to reduce the frequent resharpening of thebroach, which is a very difficult operation.

d d b h l bl f dStandard broaches are available for common and moreoften used forms, such as round and square holes,qkeyways, etc.

hBroach ConstructionF h i i i i l h lFor smooth operation, it is essential that at least two orthree teeth be simultaneously engaged.The thumb rule for tooth spacing,The cut per tooth f is kept in the range 0 05 mm 0 09

1.75 ,s l mm=The cut per tooth f is kept in the range 0.05 mm – 0.09mm.In the normal speed BUE may be a problem. To avoidthis a copious supply of the cutting fluid is provided.t s a cop ous supp y o t e cutt g u d s p ov ded.

d f b hAdvantages of broaching1 It is the fastest way of finishing an operation with a single1. It is the fastest way of finishing an operation with a singlestroke.2 Since all the machining parameters are built into the2. Since all the machining parameters are built into thebroach, very little skill is required from the operator.3 Broaching machine is simple since only a single3. Broaching machine is simple since only a singlereciprocating motion is required for cutting.4. Final cost of the machining operation is one of the lowest4 g pfor mass production.5. Any type of surface, internal or external, can be generated5 y yp gwith broaching.6. Many surfaces, which are very difficult or impossible byh b d b b hi F lother means, can be done by broaching. For example, square

hole and internal splines.G d f fi i h d fi di i l t l b7. Good surface finish and fine dimensional tolerances can be

achieved by broaching, often better than boring or reamingFor-2013 (IES, GATE & PSUs) Page 37

f b hLimitations of broachingC t d b h i d1. Custom made broaches are very expensive and can

therefore be justified only for very large volumed tiproduction.

2. A broach has to be designed for a specific applicationand can be used only for that application. Hence, thelead time for manufacture is more for custom designedbroaches.3. Broaching, being a very heavy metal removal3. oac g, be g a ve y eavy eta e ovaoperation, requires that the workpiece is rigid andcapable of withstanding the large forces.capable of withstanding the large forces.4. Broaching can only be carried out on the workpiecewhose geometry is such that there is no interference forwhose geometry is such that there is no interference forthe broach movement for the cutting.

Ch‐6: Drilling, Boring & ReamingQ. No Option Q. No Option1 A 8 D

D A2 D 9 A3 A 10 B3 A 10 B4 B 11 C4 B 11 C5 C 12 C56 B 13 B7 D

MillingMilling


llMillingMilli hi f i id l dMilling machines of various types are widely usedfor the following purposes using proper cuttingtools called milling cutters:Flat surface in vertical horizontal and inclined planesFlat surface in vertical, horizontal and inclined planesMaking slots or ribs of various sectionsSlitting or partingOften producing surfaces of revolutionOften producing surfaces of revolutionMaking helical grooves like flutes of the drillsLong thread milling on large lead screws, power screws,worms etc and short thread milling for small sizeworms etc and short thread milling for small sizefastening screws, bolts etc.

llMilling2‐D contouring like cam profiles, clutches etc and 3‐D

l k d ldcontouring like die or mould cavities

C i h i i b h d i fCutting teeth in piece or batch production of spur gears,

straight toothed bevel gears worm wheels sprocketsstraight toothed bevel gears, worm wheels, sprockets,

clutches etc.

Producing some salient features like grooves, flutes,g g

gushing and profiles in various cutting tools, e.g., drills,

taps, reamers, hobs, gear shaping cutters etc.

Up milling and down milling

ll d d llUp milling and down millingI d illi h h h i h f ll hiIn down milling, though the cut starts with a full chipthickness, the cut gradually reduces to zero. This helps ineliminating the feed marks present in the case of upmilling and consequently better surface finish.g q yClimb milling also allows greater feeds per tooth andlonger cutting life bet een regrinds than thelonger cutting life between regrinds than theconventional milling.Up milling needs stronger holding of the job and downmilling needs backlash free screw‐nut systems formilling needs backlash free screw nut systems forfeeding.

d f llAdvantages of Down MillingS i d hi hi d h d h ld i1. Suited to machine thin and hard‐to‐hold parts since

the workpiece is forced against the table or holdingdevice by the cutter.2 Work need not be clamped as tightly2. Work need not be clamped as tightly.3. Consistent parallelism and size may be maintained,

l l hparticularly on thin parts.4. It may be used where breakout at the edge of the4. t ay be used e e b ea out at t e edge o t eworkpiece could not be tolerated.

It i t % l t t b thi th d5. It requires upto 20% less power to cut by this method.6. It may be used when cutting off stock or when millingy g gdeep, thin slots.

d f llDisadvantages of Down Milling

1. It cannot be used unless the machine has a backlash

eliminator and the table jibs have been tightened.

2 It cannot be used for machining castings or hot rolled2. It cannot be used for machining castings or hot rolled

steel since the hard outer scale will damage the cuttersteel, since the hard outer scale will damage the cutter.


l f f ll hClassification of milling machines( ) A di f f(a) According to nature of purposes of use:

General purposep pSingle purposeS i lSpecial purpose

(b) According to configuration and motion of the( ) g gwork‐holding table / bed

K tKnee typeBed typeypPlaner typeR t t bl tRotary table type

l f f ll hClassification of milling machines( ) A di t th i t ti f th i dl ( )(c) According to the orientation of the spindle(s).

Plain horizontal knee typeHorizontal axis (spindle) and swiveling bed typeVertical spindle typep ypUniversal head milling machine

(d) According to mechanization / automation and(d) According to mechanization / automation andproduction rate

Hand mill (milling machine)Hand mill (milling machine)Planer and rotary table type vertical axis milling machinesT ll d illi hiTracer controlled copy milling machine,Milling machines for short thread millingComputer Numerical Controlled (CNC) milling machine

l f f llClassifications of milling cutters( ) P fil h d h h f(a) Profile sharpened cutters – where the geometry ofthe machined surfaces are not related with the toolshape, viz;i Slab or plain milling cutter: – straight or helicali. Slab or plain milling cutter: straight or helicalfluted

S d ll l d b h d dii. Side milling cutters – single side or both sided typeiii. Slotting cutter. S ott g cutteiv. Slitting or parting tools

d ll h h h kv. End milling cutters – with straight or taper shankvi. Face milling cutters.vi. Face milling cutters.

l f f llClassifications of milling cutters(b) F li d h h j b fil(b) Form relieved cutters – where the job profilebecomes the replica of theTool‐form, e.g., viz.;i Form cuttersi. Form cuttersii. Gear (teeth) milling cuttersiii. Spline shaft cuttersi T l f ttiv. Tool form cuttersv. T‐slot cuttersvi. Thread milling cutter

l b l llSlab or Plain milling cutters d d l llSide and slot milling cutters

l lSlitting saw or parting tool d ll d llEnd milling cutters or End mills llFace milling cutters


Use of form relieved cutters (milling) Tool form cutters lT‐ slot cutter

h llGear teeth milling cutters l h fSpline shaft cutters ddl llStraddle milling

llGang milling Turning by rotary tools (milling cutters) dIndexing


l l dSimple or Plain IndexingPl i i d i i h i h i d i h dPlain indexing is the name given to the indexing methodcarried out using any of the indexing plates inconjunction with the worm.

ll lMilling VelocityTh i d i illi i h f d f hThe cutting speed in milling is the surface speed of themilling cutter.

DNV π=V

1000

llMilling Time

Time for one pass = minutesL 2 A+ ×p

A h di

fZN2 2D D⎛ ⎞ ⎛ ⎞Approach distance, ( )D DA d d D d

2 2⎛ ⎞ ⎛ ⎞= − − = −⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

llMRR in MillingC id i h d fi d i h di i f Considering the parameters defined in the discussion of speeds and feeds, etc, the MRR is given below,Where,

MRR = w d F× ×where, w = width of cut, d = depth of cut

Some Formulae for MillingSome Formulae for Milling

max2Maximum uncut chip thickness (t ) f dNZ D

=

A hi hi k ( )

NZ Df d

a

2

Average uncut chip thickness (t )vgf

NZ D=

2

max 2 2Peak to valley surface roughness (h )4

fDN Z

=4DN Z

Ch 7 MilliCh‐7: MillingQ No Option Q. No Option

B D1 B 7 D

B 8 D2 B 8 D

D A3 D 9 A

A D4 A 10 D

5 C 11 C5 C 11 C

6 D 12 D6 D 12 D

Gear Manufacturingg

By S K Mondal

f fManufacture of GearsManufacture of gears needs several processing operations inManufacture of gears needs several processing operations insequential stages depending upon the material and type of thegears and quality desired. Those stages generally are:g q y g g y

Preforming the blank without or with teethAnnealing of the blank, if required, as in case of forged org , q , gcast steelsPreparation of the gear blank to the required dimensionsb hby machiningProducing teeth or finishing the preformed teeth by

hi imachiningFull or surface hardening of the machined gear (teeth), ifrequiredrequiredFinishing teeth, if required, by shaving, grinding etcI ti f th fi i h dInspection of the finished gears

dForming and GenerationGear teeth are produced by machining based on

Forming – where the profile of the teeth are obtained as

the replica of the form of the cutting tool (edge); e gthe replica of the form of the cutting tool (edge); e.g.,

milling, broaching etc.milling, broaching etc.

Generation – where the complicated tooth profile arep p

provided by much simpler form cutting tool (edges)

through rolling type, tool – work motions, e.g., hobbing,

gear shaping etc.For-2013 (IES, GATE & PSUs) Page 41

Sunderland method using rack type cutterTh k HSS (h i k dThe rack type HSS cutter (having rake andclearance angles) reciprocates to accomplish theclearance angles) reciprocates to accomplish themachining (cutting) action while rolling typei t ti ith th bl k lik i f kinteraction with the gear blank like a pair of rackand pinion.p

External gear teeth generation by rack type cutter (Sunderland method)

Sunderland method using rack type cutterApplications of this method (and machine) include:

Moderate size straight and helical toothed external

i h hi h d fi i hspur gears with high accuracy and finish

C tti th t th f d bl h li l h i b Cutting the teeth of double helical or herringbone

gears with a central recess (groove)gears with a central recess (groove)

Cutting teeth of straight or helical fluted cluster gearsCutting teeth of straight or helical fluted cluster gears

However this method needs, though automatic, few , g ,

indexing operations.

hGear shapingG h i i i il h k iGear shaping is similar to the rack type cutting process,excepting that, the linear type rack cutter is replaced by acircular cutter where both the cutter and the blankrotate as a pair of spur gears in addition to thep p greciprocation of the cutter.

hGear shapingG ti th d i h t i d b t ti i d iGeneration method is characterised by automatic indexingand ability of a single cutter to cover the entire range ofnumber of teeth for a given combination of module andnumber of teeth for a given combination of module andpressure angle and hence provides high productivity andeconomyeconomy.The gear type cutter is made of HSS and possesses properrake and clearance anglesrake and clearance angles.The additional advantages of gear shaping over rack typecutting are:cutting are:

Separate indexing is not required at allh h l l h f b h l d lStraight or helical teeth of both external and internal

spur gears can be produced with high accuracy andfi i hfinishProductivity is also higher.

bbGear HobbingThe HSS or carbide cutter having teeth like gear millingThe HSS or carbide cutter having teeth like gear millingcutter and the gear blank apparently interact like a pairof worm and wormwheelof worm and wormwheel.The hob (cutter) looks and behaves like a single ormultiple start wormsmultiple start worms.

(a) Straight (b) helical tooth and (c) worm wheel

bbGear HobbingHaving lesser number (only three) of tool – work

h bb h h dmotions, hobbing machines are much more rigid, strong

and productive than gear shaping machineand productive than gear shaping machine.

But hobbing provides lesser accuracy and finish and isBut hobbing provides lesser accuracy and finish and is

used only for cutting straight or helical teeth (single) ofy g g ( g )

external spur gears and worm wheels.

d f bbAdvantages of Gear Hobbing( ) Th h d i il d(a) The method is versatile and can generate spur,helical, worm and worm wheels.(b) Since gear hobbing is a continuous process, it israpid; economical and highly productiverapid; economical and highly productive.(c) The method produces accurate gears and is suitablef d d l b h dfor medium and large batch production.(d) The cutter is universal, because it can cut all gears of(d) e cutte s u ve sa , because t ca cut a gea s osame module, irrespective of number of teeth on thegeargear.

d f bbDisadvantages of gear Hobbing(a) Gear hobbing cannot generate internal gears andbevel gears.bevel gears.(b) Enough space has to be there in componentconfiguration for hob approach.

Applications of HobbingThe gears produced by gear hobbing are used in

automobiles, machine tools, various instruments, clocks

d h iand other equipments.

llMillingG t th b d d b b th di d d ill tGear teeth can be produced by both disc and end mill typeform milling cutter.

Fi ( ) di d d ill fFig. (a) disc type and end mill type for(b) single helical and(c) double helical teeth


llMillingP d ti f t th b f illi h t i dProduction of gear teeth by form milling are characterisedby:U f HSS f illiUse of HSS form milling cuttersUse of ordinary milling machinesLow production rate for⎯ Need of indexing after machining each tooth gapNeed of indexing after machining each tooth gap⎯ Slow speed and feedL d f fi i hLow accuracy and surface finishInventory problem – due to need of a set of eight cutters for

h d l l bi tieach module – pressure angle combinationEnd mill type cutters are used for teeth of large gears and / or

d lmodule.

h l d lShaping, Planning and SlottingS i h h d b d d i h iStraight toothed spur gear can be produced in shapingmachine.Both productivity and product quality are very low inthis process which therefore is used if at all for makingthis process which therefore, is used, if at all, for makingone or few teeth on one or two pieces of gears as andhen required for repair and maintenance purposewhen required for repair and maintenance purpose.

Planning and slotting machines work on the sameprinciple. Planning machine is used for making teeth oflarge gears whereas slotting for internal gears.large gears whereas slotting for internal gears.

Fig‐ gear teeth cutting in ordinary shaping machine

Fast production of teeth of spur gearsP ll l l i l hParallel multiple teethshapingIt is similar to ordinaryshaping but all the tooth gapsshaping but all the tooth gapsare made simultaneously,ithout requiring inde ingwithout requiring indexing,

by a set of radially in feedingl f lsingle point form tools.

This old process was highlyThis old process was highlyproductive but became almostobsolete for very high initialobsolete for very high initialand running costs.

Fast production of teeth of spur gearsB hiBroachingTeeth of small internal and external spur gears; straightp g ; gor single helical, of relatively softer materials areproduced in large quantity by broachingproduced in large quantity by broaching.This method leads to very high productivity and qualityb f h d b h h hbut cost of machine and broach are very high.

Manufacture of gears by rollingTh i h d h li l h f di d lThe straight and helical teeth of disc or rod type externalsteel gears of small to medium diameter and module aregenerated by cold rolling by either flat dies or circulardies.Such rolling imparts high accuracy and surface integrityof the teeth hich are formed b material flo unlikeof the teeth which are formed by material flow unlikecutting.Gear rolling is reasonably employed for high productivityand high quality though initial machinery costs areand high quality though initial machinery costs arerelatively high.L i f d b h t lli d thLarger size gears are formed by hot rolling and thenfinished by machining.

P d M llPowder MetallurgyS ll i hi h li l i l b lSmall size high quality external or internal spur, bevel orspiral gears are also produced by powder metallurgyprocess.Large size gears are rolled after briquetting and sinteringLarge size gears are rolled after briquetting and sinteringfor more strength and life.

d ll ll d d h dlPowder metallurgically produced gears hardly requireany further finishing work.

Wi EDMWire EDMG i ll b d l fi i h d i hGeometrically accurate but moderately finished straighttoothed metallic spur gears, both external and internaltype, can be produced by wire type Electro‐dischargeMachining (EDM).g ( )


Blanking in Press tool

Plastic moulding

Extrusion process

C iCastingS d iSand castingMetal mould castinggDie castingI iInvestment castingShell mould castinggCentrifugal casting

f hGear finishing process O f th l f th fi i hi i iOne of the goals of the gear finishing process in gears isto obtain a certain level of toughness in the gear teeth tod d/ li i t b di d t t f tireduce and/or eliminate bending and contact fatigue

failures.Reduction of index undulation errors associated withhelical gear teeth caused by the grinding process duringthe manufacture of the gears without degrading othergear accuracies (e.g. profile, tooth spacing) below levelsrequired for precision (AGMA16 or DIN1) gears.A mold of the space between several gear teeth isA mold of the space between several gear teeth isobtained, with the mold having a length equal to orgreater than the wavelength of the undulation error to begreater than the wavelength of the undulation error to bereduced.

A i fi i hi fil i ffi d h ld d hA micro finishing film is affixed to the mold and themold is placed relative to a gear tooth so that the microfinishing film rests against a tooth surface having theundulation error.The grit size of the micro finishing film is such as toremo e appro imatel 2 to 3 millionths of gear materialremove approximately 2 to 3 millionths of gear materialwith each pass through the teeth by the mold. Multiple

d b h d l h d lpasses are made by hand until the undulation error isreduced to an acceptable value. During the process thep g pmicro finishing film is replaced after approximately 3 or4 passes and the process is repeated for each tooth of the4 passes and the process is repeated for each tooth of thegear.

hGear shavingG h i i fi i hi ti ith hi hGear shaving is a gear finishing operation with highefficiency and high precision.When a work gear has been shaved by a shaving cutterwith a true involute profile, the ''mid‐concave''phenomena inevitably exist around the pitch points ofthe work gear tooth flanks.Aiming at this problem, a new‐style shaving cutter withunequal depth gashes is designed and manufactured.u equa dept gas es s des g ed a d a u actu ed.This paper analyses the forming of the gash on the basisof the slotting principle and proposes a gash‐designingof the slotting principle, and proposes a gash‐designingmethod.E i t h th t th h d h b ttExperiment has proven that the shaved gear has a bettersurface finish that achieves the anticipated effect.

b hGear burnishingIt is designed to remove or reduce gear tooth nicks and

burrs, along with improving the smoothness of the

tooth's active profile finish.

The action of the burnishing dies on the tooth surface

allows the machine to accomplish these quality

improvements without altering the tooth profile or lead.

Both internal and external gears are possible to burnish.

Gear LappingGear lapping is used to finish hardened gears by

ti ll i i fil h licorrecting small errors in spacing, profile, helix

angle and eccentricityangle, and eccentricity.

The operation is performed with all forms of gearsThe operation is performed with all forms of gears

running together with mating gears, and cast iron

toothed laps, under a flow of fine oil mixed with

an abrasive compound.

Ch‐8: Gear and Screw thread Manufacturing

Q. No Option Q. No Option1 A 8 D

B C2 B 9 C3 C 10 C3 C 10 C4 D 11 D4 D 11 D5 C 12 B56 A 13 D7 D

Screw Thread Screw Thread ManufacturingManufacturing

By S K MondalFor-2013 (IES, GATE & PSUs) Page 44

Processes, Machines and Tools ,Used For Producing Screw Threads (a) Machining( ) g

(b) Rolling( ) g

(c) Grindingg

Thread CuttingThread CuttingExternal InternalExternal Internal

• Threading on a latheh di l h

• Threading (on a lathe orl h )• Threading on a NC lathe

• With a die held in a stockNC lathe)• With a tap and holder

(manual)• With an automatic die

(manual NC, machine,semiautomatic, orWith an automatic die

(turret lathe or screwmachine) or NC lathe

semiautomatic, orautomatic)• With a collapsible tapmachine) or NC lathe

• BymillingB G i di

• With a collapsible tap(turret lathe, screw

hi i l• By Grinding machine, or specialthreading machine)•Bymilling

Th d C tti L thThread Cutting on LatheCan cut both external andCan cut both external andInternal threadh d fThread cutting is a form‐

cutting operation ang paccurately shaped tool isused (with zero rake)used (with zero rake)The lead screw and thelit t hi h idsplit nut, which provide

positive motion of thecarriage relative to therotation of the spindle.p

Cutting Threads with DiesStraight and tapered external threads can be cut quicklyStraight and tapered external threads can be cut quicklymanually by means of threading dies.Dies are made of carbon or high‐speed tool steel

( ) S lid h di di (b) lid dj bl h di di(a) Solid threading die; (b) solid‐adjustable threading die

h dThread TappingCutting internal thread by a multiple point tool is calledCutting internal thread by a multiple‐point tool is calledthread tapping, and the tool is called a tap.A hole of diameter slightly larger than the minordiameter of the thread must already exist.y

•The flutes on tap create cuttingd h h d f l dedges on the thread profile andprovide space for the chips andp p pthe passage of cutting fluid.•Taps are made of either carbon•Taps are made of either carbonor high‐speed steel and coatedwith TiN.

Thread MillingThread MillingHighly accurate threads,g yparticularly in largersizes, are often form‐sizes, are often formmilled. Either a single ora multiple form Cuttera multiple‐form Cuttermay be used.The milling cutter istilted at an angle equalg qto the helix angle of thethread and is fed inwardthread and is fed inwardradially to full depthwhile the work iswhile the work isstationary.

Thread GrindingGrinding can produceGrinding can producevery accurate threads, andit also permits threads toit also permits threads tobe produced in hardenedmaterialsmaterials.A single‐ribbed grindingwheel is employed butwheel is employed, butmultiple‐ribbed wheelsare used occasionallyare used occasionally.Centerless threadi di i d fgrinding is used for

making headless setsscrews.

Thread RollingThread rolling is used to produce threads in substantialThread rolling is used to produce threads in substantialquantities.Cold‐forming process operation in which the threads areformed by rolling a thread blank between hardened diesy gthat cause the metal to flow radially into the desiredshapeshape.Chip less process,fast and economical.Mechanical propertiesMechanical propertiesare good.

Sh Pl SlShaper, Planner, Slotter



hShaperTh l i i b h l d h k iThe relative motions between the tool and the workpiece,shaping and planing use a straight‐line cutting motion with a

l l fl fsingle‐point cutting tool to generate a flat surface.In shaping, the workpiece is fed at right angles to the cuttingp g, p g g gmotion between successive strokes of the tool.For either shaping or planing the tool is held in a clapper boxFor either shaping or planing, the tool is held in a clapper boxwhich prevents the cutting edge from being damaged on thereturn stroke of the toolreturn stroke of the tool.Relatively skilled workers are required to operate shapers andl d f h h h b d dplaners, and most of the shapes that can be produced on

them also can be made by much more productive processes,h ll b h dsuch as milling, broaching, or grinding.

hShaper Q i k t ti M h iQuick return motion Mechanism

k hQuick return motion MechanismI h i h i l i h ld i h lIn shaping, the cutting tool is held in the tool postlocated in the ram, which reciprocates over the workwith a forward stroke, cutting at velocity V and a quickreturn stroke at velocity VR.y R

The rpm rate of the drive crank (Ns) drives the ram anddetermines the elocit of the operationdetermines the velocity of the operation.

tti g t k glThe stroke ratio, = 0360s

cutting stroke angleR

Ram DriveRam DriveThe mechanical ram drive is a slotted arm quick return The mechanical ram drive is a slotted arm quick return motion mechanism,

Feed MechanismFeed MechanismTable feed is intermittent and is accomplished on theTable feed is intermittent and is accomplished on the

return (non cutting) stroke when the tool has cleared( g)

the workpiece.

The cross feed is given to the table with the help of a

cross feed screw which is actuated by a pawl which

engages a notched wheel (ratchet) keyed to the screwengages a notched wheel (ratchet) keyed to the screw.

l f f h hClassification of Shaper MachineSh hi l ll l ifi d Shapers, as machine tools usually are classified according to their general design features as follows,1. Horizontal

a Push cuta. Push‐cutb. Pull‐cut or draw cut shaper

2. VerticalR l l tta. Regular or slotters

b. Keyseatersy3. Special purpose

lFormula

Cutting speed, +=

(1 )1000

NL mV

Number of strokes,

1000

=swNf

,

Time of one stroke

s f+

=(1 ) minL mtTime of one stroke, = min

1000t

V(1 ) (1 )L m Lw m+ +Total time, (1 ) (1 ) min

1000 1000sL m Lw mT N

v vf+ +

= =

Hydraulic Shaper


Advantages of hydraulic shapingg y p g1. Cutting speed remains constant throughout most of the cuttingt k lik th k h h th d h ti lstroke, unlike the crank shaper where the speed changes continuously.

2. Since the power available remains constant throughout, it is possiblep g , pto utilise the full capacity of the cutting tool during the cutting stroke.

3 The ram reverses quickly without any shock due the hydraulic3. The ram reverses quickly without any shock due the hydrauliccylinder utilised. The inertia of the moving parts is relatively small.

Th d b f i k ibl l i l l4. The range and number of cutting strokes possible are relatively largein hydraulic shaper.

5. More strokes per minute can be achieved by consuming less time forreversal and return strokes.

PlPlanerPl i b d d h i l i lPlaning can be used to produce horizontal, vertical, orinclined flat surfaces on workpieces that are too large tobe accommodated on shapers.Planing is much less efficient than other basicPlaning is much less efficient than other basicmachining processes, such as milling, that will producesuch surfacessuch surfaces.Planing and planers have largely been replaced by planermilling machines or machines that can do both millingand planing.and planing.

SlSlotterSl i hi i b i ll i l i h ThSlotting machine is basically a vertical axis shaper. Thusthe workpieces, which cannot be conveniently held inshaper, can be machined in a slotter.Generally keyways splines serrations rectangularGenerally, keyways, splines, serrations, rectangulargrooves and similar shapes are machined in a slottingmachinemachine.The stroke of the ram is smaller in slotting machinesthan in shapers to account for the type of the work thatis handled in them.is handled in them.

Slotter SlotterTh f l d i l i ilThe types of tools used in a slotter are very similar tothose in a shaper, except that the cutting actually takesplace in the direction of cutting.However in view of the type of surfaces that are possibleHowever, in view of the type of surfaces that are possiblein the case of slotter, a large variety of boring bars orsingle point tools ith long shanks are usedsingle‐point tools with long shanks are used.

Ch‐5: Shaping and Planning

Q. No Option1 C

A2 A3 C3 C4 B45 B6 C

Grinding & FinishingG d g & s g


P FAbrasive Machining Processes

Process Features

Grinding Uses wheels accurate sizing finishing low MRR; Grinding Uses wheels, accurate sizing, finishing, low MRR; can be done at high speeds .

Creep feed Uses wheels with long cutting arc very slow feed Creep feed grinding

Uses wheels with long cutting arc, very slow feed rate and large depth of cut

Abrasive machining

High MRR, to obtain desired shapes and approximate sizes

Abrasive water jet Machining

Water jets with velocities up to 1000 m/sec carry abrasive particles (silica and garnet)j g p ( g )

Honing "Stones" containing fine abrasives; primarily a hole ‐ finishing processhole finishing process

Lapping Fine particles embedded in soft metal or cloth; primarily a surface‐finishing processprimarily a surface‐finishing process


G i diGrindingG i di i th t f f b iGrinding is the most common form of abrasivemachining.It is a material cutting process which engages an abrasivetool whose cutting elements are grains of abrasivematerial known as grit.These grits are characterized by sharp cutting points,g y p g p ,high hot hardness, and chemical stability and wearresistance.es sta ce.The grits are held together by a suitable bondingmaterial to give shape of an abrasive toolmaterial to give shape of an abrasive tool.Grinding can be compared with milling with an infinite

b f tti dnumber of cutting edge.

Fi tti ti f b i iFig- cutting action of abrasive grains

Why is high velocity desired in grinding?I i d i d ff h d ff f hi hIt is desired to off set the adverse effect of very highnegative rake angle of the working grit, to reduce theforce per grit as well as the overall grinding force.

Ad f G i diAdvantages of GrindingDimensional accuracy

Good surface finish

Good form and locational accuracy

Applicable to both hardened and unhardened material

A li i f G i diApplications of GrindingSurface finishing

Slitting and parting

Descaling, deburring

( )Stock removal (abrasive milling)

Fi i hi f fl ll li d i l fFinishing of flat as well as cylindrical surface

G i di f t l d tt d h i f th Grinding of tools and cutters and resharpening of the

samesame

dGrindingIf h b i i i i d i l h iIf each abrasive grain is viewed as a cutting tool then ingrinding operation.

HighRake angle can be positive zero or negative ranging fromRake angle can be positive, zero, or negative ranging from+45o to ‐60o, dull, rounded grits has large negative rake angleC i d i hi hCutting speed is very highVery high specific energy of cuttingy g p gy g

LowL h lLow shear angleLow feed rateLow depth of cut

Interaction of the grit with the workpieceG i i h f bl d hi i hGrit with favourable geometry can produce chip in shearmode.However, grits having large negative rake angle orrounded cutting edge do not form chips but may rub orrounded cutting edge do not form chips but may rub ormake a groove by ploughing leading to lateral flow of theorkpiece materialworkpiece material.

Fig‐ Grits engage shearing, ploughing and rubbing

How is chip accommodation volume is l t d t t i l l t ?related to material removal rate?

Volume of chip accommodation space ahead of each gritmust be greater than the chip volume produced by eachg p p ygrit to facilitate easy evacuation of the chip from thegrinding wheelgrinding wheel.

Specific energy consumption in grinding


G Ratioh d d f d h bThe grinding ratio or G ratio is defined as thee cubic mm

of stock removed divided by the cubic mm of wheel lost.

In conventional grinding the G ratio is in the range 20: 1In conventional grinding, the G ratio is in the range 20: 1to 80: 1.

The G ratio is a measure of grinding production andfl h f k h l d d i ireflects the amount of work a wheel can do during its

useful life.

As the wheel losses material it must be reset orAs the wheel losses material, it must be reset orrepositioned to maintain workpiece size.

Parameters for specify a grinding wheel ) Th f i i l1) The type of grit material2) The grit size) g3) The bond strength of the wheel, commonly knownas wheel hardnessas wheel hardness4) The structure of the wheel denoting the porosity i.e.the amount of inter grit spacing5) The type of bond material5) The type of bond material6) Other than these parameters, the wheel

f dd h d f dmanufacturer may add their own identification codeprefixing or suffixing (or both) the standard code.p g g

Abrasive Material

Comments and UsesMaterialAluminium oxide Softer and tougher than silicong

carbide; use on steel, iron, brass

Sili bid d f b bSilicon carbide Used for brass, bronze,aluminum, stainless steel andcast iron

cBN (cubic boron For grinding hard tough toolcBN (cubic boron nitride)

For grinding hard, tough toolsteels, stainless steel, cobalt andi k l b d ll dnickel based superalloys, and

hard coatingsDiamond Used to grind nonferrous

materials, tungsten carbide andmaterials, tungsten carbide andceramics

Why is aluminium oxide preferred to ili bid i i di t l?silicon carbide in grinding steel?

Al2O3 is tougher than SiC. Therefore it ispreferred to grind material having high tensilepreferred to grind material having high tensilestrength like steel. Moreover, Al2O3 shows higherh l h d l l dchemical inertness than SiC towards steel leadingto much improved wear resistance duringto much improved wear resistance duringgrinding.

G i iGrit sizeTh i i ff i l l d hThe grain size affects material removal rate and thesurface quality of workpiece in grinding.Large grit‐ big grinding capacity, rough workpiecesurfacesurfaceFine grit‐ small grinding capacity, smooth workpiece

fsurface

G dGradeTh i ll f h b d d kThe worn out grit must pull out from the bond and makeroom for fresh sharp grit in order to avoid excessive riseof grinding force and temperature.A soft wheel should be chosen for grinding hardA soft wheel should be chosen for grinding hardmaterial.

h d h l h ld b h f d fA hard wheel should be chosen for grinding softmaterial.

S / iStructure / concentrationTh h ld b f i di h lThe structure should be open for grinding wheelsengaged in high material removal to provide chipaccommodation space.The space between the grits also serves as pocket forThe space between the grits also serves as pocket forholding grinding fluid.

d h l d f l h l l fDense structured wheels are used for longer wheel life,for holding precision forms and profiles.

Why is coarse grain and open structured wheel f d f k l dis preferred for stock removal grinding?

Coarse grit allows large grit protrusion and openstructure provides large inter grit chip space. Thus inp g g p pcombination those two provide large space for chipaccommodation during stock removal grinding and riskaccommodation during stock removal grinding and riskof wheel loading is minimized.


Bonding Materials for Grinding wheelsT f B d A ibType of Bond Attributes

Vitrified bonds Composed of clays and other ceramicVitrified bonds Composed of clays and other ceramicsubstances, porous, strong, rigid, and

ff d b ilunaffected by oils, water, ortemperature. Brittle and can not be usedfor high wheel speed.

Resinoid or Plastic bond replaced shellac andResinoid, orphenolic

i

Plastic bond, replaced shellac andrubber wheels, not with alkalinei di fl idresins grinding fluid.

Shellac bond For flexible cut off wheels, replaced byp yresin bond.

Bonding Materials for Grinding wheelsBonding Materials for Grinding wheelsType of Bond AttributesType of Bond Attributes

Rubber bond For use in thin wheels, replaced by resin, p ybond.

O hl id Li it dOxychloridebond

Limited use.

Metal bond Extensively used with super abrasivewheels, high toughness, high accuracy,wheels, high toughness, high accuracy,large stock removal.

El t l t d U d f ll h l f h l dElectroplatedbond

Used for small wheel, form wheel andthin super abrasive wheels, for abrasivemilling and ultra high speed grinding.Replace by electroplated bond

lGlazingWi h i i di h l b d ll i hWith continuous use a grinding wheel becomes dull withthe sharp abrasive grains becoming rounded.This condition of a dull grinding wheel with worn outgrains is termed as glazinggrains is termed as glazing.

dLoadingS i di hi l d d i h bSome grinding chips get lodged into the spaces betweenthe grits resulting in a condition known as loaded wheel.Loading is generally caused during the grinding of softand ductile materialsand ductile materials.A loaded grinding wheel cannot cut properly and needddressing.

D iDressingD i i h di i i f h h l f hi hDressing is the conditioning of the wheel surface whichensures that grit cutting edges are exposed from thebond and thus able to penetrate into the workpiecematerial.In dressing attempts are made to splinter the abrasivegrains to make them sharp and free cutting and also tograins to make them sharp and free cutting and also toremove any residue left by material being ground.Dressing therefore produces micro‐geometry.

T iTruingT i i h f i h i dTruing is the act of regenerating the required geometryon the grinding wheel.Truing is also required on a new conventional wheel toensure concentricity with specific mounting systemensure concentricity with specific mounting system.Truing and dressing are commonly combined into one

f l b d h l boperation for conventional abrasive grinding wheels, butare usually two distinctly separate operation for superabrasive wheel.

Balancing Grinding WheelsBecause of the high rotation speeds involved, grindingwheels must never be used unless they are in goody gbalance.Grinding wheel must be balanced Statically andGrinding wheel must be balanced Statically andDynamically.A slight imbalance will produce vibrations that will causewaviness in the work surface. It may cause a wheel toybreak, with the probability of serious damage and injury.

C f d i diCreep feed grindingThi hi bl i l i di f f This machine enables single pass grinding of a surface with a larger down feed but slower table speed than that adopted for multi‐pass conventional surface grinding. In creep‐feed grinding the entire depth of cut is In creep feed grinding, the entire depth of cut is completed in one pass only using very small in‐feed ratesrates.

State the basic advantage of a creep feed i d ti l fgrinder over a conventional surface

Productivity is enhanced and life of the grinding wheel is extended.


l d l dCylindrical GrindingC li d i l i di i l d fCenter‐type cylindrical grinding is commonly used farproducing external cylindrical surfaces.The grinding wheel revolves at an ordinary cuttingspeed and the workpiece rotates on centers at a muchspeed, and the workpiece rotates on centers at a muchslower speed.G d h l bl h h h kGrinding machines are available in which the workpieceis held in a chuck for grinding both external and internalcylindrical surfaces.

l dCenterless GrindingC l i di k i ibl i d b hCenterless grinding makes it possible to grind bothexternal and internal cylindrical surfaces withoutrequiring the workpiece to be mounted between centersor in a chuck.This eliminates the requirement of center holes in someorkpieces and the necessit for mounting theworkpieces and the necessity for mounting the

workpiece, thereby reducing the cycle time.Two wheels are used. The larger one operates at regulargrinding speeds and does the actual grinding. Thegrinding speeds and does the actual grinding. Thesmaller wheel is the regulating wheel. It is mounted atan angle to the plane of the grinding wheelan angle to the plane of the grinding wheel.

l dCenterless GrindingTh l i h l l h i dThe regulating wheel controls the rotation andlongitudinal motion of the workpiece and usually is aplastic‐ or rubber‐bonded wheel with a fairly wide face.The workpiece is held against the work‐rest blade by the The workpiece is held against the work rest blade by the cutting forces exerted by the grinding wheel and rotates at appro imatel the same surface speed as that of the at approximately the same surface speed as that of the regulating wheel.

Centerless Grindingl dCenterless Grinding

The axial feed is calculated by the equationF = dN sinπ θF = dN sinwhere

π θ

F = feed (mm/min)d di f h l i h l ( )d = diameter of the regulating wheel (mm)N = revolutions per minute of the regulating wheelN evo u o s pe u e o e egu a g w ee

= angle of inclination of the θ regulating wheel

l l dCentreless internal GrindingThi hi i d f i di li d i l dThis machine is used for grinding cylindrical andtapered holes in cylindrical parts (e.g. cylindrical liners,various bushings etc).The workpiece is rotated between supporting rollThe workpiece is rotated between supporting roll,pressure roll and regulating wheel and is ground by thegrinding heelgrinding wheel.

State the disadvantages of centrelessli d i l i di hi ?cylindrical grinding machine?

• It does not grind concentrically with centres.• Large diameter short workpiece are difficult to Large diameter short workpiece are difficult to

control in the processI i k i di l i• It may not improve workpiece perpendicularity.

Surface Grinding MachinesSurface grinding machines are used primarily togrind flat surfaces.gHowever formed, irregular surfaces can beproduced on some types of surface grinders by useproduced on some types of surface grinders by useof a formed wheel.

Four basic types of surface grinding machines are:Four basic types of surface grinding machines are:1. Horizontal spindle and reciprocating table2. Vertical spindle and reciprocating table3. Horizontal spindle and rotary table3. Horizontal spindle and rotary table4. Vertical spindle and rotary table


LappingL i i b i ll b i i hi h l Lapping is basically an abrasive process in which loose abrasives function as cutting points finding momentary support from the laps. Material removal in lapping usually ranges from 003 to Material removal in lapping usually ranges from .003 to .03 mm but many reach 0.08 to 0.1mm in certain cases.

h f lCharacteristics of lapping processU f l b i b l d h k iUse of loose abrasive between lap and the workpieceUsually lap and workpiece are not positively driven but y p p p yare guided in contact with each otherRelative motion between the lap and the work should Relative motion between the lap and the work should change continuously so that path of the abrasive grains f h l d h kof the lap is not repeated on the workpiece.

Cast iron is the mostly used lap material. However, soft Cast o s t e ost y used ap ate a . o eve , so tsteel, copper, brass, hardwood as well as hardened steel and glass are also usedand glass are also used.

b f lAbrasives of lappingAl2O3 and SiC, grain size 5 ~100 μm

Cr2O3, grain size 1 ~ 2 μm

B4C3, grain size 5 ‐ 60 μm

Diamond, grain size 0.5 ~ 5 μm

h l l f lVehicle materials for lappingMachine oil

Rapeside oil

grease

Technical parameters affecting lapping processes are

unit pressure

the grain size of abrasive

concentration of abrasive in the vehicle

lapping speed

HoningH i i fi i hi i hi h l ll d hHoning is a finishing process, in which a tool called honecarries out a combined rotary and reciprocating motionwhile the workpiece does not perform any workingmotion.Most honing is done on internal cylindrical surface, suchas automobile c lindrical alls The honing stones areas automobile cylindrical walls. The honing stones areheld against the workpiece with controlled light

h h h d d d ll bpressure. The honing head is not guided externally but,instead, floats in the hole, being guided by the workg g ysurface.

HoningI i d i d hIt is desired that

1. Honing stones should not leave the work surfaceg2. Stroke length must cover the entire work length.

I h i d ill i3. In honing rotary and oscillatory motions arecombined to produce a cross hatched lay pattern.

The honing stones are given a complex motion so asg g pto prevent every single grit from repeating its pathover the work surface.over the work surface.

Honing

Fig. Honing tool Fig. Lay pattern produced by combination of rotary and oscillatory motionoscillatory motion


The critical process parameters are1. rotation speed

2. oscillation speed

3. length and position of the stroke

4. honing stick pressure

B ffiBuffingB ffi i li hi ti i hi h th k iBuffing is a polishing operation in which the workpieceis brought into contact with a revolving cloth wheel thath b h d ith fi b i h li hihas been charged with a fine abrasive, such as polishingrough.The wheels are made of disks of linen, cotton,broadcloth, or canvas, and achieve the desired degree offirmness through the amount of stitching used to fastenthe layers of cloth together.Negligible amount of material is removed in buffingwhile a very high luster is generated on the buffedwhile a very high luster is generated on the buffedsurface.The dimensional accuracy of the parts is not affected byThe dimensional accuracy of the parts is not affected bythe buffing operation.

hSuper Finishing

Fig. super finishing of end faceof a cylindrical work piece in radial mode

In this both feeding and oscillation of the superIn this both feeding and oscillation of the superfinishing stone is given in the radial direction.

Super Finishing

Fi fi i hi ti i l dFig. super finishing operation in plunge mode

In this case the abrasive stone covers the section of theworkpiece requiring super finish. The abrasive stone isslowly fed in radial direction while its oscillation isslowly fed in radial direction while its oscillation isimparted in the axial direction. It reduce surfaceroughness and increase bearing load capacityroughness and increase bearing load capacity.

State the specific application of a planetary i t l i dinternal grinder.

Planetary internal grinders find application for grindinga eta y te a g de s d app cat o o g d gholes in workpieces of irregular shape or large heavyworkpiecesworkpieces.

Ch‐9: GrindingQ. No Option Q. No Option1 D 7 A

D A2 D 8 A3 A 9 A3 A 9 A4 A 10 C4 A 10 C5 B 11 A56 B 12 D


LatheLathe


IES ‐ 2001Th i dl d i l l h The spindle speed range in a general purpose lathe is divided into steps which approximately follow(a) Arithmetic progression (b) Geometric progression(b) Geometric progression(c) Harmonic progression (d) Logarithmic progression

B

IES ‐ 1992F d b f i l h i d i d Feed gear box for a screw cutting lathe is designed on the basis of(a) Geometric progression(b) Arithmetic progression (b) Arithmetic progression (c) Harmonic progression(d) None.

A

IES ‐ 1998A i l h d f i h i b d dA single start thread of pitch 2 mm is to be producedon a lathe having a lead screw with a double startthread of pitch 4 mm. The ratio of speeds betweenthe spindle and lead screw for this operation isp p(a) 1 : 2 (b) 2: 1( ) (d)(c) 1: 4 (d) 4: 1

D

IES – 1993, ISRO‐2009I i i d h d f i hIt is required to cut screw threads of 2 mm pitch ona lathe. The lead screw has a pitch of 6 mm. If thespindle speed is 60 rpm, then the speed of the leadscrewwill be(a) 10 rpm (b) 20 rpm( ) (d)(c) 120 rpm (d) 180 rpm

B

ExampleHow much machining time will be required to reduce

the diameter of a cast iron rod from 120 mm to 116 mm

l h f b i i bidover a length of 100 mm by turning using a carbide

insert Cutting velocity is 100 m/min and feed rate = 0 2insert. Cutting velocity is 100 m/min and feed rate = 0.2

mm/rev./

IES 2010I t i lid d b if th t lIn turning a solid round bar, if the travelof the cutting tool in the direction ofof the cutting tool in the direction offeed motion is 1000 mm, rotationalspeed of the workpiece is 500 rpm, andrate of feed is 0 2 mm/revolution thenrate of feed is 0.2 mm/revolution, thenthemachining timewill beg(a) 10 seconds (b) 100 seconds(c) 5 minutes (d) 10 minutes

D

IES ‐ 2003Th i k f k i fThe time taken to face a workpiece of 72 mmdiameter, if the spindle speed is 80 r.p.m. and cross‐feed is 0.3 mm/rev, is(a) 1 5 minutes (b) 3 0 minutes(a) 1.5 minutes (b) 3.0 minutes(c) 5.4 minutes(d) 8.5 minutes

AA

IAS ‐ 2002A l di i l lA 150 mm long, 12 mm diameter 304 stainless steelrod is being reduced in diameter to 11∙5 mm byturning on a lathe. The spindle rotates at N = 400rpm and the tool is travelling at an axial speed ofp g p200 mm/min. The time taken for cutting is given by(a) 30 s (b) 36 s(a) 30 s (b) 36 s(c) 1 minute (d) 45 s

DD


IES ‐ 2004A di b l k i i dA medium carbon steel workpiece is turned on alathe at 50 m/min. cutting speed 0.8 mm/rev feedand 1.5 mm depth of cut. What is the rate of metalremoval?(a) 1000 mm3/min(b) /(b) 60,000 mm3/min(c) 20,000 mm3/min(c) 0,000 /(d) Can not be calculated with the given data

B

IES ‐ 2006F i l h h h d fFor taper turning on centre lathes, the method ofswiveling the compound rest is preferred for:(a) Long jobs with small taper angles(b) Long jobs with steep taper angles(b) Long jobs with steep taper angles(c) Short jobs with small taper angles(d) Short jobs with steep taper angles

DD

lExampleFi d h l hi h h d h ldFind the angle at which the compound rest shouldbe set up to turn taper on the workpiece having alength of 200 mm, larger diameter 45 mm and thesmaller 30 mm.3

IES ‐ 1992T il k h d f i i Tail stock set over method of taper turning is preferred for(a) Internal tapers(b) Small tapers(b) Small tapers(c) Long slender tapers(d) Steep tapers

CC

IAS ‐ 2002Th f ff f il k f iThe amount of offset of tail stock for turning taperon full length of a job 300 mm long which is to haveits two diameters at 50 mm and 38 mm respectivelyis(a) 6 mm (b) 12 mm( ) (d)(c) 25 mm (d) 44 mm

A

IES ‐ 1998A l h f h dA 400 mm long shaft has a 100 mm tapered step atthe middle with 4° included angle. The tailstockoffset required to produce this taper on a lathewould be(a) 400 sin 4° (b) 400 sin 2°( ) (d)(c) 100 sin 4° (d) 100 sin 2°

B

IES 2010The effect of centering errorThe effect of centering errorwhen the tool is set above thecenter line as shown in the figurecenter line as shown in the figureresults effectively in

1 Increase in rake angle1. Increase in rake angle.2. Reduction in rake angle.3. Increase in clearance angle.4. Reduction in clearance angle.Which of these statements is/arecorrect?

(a) 1 only (b) 1 and 4 only(c) 2 and 4 only (d) 1 2 3 and 4(c) 2 and 4 only (d) 1, 2, 3 and 4B

IES ‐ 2012L h hi i h k i fLathe machine with turret can turn a work piece oflimited length only because,(a) Cross slide motion is obstructed by turret(b) Turret cannot work on a long job(b) Turret cannot work on a long job(c) Chuck cannot be replaced by a face plate(d) Turret replaces the loose centre

BB

GATE ‐ 2002A lead‐screw with half nuts in a lathe, free to rotate

b h d hin both directions has

( ) V h d(a) V‐threads

(b) Whit th th d(b) Whitworth threads

(c) Buttress threads(c) Buttress threads

(d) ACME threads(d) ACME threads

DD


GATE – 2008 Th fi h i l h i fThe figure shows an incomplete schematic of aconventional lathe to be used for cutting threadswith different pitches. The speed gear box Uv, isshown and the feed gear box Us, is to be placed. P, Q.g s, p , QR and S denote locations and have no othersignificance Changes in U should NOT affect thesignificance. Changes in Uv, should NOT affect thepitch of the thread being cut and changes in Us,h ld NOT ff t th tti dshould NOT affect the cutting speed.

C tdContd…..

GATE ‐2008 Contd….

Th i d h l f U The correct connections and the correct placement of Us are given by( ) Q d E t d U i l d b t P d Q(a) Q and E are connected. Us, is placed between P and Q.(b) S and E are connected. Us is placed between R and S.( ) Q d E d U i l d b Q d E(c) Q and E are connected. Us, is placed between Q and E.(d) S and E are connected. Us, is placed between S and E.

C

IES ‐ 2004M h Li I (C i l ) i h Li II (F )Match List I (Cutting tools) with List II (Features)and select the correct answer using the codes givenbelow the Lists:

List I List IIList I List IIA. Turning tool 1. Chisel edgeB. Reamer 2. FlutesC Milling cutter 3 Axial reliefC. Milling cutter 3. Axial relief

4. Side relief CCodes: A B C A B C

(a) 1 2 3 (b) 4 3 2(a) 1 2 3 (b) 4 3 2(c) 4 2 3 (d) 1 3 2

GATE‐1994T d f fi i h d j bTo get good surface finish on a turned job,one should use a sharp tool with a …..feedone should use a sharp tool with a …..feedand…… speed of rotation of the job.

( )(a) Minimum, minimum(b) Minimum maximum(b) Minimum, maximum(c) Maximum, maximum( ) ,(d) Maximum, minimum B

IES ‐ 1996I i f l d d i i k In turning of slender rods, it is necessary to keep the transverse force minimum mainly to(a) Improve the surface finish(b) Increase productivity(b) Increase productivity(c) Improve cutting efficiency (d) Reduce vibrations and chatter. D

IES ‐ 2009Wh i h b f j i lf d h k?What is the number of jaws in self‐centred chuck?(a) Eight( ) g(b) Six( ) F(c) Four(d) Three D( )

IES ‐ 1999Whi h f h f ll i f fWhich one of the following sets of forces areencountered by a lathe parting tool while groovecutting?(a) Tangential radial and axial(a) Tangential, radial and axial(b) Tangential and radial(c) Tangential and axial(d) Radial and axial A(d) Radial and axial A

IES ‐ 2009Whi h f h f ll i h d h ld b d Which one of the following methods should be used for turning internal taper only?(a) Tailstock offset(b) Taper attachment(b) Taper attachment(c) Form tool(d) Compound rest

DD

IES ‐ 1992Whi h f h f ll i i i i h Which of the following statement is incorrect with reference of lathe cutting tools?(a) The flank of the tool is the surface below and adjacent to the cutting edgesadjacent to the cutting edges(b) The nose is the corner, or chamfer joining the side

d h d dcutting and the end cutting edges(c) The heel is that part of the which is shaped to (c) e ee s t at pa t o t e c s s aped toproduce the cutting edges and face(d) Th b i th t f f th h k hi h i t (d) The base is that surface of the shank which against the support and takes tangent

CFor-2013 (IES, GATE & PSUs) Page 56

IES ‐ 2006I i i d h d i h d blIt is required to cut screw threads with double startand 2 mm pitch on a lathe having lead screw pitchof 6 mm. What is the speed ratio between lathespindle and lead screw?p(a) 1 : 3 (b) 3: 1( ) (d)(c) 2 : 3 (d) 3: 2

D

IES ‐ 1997C id h f ll i iConsider the following operations:1. Under cutting 2. Plain turningg g3. Taper turning 4. Thread cuttingTh f h i i hi iThe correct sequence of these operations in machining aproduct is(a) 2, 3, 4, 1 (b) 3, 2, 4, 1( ) (d)(c) 2, 3, 1, 4 (d) 3, 2, 1, 4

C

IES ‐ 2009A l h i d d i b hA capstan lathe is used to mass‐produce, in batchesof 200, a particular component. The direct materialcost is Rs 4 per piece, the direct labour cost is Rs 3per piece and the overhead costs are 400% of thep p 4labour costs. What is the production cost per piece?(a) Rs 19 (b) Rs 23(a) Rs 19 (b) Rs 23(c) Rs 16 (d) Rs 15

A

IES ‐ 2007A i (A) I l i i dl i l h hAssertion (A): In a multi‐spindle automatic lathe, theturret tool holder is indexed to engage the cutting tools

b f hone by one for successive machining operations.Reason (R): Turret is a multiple tool holder so that for( ) psuccessive machining operation, the tools need not bechanged.g(a) Both A and R are individually true and R is the correctexplanation of Aexplanation of A(b) Both A and R are individually true but R is not the

l i f Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true A

IES ‐ 1995C id th f ll i h t i tiConsider the following characteristics:1. Multiple operations can be performed2. Operator's fatigue is greatly reduced.3 Ideally suited for batch production3. Ideally suited for batch production4. A break‐down in one machine does not affect theflo of productsflow of products.5. Can accommodate modifications in design of

h lcomponents, within certain limits.The characteristics which can be attributed to specialppurpose machines would include(a) 1 3 and 4 (b) 1 2 and 4(a) 1, 3 and 4 (b) 1, 2 and 4(c) 2, 3 and 5 (d) 1, 2 and 5 C

IES ‐ 1996A i (A) S i l hi l dAssertion (A): Special purpose machine tools andautomatic machine tools are quite useful for jobshopsReason (R): Special purpose machine tools can doReason (R): Special purpose machine tools can dospecial types of machining work automatically( ) h d d d ll d h(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true D

IES ‐ 2003Whi h f h f ll i h i iWhich one of the following mechanisms isemployed for indexing of turret in an automaticlathe?(a) Whitworth (b) Rack and pinion(a) Whitworth (b) Rack and pinion(c) Ratchet and pawl (d) Geneva wheel

CC

IES ‐ 2009F h f f fFor the manufacture of screw fasteners on a massscale, which is themost suitablemachine tool?(a) Capstan lathe(b) Single spindle automatic lathe(b) Single‐spindle automatic lathe(c) CNC turning centre (lathe)(d) CNC machining centre

B

IES ‐ 2001Th i d i f h i i l i dlThe indexing of the turret in a single‐spindleautomatic lathe is done using(a) Geneva mechanism(b) Ratchet and Pawl mechanism(b) Ratchet and Pawl mechanism(c) Rack and pinion mechanism(d) Whitworth mechanism

B


IES ‐ 1995A ti (A) I S i t t ti l th thAssertion (A): In a Swiss ‐ type automatic lathe, theturret is given longitudinal feed for each tool in a

ifi d ith it bl i d ispecific orderwith suitable indexing.Reason (R): A turret is a multiple tool holder tofacilitate machining with each tool by indexingwithout the need to change the tools.(a) Both A and R are individually true and R is thecorrect explanation of Aco ect e p a at o o(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false( )(d) A is false but R is true D

IES ‐ 1992M i d i f ll d l d iMaximum production of small and slender parts isdone by(a) Watch maker's lathe(b) Sliding head stock automatic lathe(b) Sliding head stock automatic lathe(c) Multi‐spindle automatic lathe(d) Capstan lathe

C

IAS ‐ 2007Whi h f h f ll i i h h i i fWhich one of the following is the characteristic forcapstan lathe?(a) Rate of production is low(b) Labour cost is high(b) Labour cost is high(c) Used for handling jobs of varying shapes and sizes(d) Capstan head is mounted on a slide

D

IAS ‐ 2002C id h f ll i l d TConsider the following statements related to Turretlathe:1. Turret is mounted directly on the saddle.2 Turret is mounted on an auxiliary slide2. Turret is mounted on an auxiliary slide.3. Much heavier and larger jobs than Capstan lathe canbe produced.Which of the above statements is/are correct?Which of the above statements is/are correct?(a) 1 and 3 (b) 2 and 3(c) 1 only (d) 2 only A

IAS ‐ 1996A f h l h l ( ) iApart from hexagonal turret, the elements (s) in aturret lathe include (s)(a) Cross‐slide tool post(b) Cross slide tool post and rear tool post(b) Cross‐slide tool post and rear tool post(c) Cross‐slide tool post and tail stock(d) Teal tool post and tail stock

AA

IAS ‐ 2004S i hi hSwiss type screwmachines have(a) Turrets (b) Radial slides( ) ( )(c) Spindle carriers (d) Tool posts

C

IAS ‐ 2001C id h f ll i i d iConsider the following operations and timerequired on a multi spindle automatic machine toproduce a particular job1 Turning 1 2 minutes1. Turning …1.2 minutes2. Drilling …1.6 minutes3. Forming …0.2 minute4 Parting 0 6 minute4. Parting …0.6 minuteThe time required to make one piece (cycle time) will be(a) 0.6 minutes (b) 1.6 minutes(c) 3 6 minutes (d) 0 9 minute(c) 3.6 minutes (d) 0.9 minute

B

IAS ‐ 1995A ti (A) I lti i dl t t th t tAssertion (A): In amulti‐spindle automat, the turretis indexed to engage each of the cutting tool

t d itmounted on it.Reason(R): Turret is a multiple tool holder so thatthe machining can be continued with each toolwithout the need to change the tool.(a) Both A and R are individually true and R is thecorrect explanation of Aco ect e p a at o o(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false( )(d) A is false but R is true D

IAS ‐ 1994A l i i dl f f iA multi‐spindle automat performs four operationswith times 50, 60, 65 and 75 seconds at each of itswork centers. The cycle time (time required tomanufacture onework piece) in secondswill bep )(a) 50 + 60 + 65 + 75(b) ( ) /(b) (50 + 60 + 65 + 75) /4(c) 75/4(c) 75/4(d) 75

D


IAS ‐ 1998A i (A) F h d i h i dl dAssertion (A): For thread cutting, the spindle speedselected on a lathe, is very low.Reason (R): The required feed rate is low inthreading operationthreading operation.(a) Both A and R are individually true and R is the

l fcorrect explanation of A(b) Both A and R are individually true but R is not the(b) ot a d R a e d v dua y t ue but R s ot t ecorrect explanation of A( ) A i t b t R i f l(c) A is true but R is false(d) A is false but R is true C

IAS ‐ 1998C id h f ll i i d i hConsider the following statements associated withthe lathe accessories:1. Steady rest is used for supporting a long job inbetween head stock and tail stockbetween head stock and tail stock.2. Mandrel is used for turning small cylindrical job.3. Collects are used for turning disc‐shaped job.Of these statements:Of these statements:(a) 1 and 2 are correct (b) 2 and 3 are correct(c) 3 alone is correct (d) 1 alone is correct

DD

IES 2011f d b f h hIn Norton type feed gearbox for cutting Whitworth

standard threads with a standard TPI Leadscrew, powerflows from:(a) Spindle to Tumbler gear to Norton cone to Meander( ) p gdrive to Leadscrew(b) Spindle to Norton cone to Tumbler geat to Meander(b) Spindle to Norton cone to Tumbler geat to Meanderdrive to Leadscrew(c) Spindle t o Tumbler gear to Meander drive to Norton(c) Spindle t o Tumbler gear to Meander drive to Nortoncone to Leadscrew(d) dl d d bl(d) Spindle to Norton cone to Meander drive to Tumblergear to Leadscrew A

IAS ‐ 2000C id h f ll i fConsider the following features:1. All spindles operate simultaneously,p p y,2. One piece is completed each time the tools arewithdrawn and the spindles are indexedwithdrawn and the spindles are indexed3. The tool slide indexes or revolves with the spindlecarrierWhich of these features are characteristics of a multi‐Which of these features are characteristics of a multi‐spindle automatic machine used for bar work?( ) d (b) d(a) 1, 2 and 3 (b) 1 and 2(c) 2 and 3 (d) 1 and 3 A(c) 2 and 3 (d) 1 and 3 A

DrillingDrilling

B S K M d lBy S K Mondal

IES ‐ 2004C id h f ll iConsider the following statements:The helical flute in a twist drill provides the necessaryp y1. Clearance angle for the cutting edge

R k l f h i d2. Rake angle for the cutting edge3. Space for the chip to come out during drilling3 p p g g4. Guidance for the drill to enter into the workpieceh h f h bWhich of the statements given above are correct?

(a) 1 and 2 (b) 2 and 3(a) 1 and 2 (b) 2 and 3(c) 3 and 4 (d) 1 and 4

B

IES ‐ 2003Th f h li l i i d ill iThe purpose of helical grooves in a twist drill is to1. Improve the stiffnessp2. Save a tool material

P id f hi l3. Provide space for chip removal4. Provide rake angle for the cutting edge4 g g gSelect the correct answer using the codes given below:

dCodes:(a) 1 and 2 (b) 2 and 3(a) 1 and 2 (b) 2 and 3(c) 3 and 4 (d) 1 and 4

C

GATE‐ 1996Th k l i d illThe rake angle in a drill(a) Increases from centre to periphery( ) p p y(b) decreases from centre to periphery( ) R i(c) Remains constant(d) Is irrelevant to the drilling operation( ) g p

A

IES ‐ 1997Th k l i i d illThe rake angle in a twist drill(a) Varies from minimum near the dead centre to a( )maximum value at the periphery(b) Is maximum at the dead centre and zero at the(b) Is maximum at the dead centre and zero at theperiphery(c) Is constant at every point of the cutting edge(d) Is a function of the size of the chisel edge(d) Is a function of the size of the chisel edge.

A


IES ‐ 1992A d ill f d illi d h l i l i h ldA drill for drilling deep holes in aluminum shouldhave(a) High helix angle (b) Taper shank(c) Small point angle (d) No lip(c) Small point angle (d) No lip

A

GATE‐ 1997H li l f f h li d ill i llHelix angle of fast helix drill is normally(a) 35o( ) 35(b) 60o

( )(c) 90o

(d) 5o( ) 5A

IES ‐ 1992L h li l d ill f d f d illiLow helix angle drills are preferred for drillingholes in(a) Plastics (b) Copper(c) Cast steel (d) Carbon steel(c) Cast steel (d) Carbon steel

D

IFS‐2011IFS‐2011Discuss deep hole drilling keeping in mind speed andDiscuss deep‐hole drilling keeping in mind speed and

feed, mentioning the technique of applying coolant., g q pp y g

[5‐marks]

lExampleA hole with 40‐mm diameter and 50‐mm depth is to

b d ll d ld l hbe drilled in mild steel component. The cutting

speed can be taken as 65 m/min and the feed rate asspeed can be taken as 65 m/min and the feed rate as

0.25 mm/rev. Calculate the machining time and the0.25 mm/rev. Calculate the machining time and the

material removal rate.

GATE‐ 2002Th i k d ill h l h h hi kThe time taken to drill a hole through a 25 mm thickplate with the drill rotating at 300 r.p.m. andmoving at a feed rate of 0.25 mm/revolution is(a) 10 sec (b) 20 sec(a) 10 sec (b) 20 sec(c) 60 sec (d) 100 sec

B

GATE‐ 2004Th h h l f di b d ill dThrough holes of 10 mm diameter are to be drilledin a steel plate of 20 mm thickness. Drill spindlespeed is 300 rpm, feed 0.2 mm/ rev and drill pointangle is 120°. Assuming drill over travel of 2 mm, theg g ,time for producing a hole will be(a) 4 seconds (b) 2 seconds(a) 4 seconds (b) 25 seconds(c) 100 seconds (d) 110 seconds

B

GATE‐ 2012In a single pass drilling operation, a through hole of

d b d ll d l l f15 mm diameter is to be drilled in a steel plate of 50

mm thickness Drill spindle speed is 500 rpm feedmm thickness. Drill spindle speed is 500 rpm, feed

is 0.2 mm/rev and drill point angle is 118°. Assumingis 0.2 mm/rev and drill point angle is 118 . Assuming

2 mm clearance at approach and exit, the total drill

time (in seconds) is

(a) 35.1 (b) 32.4

(c) 31.2 (d) 30.1

IES ‐ 2002Th f di l d illi hi i b i i dThe arm of a radial drilling machine is being raisedat a speed of 3.9 m/min by single start squarethreads of 6 mm pitch and 30 mm diameter. Thespeed of the screwp(a) Is 650 rpm(b)(b) Is 180 rpm(c) Is 130 rpm(c) s 30 p(d) Cannot be determined as the data is insufficient

A


IES ‐ 1994Th i b i i dl dThe ratio between two consecutive spindle speedsfor a six‐speed drilling machine using drills ofdiameter 6.25 to 25 mm size and at a cutting velocityof 18 m/min is/(a) 1.02 (b) 1.32( ) (d)(c) 1.62 (d) 1.82

B

IES ‐ 2009Wh i h d illi i f d i h l iWhat is the drilling time for producing a hole in anMS sheet of 25 mm thickness using an HSS drill of20 mm diameter? The cutting speed and feed fordrill are 20 m/min and 0.25 mm/revolution/ 5 /respectively, Neglect time taken for setting up,approaching and travelling of toolsapproaching and travelling of tools.(a) 0.314 min (b) 0.236 min(c) 0.438 min (d) 0.443 min

AA

IES ‐ 2002A 8 H S S d ill i d d ill h l iA 31.8 mm H.S.S. drill is used to drill a hole in a castiron block 100 mm thick at a cutting speed 20m/min and feed 0.3 mm/rev. If the over travel ofdrill is 4 mm and approach 9 mm, the time required4 pp 9 , qto drill the hole is(a) 1 min 40 s (b) 1 min 44 s(a) 1 min 40 s (b) 1 min 44 s(c) 1 min 49 s (d) 1 min 53 s

D

IAS ‐ 1999T d ill di h l h hTo drill a 10 mm diameter hole through a 20 mmthick M.S. plate with a drill bit running at 300 rpmand a feed of 0.25 mm per revolution, time takenwill be(a) 8 s (b) 16 s( ) (d)(c) 24 s (d) 32 s

B

( ) k dGATE – 2007 (PI) Linked S‐1Bli d h l di t dBlind holes 10 mm diameter, 50 mm deep arebeing drilled in steel block. Drilling spindleg g pspeed is 600 rpm, feed 0.2 mm/rev, point angle ofdrill is 120odrill is 120o.Machining time (in minutes) per hole will beg ( ) p(a) 0.08 (b) 0.31 (c) 0.44 (d) 0.86

C

( ) k dGATE – 2007 (PI) Linked S‐2Bli d h l di t dBlind holes 10 mm diameter, 50 mm deep arebeing drilled in steel block. Drilling spindleg g pspeed is 600 rpm, feed 0.2 mm/rev, point angle ofdrill is 120odrill is 120o.During the above operation, the drill wears outg p ,after producing 200 holes. Taylor’s tool lifeequation is of the form VT0 3 C where Vequation is of the form VT0.3 = C, where V =cutting speed in m/minute and T = tool life ingminutes. Taylor’s constant C will be( ) (b) ( ) (d)(a) 15 (b) 72 (c) 93 (d) 490B

IAS ‐ 1994Th i (i i ) f d illi h l i i bThe time (in minutes) for drilling a hole is given by

hholetheofDepth +

h 'h' i hRPMFeed

hholetheofDeptht×

+=

where 'h' is the(a) Length of the drill( ) g(b) Drill diameter( ) l l h f h d ll(c) Flute length of the drill(d) Cone height of the drill.(d) Cone height of the drill.

D

IES ‐ 1999M t h Li t I (D ill bit ) ith Li t II (A li ti ) d l t th tMatch List‐I (Drill bits) with List‐II (Applications) and select the correctanswer using the codes given below the Lists:List‐I List‐IIList I List IIA. Core drill 1. To enlarge a hole to a certain depth so as to

accommodate the bolt head of a screwaccommodate the bolt head of a screwB. Reamer 2. To drill and enlarge an already existing hole in a

castinggC. Counter bore drill 3. To drill a hole before making internal

threadD. Tap drill 4. To improve the surface finish and dimensional

accuracy of the already drilled hole [C]Code:A B C D A B C D(a) 1 3 2 4 (b) 2 3 1 4(c) 2 4 1 3 (d) 3 2 4 1

Reaming, Boring, BroachingReaming, Boring, Broaching

By S K MondalBy S K MondalFor-2013 (IES, GATE & PSUs) Page 61

IFS‐2011IFS‐2011Wh t i th i diff b tWhat is the main difference between rose reamer

and chucking reamer ? Write in short about shelland chucking reamer ? Write in short about shell

reamer.

[5‐marks]

IES ‐ 1999Whi h f h f ll i l i hWhich one of the following processes results in thebest accuracy of the hole made?(a) Drilling (b) Reaming(c) Broaching (d) Boring(c) Broaching (d) Boring

B

IES ‐ 1999C id h f ll i diConsider the following statements regardingreaming process:1. Reaming generally produces a hole larger than its

own diameterown diameter2. Generally rake angles are not provided on reamers.3. Even numbers of teeth are preferred in reamer

design.des g .Which of these statements are correct?( ) d (b) d(a) 1 and 2 (b) 2 and 3(c) 1 and 3 (d) 1, 2 and 3 B(c) 1 and 3 (d) 1, 2 and 3 B

IES ‐ 1998 M h Li I i h Li II d l hMatch List‐I with List‐II and select the correct answerusing the codes given below the lists:

List‐I List‐IIA. Reaming 1. Smoothing and squaring surfaceA. Reaming 1. Smoothing and squaring surface

around the hole for proper seatingB Counter boring 2 Sizing and finishing the holeB. Counter‐boring 2.Sizing and finishing the holeC. Counter‐sinking 3. Enlarging the end of the holeD. Spot facing 4. Making a conical enlargement at the

end of the hole [D][ ]Code:A B C D A B C D(a) 3 2 4 (b) 2 3 4(a) 3 2 4 1 (b) 2 3 1 4(c) 3 2 1 4 (d) 2 3 4 1

IES ‐ 1994I iIn reaming process(a) Metal removal rate is high( ) g(b) High surface finish is obtained.( ) Hi h f i b i d(c) High form accuracy is obtained(d) High dimensional accuracy is obtained.( ) g y

D

( )GATE – 2007 (PI)R i i i il d f hi iReaming is primarily used for achieving(a) Higher MRR( ) g(b) Improved dimensional tolerance( ) Fi f fi i h(c) Fine surface finish(d) Improved positional tolerance( ) p p

B

IES ‐ 1993A h l f di i b d d b iA hole of 30 mm diameter is to be produced by reaming.The minimum diameter permissible is 30.00 mm whileh d bl hthe maximum diameter permissible is 30.05 mm. In thisregard, consider the following statements about thereamer size:1. The minimum diameter of the reamer can be less than 30 mm.2.The minimum diameter of the reamer cannot be less than 30 mm.3. The maximum diameter of the reamer can be more than 30.05 mm.3 3 54.The maximum diameter of the reamermust be less than 30.05 mm.

Of these statements [D]Of these statements [D](a) 1 and 4 are correct (b) 1 and 3 are correct(c) 2 and 3 are correct (d) 2 and 4 are correct

IES ‐ 1998A i h l hi h b i hiA component requires a hole which must be withinthe two limits of 25.03 and 25.04 mm diameter.Which of the following statements about thereamer size are correct?1. Reamer size cannot be below 25.03 mm.

b b2. Reamer size cannot be above 25.04 mm.3. Reamer size can be 25.04 mm.3. Rea e s e ca be 5.04 .4. Reamer size can be 25.03 mm.

l h h d b lSelect the correct answer using the codes given below:(a) 1 and 3 (b) 1 and 2(a) 1 and 3 (b) 1 and 2(c) 3 and 4 (d) 2 and 4 B

IAS ‐ 1999F i i f bli d h l h fFor reaming operation of blind hole, the type ofreamer required is(a) Straight flute reamer(b) Right hand spiral fluted reamer(b) Right hand spiral fluted reamer(c) Left hand spiral fluted reamer(d) None of the above

B


IAS ‐ 2003M t h Li t I (O ti ) ith Li t II (A li ti ) d l tMatch List I (Operation) with List II (Application) and selectthe correct answer using the codes given below the lists:

List I List IIList‐I List‐II(Operation) (Application)(A) R i U d f l i th d f h l t i it(A) Reaming 1. Used for enlarging the end of a hole to give it a

conical shape for a short distance(B) B i U d f l i l li i d i f h(B) Boring 2. Used for enlarging only a limited portion of the

hole [C](C) Counter boring 3. Used for finishing a hole(D) Counter sinking 4. Used for enlarging a hole

Codes:A B C D A B C D(a) 3 2 4 1 (b) 1 4 2 3(c) 3 4 2 1 (d) 1 2 4 3

IES ‐ 1992Sh ll dShell reamers are mounted on(a) Tool holders (b) Amour plates( ) ( ) p(c) Arbor (d) Shanks

[C][ ]

IES 2009IES 2009

IES ‐ 1993Th i f b i i dThemain purpose of boring operation, as comparedto drilling is to:(a) Drill a hole(b) Finish the drilled hole(b) Finish the drilled hole(c) Correct the hole(d) Enlarge the existing hole

D

IES – 1994, ISRO‐2008E l i i i i l h l i h iEnlarging an existing circular hole with a rotatingsingle point tool is called(a) Boring (b) Drilling(c) Reaming (d) Internal turning(c) Reaming (d) Internal turning.

A

IES – 1992, ISRO‐2010Whi h f h hi l b d f b iWhich of themachine tools can be used for boring1. Lathe2. Drilling machine

V i l illi hi3. Vertical milling machine4. Horizontal milling machine4 g(a) 1, 2, 3 (b) 1, 3, 4( ) d (d)(c) 2 and 4 (d) 1, 2, 3, 4

A

IES ‐ 2000Whi h f h f ll i f l l dWhich one of the following sets of tools or tools andprocesses are normally employed for making largediameter holes?(a) Boring tool(a) Boring tool(b) BTA tools (Boring and trepanning association) and

d llgun drill(c) Gun drill and boring tool(c) Gu d a d bo g too(d) Boring tools and trepanning

DD

IES ‐ 1996Whi h f h f ll i ?Which of the following statements are correct?1. A boring machine is suitable for a job shop.g j p2. A jig boring machine is designed specially for doing

more accurate work when compared to a verticalmore accurate work when compared to a verticalmilling machine.

3. A vertical precision boring machine is suitable forboring holes in cylinder blocks and liners.bo g o es cy de b oc s a d e s.

(a) 1, 2 and 3 (b) 1 and 2( ) d (d) d(c) 2 and 3 (d) 1 and 3.

A

IES ‐ 1995Th ff f i b i l bThe effects of setting a boring tool above centreheight leads to a/an.(a) Increase in the effective rake angle and a decrease inthe effective clearance anglethe effective clearance angle.(b) Increase in both effective rake angle and effectivel lclearance angle.(c) Decrease in the effective rake angle and an increase(c) ec ease t e e ect ve a e a g e a d a c easein the effective clearance angle.(d) D i b th ff ti k l d ff ti(d) Decrease in both effective rank angle and effectiveclearance angle.

CFor-2013 (IES, GATE & PSUs) Page 63

JWM 2010Consider the following operations regarding boring machines :1. Counterboring C i ki2. Countersinking

3. Trepanning3 p gWhich of the above operations is/are correct ?( ) d (b) d l(a) 1, 2 and 3 (b) 1 and 2 only(c) 2 and 3 only (d) 1 only(c) a d 3 o y (d) o yA

IES ‐ 2007A h f ll i hi i hi hAmong the following machining processes, whichcan be used formachining flat surfaces?1. Shaping 2. Milling 3. BroachingSelect the correct answer using the code given below:Select the correct answer using the code given below:(a) 1 and 2 only (b) 1 and 3 only(c) 2 and 3 only (d) 1, 2 and 3

DD

IES ‐ 1993A i (A) S l bl il l d i hAssertion (A): Soluble oils are employed withbroaching machine.Reason (R): Soluble oils have excellent coolingeffecteffect.(a) Both A and R are individually true and R is the

l fcorrect explanation of A(b) Both A and R are individually true but R is not the(b) ot a d R a e d v dua y t ue but R s ot t ecorrect explanation of A( ) A i t b t R i f l(c) A is true but R is false(d) A is false but R is true

A

IES – 1993, 2001A i (A) N f d i i i dAssertion (A): No separate feed motion is requiredduring broaching.Reason (R): The broaching machines are generallyhydraulically operatedhydraulically operated.(a) Both A and R are individually true and R is the

l fcorrect explanation of A(b) Both A and R are individually true but R is not the(b) ot a d R a e d v dua y t ue but R s ot t ecorrect explanation of A( ) A i t b t R i f l(c) A is true but R is false(d) A is false but R is true

B

IES ‐ 2001Th d i b hi hiThe screw and nut in a broaching machine arechanged from square thread to ACME thread. Thepower requirement of the machine at the samer.p.m. willp(a) Remain same(b)(b) Decrease(c) Increase(c) c ease(d) Depend on the operator

C

IAS ‐ 2004Whi h f h f ll i i f h l fWhich one of the following is true for the last fewteeth of a broach which are meant for finefinishing?(a) They have equal diameter(a) They have equal diameter(b) They have increasing diameter(c) They have decreasing diameter(d) They have alternately increasing and decreasing(d) They have alternately increasing and decreasingdiameter.

A

IES ‐ 2005 M t h Li t I (T l) ith Li t II (El t f T l) dMatch List I (Tool) with List II (Element of Tool) andselect the correct answer using the code given below theLists:Lists:

List I List IIA B h TA Broach 1. TangB. Reamer 2. PilotC. Drill 3. Front taperD. Carbide insert face mill 4. Bond [C]D. Carbide insert face mill 4. Bond [C]

5. Sweeper toothCodes:A B C D A B C DCodes:A B C D A B C D(a) 2 5 1 3 (b) 1 3 4 5( ) (d)(c) 2 3 1 5 (d) 1 5 4 3

IES ‐ 2002M h Li I i h Li II d l hMatch List I with List II and select the correct answer:List I (Machine tool) List II (Features)A. Lathe 1. Push or pull toolB Drilling machine 2 Rachet and pawlB. Drilling machine 2. Rachet and pawl

mechanismC Sh Di idi h dC. Shaper 3. Dividing headD. Broaching machine 4. Hollow tapered spindleg p p

5. Face plate [D]Codes:A B C D A B C DCodes:A B C D A B C D(a) 2 4 5 1 (b) 5 3 2 4(c) 2 3 5 4 (d) 5 4 2 1

MillingMilling



IES ‐ 2007Wh i h f i l b illiWhat is the process of removing metal by a millingcutter which is rotated against the direction oftravel of thework piece, called?(a) Down milling (b) Up milling(a) Down milling (b) Up milling(c) End milling (d) Face milling

BB

IES ‐ 1997C id th f ll i t t tConsider the following statements:In Up milling process,1. The cutter starts the cut from the machined surface andproceeds upwards.2. The cutter starts the cut from the top surface andproceeds downwards.3. The job is fed in a direction opposite to that of cutterrotation.4. The job is fed in the same direction as that of cutterrotation.Of these statements correct are:(a) 1 and 3 (b) 1 and 4(a) 1 and 3 (b) 1 and 4(c) 2 and 3 (d) 2 and 4 A

IES 2010Assertion (A): Climb or down milling operation ensuresAssertion (A): Climb or down milling operation ensuressmoother operation of the machine tool and longer tool lifeas compared to the conventional upmilling operationas compared to the conventional upmilling operation.Reason (R): In climb or down milling operation, therotational motion of the cutter as well as the feed motion ofrotational motion of the cutter as well as the feed motion ofthe work‐piece are in the same direction, and the depth ofcut is maximum at the entry point as the cutter engages thecut is maximum at the entry point as the cutter engages theworkpiece.(a) Both A and R are individually true and R is the correct(a) Both A and R are individually true and R is the correctexplanation of A(b) B th A d R i di id ll t b t R i NOT th t(b) Both A and R are individually true but R is NOT the correctexplanation of A( ) b f l(c) A is true but R is false(d) A is false but R is true B

IAS‐2009 mainIAS‐2009 mainDefine the term ‘ feed in milling’. [2‐Marks]

IES – 1995, ISRO‐2010I illi i id illiIn a milling operation two side milling cutters aremounted with a desired distance between them sothat both sides of a work piece can be milledsimultaneously. This set up is called.y p(a) Gang milling (b) Straddle milling( ) S ll (d) S d ll(c) String milling (d) Side milling.

B

IAS‐2009 MainIAS‐2009 MainWith k t h l i th i i l f kiWith a sketch, explain the principle of working

and variations of bed‐type milling machineand variations of bed type milling machine.

[9‐marks][9 marks]

IES ‐ 2006G illi iGang milling is a(a) Milling process for generating hexagonal surfaces( ) g p g g g(b) Process of cutting gears( ) P i hi h d(c) Process in which two or more cutters are usedsimultaneously(d) Milling operation combined with turning

C

IES ‐ 2009F hi i hi h f h f ll iFor machining, which one of the following gangmilling operations is employed?(a) Threads(b) Bores(b) Bores(c) Grooves(d) Steps on prismatic parts

D

IES – 2004, ISRO‐2011O b d f illi hi h h f ll iOne brand of milling machine has the following twoindex plates supplied along with the indexing head:Plate 1: 15, 16, 17, 18, 19, 20 hole circlesPlate 2: 21, 23, 27, 29, 31, 33 hole circlesPlate 2: 21, 23, 27, 29, 31, 33 hole circlesIt is proposed to mill a spur gear of 28 teeth using simpleindexing method Which one of the following combinationsindexing method. Which one of the following combinationsof index plate and number of revolutions is correct?( )(a) Plate 1: 1 revolution and 9 holes in 18 hole circles(b) Plate 2: 1 revolution and 9 holes in 21 hole circles( ) 9(c) Plate 2: 1 revolution and 9 holes In 33 hole circles(d) Plate re olution and 9 holes In hole circles B(d) Plate 1: 1 revolution and 9 holes In 15 hole circles B


IES ‐ 2000O f h i d l f illi hiOne of the index plates of a milling machinedividing head has the following hole circles: 15; 16;17; 18; 19; 20A gear wheel of 34 teeth has to be milled by simpleA gear wheel of 34 teeth has to be milled by simpleindexing method. To machine each tooth, the indexcrank has to be rotated throughcrank has to be rotated through(a) 17 holes in the 20‐hole circle(b) 18 holes in the 20‐hole circle( ) l ti d h l i h l i l(c) 1 revolution and 3 holes in 17‐hole circle(d) 1 revolution and 2 holes in 18‐hole circle C

IAS ‐ 1994A d d di idi h d i i d i h hA standard dividing head is equipped with thefollowing index plates1. Plate with 12, 16, 17, 18, 19, 20 holes circles2 Plate with 21 23 27 29 31 33 holes circles2. Plate with 21, 23, 27, 29, 31, 33 holes circles3. Plate with 37, 39, 41,43,47,49 holes circlesFor obtaining 24 divisions on a work piece by simpleindexingindexing(a) Hole plate 2 alone can be used(b) Hole plates 1 and 2 can be used(c) Hole plates 1 and 3 can be used(c) Hole plates 1 and 3 can be used(d) Any of the three hole plates can be used D

E lExampleA C l fl f f di i A C50 steel flat surface of dimensions 100 mm × 250 mm is to be produced on a horizontal axis milling machine. An HSS slab mill with a 100 mm diameter and 150 mm width is to be used for the purpose. The 5 p pmilling cutter has 8 teeth. Calculate the machining time assuming that entire Calculate the machining time assuming that entire stock can be removed in one depth of 2 mm.Given,Feed f = 0 13 mm/tooth Feed, f = 0.13 mm/tooth, Cutting speed, V = 20 m/min.

GATE ‐ 1995Li I Li IIList‐I List‐ II

(Manufacturing Processes) (Condition)( g ) ( )(A) Finish turning 1. Backlash eliminator(B) F i Z k(B) Forming 2. Zero rake(C) Thread cutting 3. Nose radius( ) g 3(D) Down milling 4. Low speed [A]dCodes:A B C D A B C D(a) 2 3 4 1 (b) 3 4 1 2(a) 2 3 4 1 (b) 3 4 1 2(c) 1 2 3 4 (d) 4 1 2 3

GATE ‐ 1993A illi h i 8 h i iA milling cutter having 8 teeth is rotating at 150rpm. If the feed per tooth is 0.1 mm, the table speedinmmperminute is(a) 120 (b) 187(a) 120 (b) 187(c) 125 (d) 70

AA

IES ‐ 2003I illi hi h i l i h ld iIn milling machine, the cutting tool is held inposition by(a) Chuck (b) Spindle(c) Arbor (d) Tool holder(c) Arbor (d) Tool holder

C

IES ‐ 2009Th b f illi hi i d h ldThe arbor of a milling machine is used to holdwhich one of the following?(a) Spindle (b) Over‐arm(c) Cutting tool (d) Mandrel(c) Cutting tool (d) Mandrel

C

IES ‐ 1994C id h f ll i iConsider the following operations:1. Cutting key ways on shaftsg y y2. Cutting external screw threads.

C i h f3. Cutting teeth of spur gears4. Cutting external splines.4 g pThose which can be performed with milling cutters

ld i l dwould include(a) 1 and 2 (b) 2,3 and 4(c) 1 and 3 (d) 1,2,3 and 4 D

IES ‐ 1992A f i h f li d illi f hA set of eight form relieved milling cutters for eachmodule is provided to enable cutting of gears ofdifferent(a) Materials(a) Materials(b) Types e.g. spur, helical, etc.(c) Number of teeth(d) Width of gears(d) Width of gears

C


GATE ‐ 1992I h i l illi ( /d )In horizontal milling process…………. (up/down)milling provides better surface finish and…………..(up‐down) milling provides longer tool life.

Ans down downAns. down, down

IES ‐ 1995A i (A) U illi li b illi iAssertion (A): Up milling or climb milling iscommonly used for machining castings andforgings.Reason (R): Up milling can be done on universalReason (R): Up milling can be done on universalmilling machines.( ) h d d d ll d h(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true D

IES ‐ 2005Whi h f h f ll i i ?Which one of the following statements is correct?In up‐milling operation, the undeformed chip thickness,p g p , p ,

a) Is zero at the start of the cut and increases to amaximum value just before the tooth disengages themaximum value just before the tooth disengages theworkpiece.

b) Increases to the maximum value at the centre of thetravel and decreases towards the end of tootht ave a d dec eases to a ds t e e d o tootengagement.

) H i l j t ft th t i t t d dc) Has a maximum value just after the cut is started anddrops to zero at the end of the cut.

d) Remains unchanged. A

IES ‐ 1993Cli b illi i h hil hi i bClimbmilling is chosenwhile machining because(a) The chip thickness increases gradually( ) p g y(b) It enables the cutter to dig in and depth of cut( ) Th ifi i i d d(c) The specific power consumption is reduced(d) Better surface finish can be obtained( )

D

IES ‐ 2002A ti (A) Vi t ll ll d illi hiAssertion (A): Virtually all modern milling machinesare capable of doing down‐milling.R (R) I d illi h d hReason (R): In down‐milling the cutter tends to pushthe work along and lift it upward from the table. Thisaction tends to eliminate any effect in looseness in theaction tends to eliminate any effect in looseness in thefeed screw and nut of the milling machine table andresults in smooth cutresults in smooth cut.(a) Both A and R are individually true and R is the correctexplanation of Aexplanation of A(b) Both A and R are individually true but R is not the

t l ti f Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true C

IES ‐ 2004Th i d f illi hil iThe cutting speed of a milling cutter while cuttingbrass is:(a) 45 to 60 m/min (b) 30 to 40 m/min(c) 25 to 35 m/min (d) 15 to 20 m/min(c) 25 to 35 m/min (d) 15 to 20 m/min

A

IES ‐ 1999A i h h l b illi fA straight teeth slab milling cutter of 100 mmdiameter and 10 teeth rotating at 200 r.p.m. is usedto remove a layer of 3 mm thickness from a steel bar.If the table feed is 400 mm/minute, the feed per4 / , ptooth in this operationwill be(a) 0 2 mm (b) 0 4 mm(a) 0.2 mm (b) 0.4 mm(c) 0.5 mm (d) 0.6 mm

AA

IES ‐ 2002A id d f di h hA side and face cutter 125 mm diameter has 10 teeth.It operates at a cutting speed of 14 m/min with atable traverse 100 mm/min. The feed per tooth ofthe cutter is(a) 10 mm (b) 2.86 mm( ) (d)(c) 0.286 mm (d) 0.8 mm

C

GATE – 2012 (PI) Common Data S1Data for a plain milling operation are given below.

Length of workpiece 200 mmLength of workpiece 200 mmCutter diameter 100 mmNo. of teeth 4Cutter speed 100 rpmCutter speed 100 rpmFeed 200 mm/minDepth of cut 2 mmTotal clearance (entry and exit) 5 mm [C]Total clearance (entry and exit) 5 mm [C]

Mean undeformed chip thickness (in microns) is(a) 142 (b) 100 (c) 71 (d) 50


GATE – 2012 (PI) Common Data S2Data for a plain milling operation are given below.

Length of workpiece 200 mmLength of workpiece 200 mmCutter diameter 100 mmNo. of teeth 4Cutter speed 100 rpmCutter speed 100 rpmFeed 200 mm/minDepth of cut 2 mmTotal clearance (entry and exit) 5 mmTotal clearance (entry and exit) 5 mm

Machining time for a single pass (in seconds) is(a) 60 (b) 66 (c) 126 (d) 150 [B]

IES ‐ 2004M t h Li t I (Milli bl ) ith Li t II (P b blMatch List I (Milling problem) with List II (Probablecauses) and select the correct answer using the codesgiven below the Lists:given below the Lists:

List I List IIA Ch T hi h f dA. Chatter 1. Too high feedB. Poor surface finish 2. Lack of rigidity in machine

fixtures, bar or workpieceC. Loss of accuracy 3. High cutting loady 3 g gD. Cutter burrs 4. Radial relief too great

5 Not enough lubricant [B]5. Not enough lubricant [B]Codes:A B C D A B C D(a) 2 3 (b) 2 3(a) 2 1 5 3 (b) 2 1 3 5(c) 4 5 2 3 (d) 4 2 3 5

IAS ‐ 2001Which one of the following statements are correct in respect ofWhich one of the following statements are correct in respect ofup‐milling and down‐milling?1. In up‐milling the cutter rotates in a direction opposite to that of

k l h d ll hp g pp

workpiece travel whereas in down‐milling the cutter rotates in adirection similar to that of workpiece travel.2 In down‐milling chip will be thin at the beginning and increase to a2. In down milling chip will be thin at the beginning and increase to amaximum at the end of the cut and reverse will be the case for a chipformed by up‐milling.

D illi i d i bl ith illi tt h i hi h di l3. Down‐milling is desirable with milling cutters having a high radialrake angle when compared to up‐milling.4. Down‐milling forces the work‐piece against the milling table to4. Dow g o ces t e wo p ece aga st t e g tab e toexert more pressure while up‐milling tends to lift the workpiece from thetable.Select the correct answer using the codes given below:Select the correct answer using the codes given below:Codes:(a) 1, 2 and 3 (b) 1, 2 and 4(a) 1, 2 and 3 (b) 1, 2 and 4(c) 3 and 4 (d) 1, 3 and 4 [D]

IAS ‐ 1998Whi h f th f ll i t t t t f fWhich of the following statements are true of facemilling?1. Face milling cutter is held on an arbor.2. It has two rake angles∙ axial rake and radial rake.g3. The maximum chip thickness equals the feed per

toothtooth.4. The chip thickness varies from a minimum at the

t t f t t i t th d f tstart of cut to a maximum at the end of cut.Select the correct answer using the codes given below:Codes :(a) 1 and 2 (b) 2 and 3(a) 1 and 2 (b) 2 and 3(c) 2 and 4 (d) 3 and 4 [B]

IAS ‐ 2001Whi h f h f ll i h i i bl fWhich of the following mechanisms are suitable forindexing the table of rotary transfer line?1. Rack and pinion 2. Ratchet and pawl3 Lead screw 4 Geneva mechanism3. Lead screw 4. Geneva mechanismSelect the correct answer by using the codes given below:Codes:( ) d (b) d(a) 1, 2 and 3 (b) 2, 3 and 4(c) 1, 3 and 4 (d) 1, 2 and 4 [D]

IAS ‐ 2000C id h f ll i h iConsider the following mechanisms:1. Geneva gearingg g2. Rack and pinion

R h d l3. Ratchet and pawlWhich of these mechanisms are used to index the worktable on a transfer machine?( ) d (b) d(a) 1 and 2 (b) 2 and 3(c) 1 and 3 (d) 1, 2 and 3 [D]

IAS ‐ 2003A illi f di i h h iA milling cutter of 70 mm diameter with 12 teeth isoperating at a cutting speed of 22 m/min and a feedof 0.05 mm/tooth. The feed perminute is(a) 110 m/min (b) 35 mm/min(a) 110 m/min (b) 35 mm/min(c) 6 mm/min (d) 60 mm/min

[D][D]

IES‐1994Whi h f h f ll i i i i d Which one of the following operations is carried out at the minimum cutting velocity if the machines are equally rigid and the tool work materials are the same?(a) Turning(b) G d(b) Grinding(c) Boring (c) o g(d) Milling [D]

IES ‐ 2012St t t (I) Vib ti i illi i d d d tStatement (I): Vibrations in milling are induced due tointerrupted cutting operation.S (II) Vib i b d lStatement (II):Vibrations can be suppressed to a large extentby using equal spacing of teeth along the periphery of thecutterscutters.(a) Both Statement (I) and Statement (II) are individuallyt d St t t (II) i th t l ti ftrue and Statement (II) is the correct explanation ofStatement (I)(b) B h S (I) d S (II) i di id ll(b) Both Statement (I) and Statement (II) are individuallytrue but Statement (II) is not the correct explanation ofSt t t (I)Statement (I)(c) Statement (I) is true but Statement (II) is false(d) Statement (I) is false but Statement (II) is true [B]


IES 2011IES 2011Match List –I with List –II and select the correct answer using gthe code given below the lists :

Li I Li IIList –I List –II

A Lathe 1 FluteA. Lathe 1. Flute

B. Shaper 2. Universal indexingB. Shaper 2. Universal indexing

C. Drilling machine 3. Leadscrew

CodesD. Milling machine 4. Rocker arm [B]

A B C D A B C D(a) 2 4 1 3 (b) 3 4 1 2(a) 2 4 1 3 (b) 3 4 1 2(c) 2 1 4 3 (d) 3 1 4 2

IES‐ 2002M h Li I i h Li II d l hMatch List I with List II and select the correctanswer:List I (Machine tools) List II (Machine tool parts)A Lathe 1 Lead strewA. Lathe 1. Lead strewB. Milling machine 2. Rocker armC. Shaper 3. Universal indexingD D illi hi Fl t [B]D. Drilling machine 4. Flute [B]

Codes:A B C D A B C D(a) 4 2 3 1 (b) 1 3 2 4( ) (d)(c) 4 3 2 1 (d) 1 2 3 4

Gear Manufacturingg

By S K Mondal

IES ‐ 1999C id h f ll i f hConsider the following processes for themanufacture of gears:1. Casting2 Powder metallurgy2. Powder metallurgy3. Machining from bar stock4. Closed die forgingTh t i i i d f b diThe correct sequence in increasing order of bendingstrength of gear teeth is(a) 1, 2, 3, 4 (b) 1, 2, 4, 3(c) 2 1 4 3 (d) 2 1 3 4 A(c) 2, 1, 4, 3 (d) 2, 1, 3, 4 A

IES ‐ 2006Whi h f h f ll i i / d f iWhich of the following is/are used for cuttinginternal gears?1. Gear hobber 2. Gear shaper3 Rack cutter 4 Jig borer3. Rack cutter 4. Jig borerSelect the correct answer using the codes given below:(a) Only 1 and 2 (b) Only 2 and 3( ) O l d (d) O l D(c) Only 1 and 4 (d) Only 2 D

IES ‐ 2005I h li l illi h i f h i f fIn helical milling, the ratio of the circumference ofthe gear blank to the lead of the helix determinesthe:(a) Proper speed to use(a) Proper speed to use(b) Proper feed and depth of cut required(c) Angle setting of the machine table(d) Gear ratio for table screw and dividing head(d) Gear ratio for table screw and dividing head

C

IES 2010Match List I with List II and select the correct answer usingMatch List I with List II and select the correct answer usingthe code given below the lists:

Li t I Li t IIList I List II(Type of work) (Manufacturing)

A. High rate production of worm Gears and 1. Gear shavingwormwheel [D]B. Generating internal gears and Cluster gears 2. GearmillingC Finishing of gear tooth profiles 3 Gear hobbingC. Finishing of gear tooth profiles 3. Gear hobbingD. Repair and piece production of gears 4. Gear shaping

A B C D A B C DA B C D A B C D(a) 2 1 4 3 (b) 3 1 4 2(c) 2 4 1 3 (d) 3 4 1 2

IES ‐ 1996G i illi hi i i lGear cutting on amilling machine using an involuteprofile cutter is a(a) Gear forming process(b) Gear generating process(b) Gear generating process.(c) Gear shaping process(d) Highly accurate gear producing process.

[A]

IES ‐ 2000 Whi h f h f ll i fWhich one of the following processes of gearmanufacture results in best accuracy of the involutegear tooth profile?(a) Milling(a) Milling(b) Hobbing(c) Rotary gear shaper(d) Rack type gear shaper(d) Rack type gear shaper

D


IES ‐ 2009A ti (A) G d d b l i fAssertion (A): Gears produced by employing form‐cutting principle using gear‐milling cutter on a millingmachine are not very accuratemachine are not very accurate.Reason (R): Production of the correct gear tooth profileemploying form cutting principle would require aemploying form‐cutting principle would require aseparate cutter for cutting different numbers of teetheven for the samemodule and also errors are associatedeven for the samemodule and also errors are associatedwith inaccurate operation of indexing mechanism.(a) Both A and R are true and R is the correct explanation of(a) Both A and R are true and R is the correct explanation ofA(b) B th A d R t b t R i NOT th t(b) Both A and R are true but R is NOT the correctexplanation of A( ) A i b R i f l(c) A is true but R is false(d) A is false but R is true [A]

IES ‐ 1996C id h f ll i fConsider the following processes of gearmanufacture:1. Milling with form cutter2 Rack type gear shaper (gear planer)2. Rack type gear shaper (gear planer)3. Rotary gear shaper (gear shaper)4. Gear hobbingTh t f th i i iThe correct sequence of these processes in increasingorder of accuracy of involute profile of the gear(a) 3, 2, 4, 1 (b) 2, 3, 4, 1(c) 3 2 1 4 (d) 2 3 1 4 [A](c) 3, 2, 1, 4 (d) 2, 3, 1, 4 [A]

IES ‐ 2009B hi h f h f ll i hi h h fBy which one of the following machines the teeth ofan internal spur gear can be cut accurately?(a) Milling machine(b) Slotting machine(b) Slotting machine(c) Hobbing machine(d) Gear‐shaping machine

[D]

IES ‐ 2004G h i i f f iGear shaping is a process of manufacturing gears.Which one of the following principles is employed by it?g p p p y y(a) Form cutting with cutter(b) G i h f i h i i(b) Generating tooth form with a reciprocating cutter(c) Generating tooth form by a rotating cutter( ) g y g(d) Generating form with a reciprocating and revolving

ttcutter

D

IES ‐ 1992I h bbiIn gear hobbing(a) Only hob rotates( ) y(b) Only gear blank rotates( ) B h h b d bl k(c) Both hob and gear blank rotate(d) Neither hob nor gear blank rotates( ) g

C

IES ‐ 2003A f h i hi d iA spur gear of 40 teeth is machined in a gearhobbing machine using a double start hob cutter.The speed ratio between the hob and the blank is(a) 1:20 (b) 1:40(a) 1:20 (b) 1:40(c) 40: 1 (d) 20: 1

DD

IES ‐ 2008Whi h hi i d fWhich machining processes are used for gearmanufacture?1. Form milling 2. Broaching3 Roll forming 4 Hobbing3. Roll forming 4. HobbingSelect the correct answer using the code given below:(a) 1, 2 and 3 (b) 1, 3 and 4( ) d (d) d(c) 1, 2 and 4 (d) 2, 3 and 4

C

IES ‐ 1999A 6 h h h bb d diff i lA 60‐teeth gear when hobbed on a differentialhobber with a two‐start hob, the index change gearratio is governed by which one of the followingkinematic balance equations?q(a) 1 revolution of gear blank = 1/60 of hob revolutions(b) l f bl k / f h b l(b) 1 revolution of gear blank = 2/60 of hob revolutions(c) 1 revolution of hob = 2/60 of blank revolutions(c) evo ut o o ob /60 o b a evo ut o s(d) 1 revolution of hob = 1/60 of blank revolutions

CC

IES ‐ 1997Whi h f h f ll i i d d fWhich of the following motions are not needed forspur gear cutting with a hob?1. Rotary motion of hob2 Linear axial reciprocator motion of hob2. Linear axial reciprocator motion of hob3. Rotary motion of gear blank4. Radial advancement of hob.S l t th t i th d i b lSelect the correct answer using the codes given below:(a) 1, 2 and 3 (b) 1, 3 and 4(c) 1, 2 and 4 (d) 2, 3 and 4DD


IES ‐ 2007Whi h f h f ll i h d iWhich of the following methods are gear generatingprocesses?1. Gear shaping2 Gear hobbing2. Gear hobbing3. Gear millingSelect the correct answer using the code given below:( ) d (b) d l(a) 1, 2 and 3 (b) 1 and 2 only(c) 2 and 3 only (d) 1 and 3 onlyy yB

( )GATE – 2007 (PI)Whi h f th f ll i f t iWhich one of the following gear manufacturingprocesses is NOT based on generation principle?p g p p(a) Gear Hobbing (b) Gear Shaping(c) Gear Milling (d) Gear Shaving

C

IES ‐ 1993 I l i i b f d bInternal gear cutting operation can be performed by(a) Milling( ) g(b) Shaping with rack cutter( ) Sh i i h i i(c) Shaping with pinion cutter(d) Hobbing( ) g

C

IAS ‐ 1998A i (A) I lAssertion (A): Internal gears are cut on a gearshaper.Reason (R): Hobbing is not suitable for cuttinginternal gearinternal gear.(a) Both A and R are individually true and R is the

l fcorrect explanation of A(b) Both A and R are individually true but R is not the(b) ot a d R a e d v dua y t ue but R s ot t ecorrect explanation of A( ) A i t b t R i f l(c) A is true but R is false(d) A is false but R is true [B]

IES ‐ 2006Whi h f h f ll i b b h bbiWhich of the following cannot be cut by hobbingprocess?(a) Helical gears (b) Bevel gears(c) Worm gears (d) Spur gears(c) Worm gears (d) Spur gears

B

IES ‐ 1996F h f f f ll d h bFor the manufacture of full depth spur gear byhobbing process, the number of teeth to be cut = 30,module = 3 mm and pressure angle = 20°. The radialdepth of cut to be employed should be equal top p y q(a) 3.75 mm (b) 4.50 mm( ) (d)(c) 6.00 mm (d) 6.75 mm

D

IES ‐ 1995Whil i h li l diff i lWhile cutting helical gears on a non‐differentialgear hobber, the feed change gear ratio is(a) Independent of index change gear ratio(b) dependent on speed change gear ratio(b) dependent on speed change gear ratio(c) Interrelated to index change gear ratio(d) Independent of speed and index change gear ratio.

C

IES ‐ 1992G b i hi fGear burnishing process for(a) Removing residual stresses from teeth roots( ) g(b) Surface finishing( ) U d(c) Under‐cut gears(d) Cycloidal gears( ) y g

B

IAS ‐ 2003Whi h f h f ll i i f fWhich one of the following is not a feature of gearhobbing process?(a) High rate of production(b) Generation of helical gears(b) Generation of helical gears(c) Very accurate tooth profile(d) Generation of internal gears

D


IAS ‐ 2001C id h f ll i i d i iConsider the following motions and setting in ahobbing machine:1. Hob rotation2 Job rotation2. Job rotation3. Axial reciprocating hob rotation4. Tilting of hob to its helix angleWhi h f th ti d tti i h bbiWhich of these motions and setting in a hobbingmachine are required to machine a spur gear?(a) 1, 2 and 3 (b) 2, 3 and 4(c) 1 2 and 4 (d) 1 3 and 4 C(c) 1, 2 and 4 (d) 1, 3 and 4 C

IES ‐ 1994C id h f ll i hi lConsider the following machine tools:1. Hobbing machineg2. Gear shaping machine

B hi hi3. Broaching machine.The teeth of internal spur gears can be cut inp g(a) 1, 2 and 3 (b) 1 and 2( ) d (d) d(c) 1and 3 (d) 2 and 3

D

IES ‐ 1992G l iGear lapping(a) An operation after heat treatment( ) p(b) An operation prior to heat treatment( ) A i d d i f di i i(c) An independent operation for gear reconditioning(d) None of the above( )

A

Screw Thread Screw Thread ManufacturingManufacturing

By S K Mondal

GATE ‐ 2003Q li h d d d bQuality screw threads are produced by(a) Thread milling( ) g(b) Thread chasing( ) Th d i i h i l i l(c) Thread cutting with single point tool(d) Thread casting( ) g

B

IES 2011l h d b d d bExternal threads can be produced by :

1. Rollingg2. Grinding3 Milling3. Milling

(a) 1 and 3 only(b) 1 and 2 only(c) 2 and 3only(c) 2 and 3only(d) 1, 2 and 3

D . Form grinding wheel produces very good qualityg g p y g q ythread.

IES 2010F d i b th i t l d t lFor producing both internal and externalscrew threads, themethod used is

(a) Thread chasing with multiple‐rib chasers(b) Thread milling and multiple‐thread cutters(c) Thread tapping with taps(c) Thread tapping with taps(d) Die threading with self‐opening die heads( ) g p g

B

IES ‐ 2007S h d d d lid d b iScrew threads are produced on solid rods by usingwhich of the following?(a) Dies (b) Punch(c) Mandrel (d) Boring bar(c) Mandrel (d) Boring bar

AA

ISRO‐2011ISRO‐2011Whi h f th f ll i th d i d t d f Which of the following screw thread is adapted for

power transmission in one directionpower transmission in one direction

(a) Acme threads (a) Acme threads

(b) Buttress threads( )

(c) Square threads ( ) q

(d) Multiple threads B


ISRO‐2010ISRO‐2010I t l d t l th d b d dInternal and external threads can be produced

on tapered surfaces conveniently byon tapered surfaces conveniently by

(a) Universal milling machine(a) Universal milling machine

(b) Plano miller(b) a o e

(c) Planetary milling machine( ) y g

(d) lathe C( )

IES ‐ 2012The differential screw is used in a

(a) Turnbuckle

(b) Micrometer

(c) Vernier Caliper

(d) C l(d) Coupler

BB

IES ‐ 2012Multistart threads are used to get

(a) Smaller linear displacement

(b) Larger linear displacement with assured self locking

(c) Larger linear displacement with no guarantee of self

lockinglocking

(d) None of the above(d) None of the above

CC

IES ‐ 2012Which of the following screw threads is adopted for

h dpower transmission in either direction

( ) ACME h d(a) ACME threads

(b) S th d(b) Square threads

(c) Buttress threads(c) Buttress threads

(d) Multiple threads(d) Multiple threads

BB

Sh Pl SlShaper, Planner, Slotter


GATE ‐ 2005A 6 fl f f l i bA 600 mm x 30 mm flat surface of a plate is to befinish machined on a shaper. The plate has beenfixed with the 600 mm side along the tool traveldirection. If the tool over‐travel at each end of theplate is 20 mm, average cutting speed is 8 m/min,feed rate is 0 3 mm/stroke and the ratio of returnfeed rate is 0.3 mm/stroke and the ratio of returntime to cutting time of the tool is 1:2, the time

i d f hi i ill brequired formachining will be(a) 8 minutes (b) 12 minutes(c) 16 minutes (d) 20 minutesBB

IES ‐ 2004C id h f ll i li hiConsider the following alignment tests on machinetools1. Straightness 2. Flatness3 Run out 4 Parallelism3. Run out 4. ParallelismWhich of the above alignment tests on machine tools arecommon to both lathe and shaper?(a) 1 and 2 (b) 2 and 3(a) 1 and 2 (b) 2 and 3(c) 3 and 4 (d) 1 and 4D

IES ‐ 2001In a shapermachine, themechanism for tool feed is

(a) Geneva mechanism

(b) Whitworth mechanism

( )(c) Ratchet and Pawl mechanism

(d) W d L d(d) Ward‐ Leonard system

CC

IES 2010Assertion (A): Longitudinal cutting motion of theAssertion (A): Longitudinal cutting motion of thetool and cross‐wise feed motion of the job generatesfl f i l iflat surfaces in planning process.Reason (R): Jobs used in planning machines are( ) J p ggenerally long and heavy compared to shaping.( ) B th A d R i di id ll t d R i th(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is NOT thecorrect explanation of Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true D


IES ‐ 1997Whi h f h f ll i h d fWhich of the following are the advantages of ahydraulic shaper over amechanically driven shaper?1. More strokes per minute can be obtained at a givencutting speedcutting speed.2. The cutting stroke has a definite stopping point.3. It is simpler in construction.4 Cutting speed is constant throughout most of the4. Cutting speed is constant throughout most of thecutting stroke.

l h h d b lSelect the correct answer using the codes given below:(a) 1 and 2 (b) 1 and 4(a) 1 and 2 (b) 1 and 4(c) 2 and 4 (d) 1, 3 and 4 B

IES ‐ 1995I h i l h h l h f k iIn a mechanical shaper, the length of stroke isincreased by(a) Increasing the centre distance of bull gear and crankpinpin(b) Decreasing the centre distance of bull gear and

kcrank pin(c) Increasing the length of the ram(c) c eas g t e e gt o t e a(d) Decreasing the length of the slot in the slotted lever

AA

IES – 1994, ISRO‐2008Gi h i d / i hGiven that, average cutting speed = 9 m/min, thereturn time to cutting time ratio is = 1 : 2, the feedrate = 0.3 mm/stroke, the clearance at each end ofcut = 25 mm and that the plate is fixed with 700 mm5 p 7side along the direction of tool travel, the timerequired for finishing one flat surface of a plate ofrequired for finishing one flat surface of a plate ofsize 700 x 30 mm in a shaper, will be( ) (b)(a) 10 min (b) 12.5 min(c) 15 min (d) 20 min(c) 15 min (d) 20 min

B

IAS ‐ 1995Size of a shaper is given by

(a) Stroke length (b) Motor power

(c) Weight of the machine (d) Table size

AA

ISRO‐2010ISRO‐2010Th tti d f th t l i h i lThe cutting speed of the tool in a mechanical

shaper isshaper is

(a) Maximum at the beginning of the cutting stroke(a) Maximum at the beginning of the cutting stroke

(b) Maximum at the end of the cutting stroke( ) g

(c) Maximum at the middle of the cutting stroke( ) g

(d) Minimum at the middle of the cutting stroke

C

IAS ‐ 1994S k f h i hi i I kStroke of a shaping machine is 250 mm. It makes 30double strokes perminute. Overall average speed ofoperation is(a) 3 75 m/min (b) 5 0 m/min(a) 3.75 m/min (b) 5.0 m/min(c) 7.5 m/min (d) 15 m/min

DD

GATE 2012 (PI)GATE‐2012 (PI)In a shaping process, the number of double strokes per

d h k f hminute is 30 and the quick return ratio is 0.6. If the

length of the stroke is 250 mm the average cuttinglength of the stroke is 250 mm, the average cutting

velocity in m/min isvelocity in m/min is

(a) 3.0 (b) 4.5 (c) 7.5 (d) 12.0( ) 3 ( ) 4 5 ( ) 7 5 ( )

D

Grinding & FinishingG d g & s g


GATE ‐2011 (PI)GATE ‐2011 (PI)Grinding ratio is defined asGrinding ratio is defined as

volume of wheel wear(a)( )volume of work material removedvolume of work material removed(b)(b)

volume of wheel wearcutting speedcutting speed(c)

feedl it di l f d

Blongitudinal feed(d)transverse feed


IES 2009IES 2009

[2 MARKS]

GATE ‐ 1995A h i l hi iAmong the conventional machining processes,maximum specific energy is consumed in(a) Turning (b) Drilling(c) Planning (d) Grinding(c) Planning (d) Grinding

D

GATE ‐ 1998Id l f h d b hIdeal surface roughness, as measured by themaximum height of unevenness, is best achievedwhen, thematerial is removed by(a) An end mill(a) An end mill(b) A grinding wheel(c) A tool with zero nose radius(d) A ball mill(d) A ball mill

B

GATE ‐ 1998I hi i i b i i l i iIn machining using abrasive material, increasingabrasive grain size(a) Increases the material removal rate(b) Decreases the material removal rate(b) Decreases the material removal rate(c) First decreases and then increases the materialremoval rate(d) First increases and then decreases the material(d) First increases and then decreases the materialremoval rate

DD

GATE ‐ 2000Ab i i l d i i di h l l dAbrasive material used in grinding wheel selectedfor grinding ferrous alloys is(a) Silicon carbide (b) Diamond(c) Aluminium oxide (d) Boron carbide(c) Aluminium oxide (d) Boron carbide

C

GATE ‐ 2002Th h d f i di h l i d i d bThe hardness of a grinding wheel is determined bythe(a) Hardness of abrasive grains(b) Ability of the bond to retain abrasives(b) Ability of the bond to retain abrasives(c) Hardness of the bond(d) Ability of the grinding wheel to penetrate the workpiecepiece

B

GATE ‐ 2006If h b i i i i d i lIf each abrasive grain is viewed as a cutting tool,then which of the following represents the cuttingparameters in common grinding operations?(a) Large negative rake angle low shear angle and high(a) Large negative rake angle, low shear angle and highcutting speed(b) k l l h l d h h(b) Large positive rake angle, low shear angle and highcutting speed(c) Large negative rake angle, high shear angle and lowcutting speedcutting speed(d) Zero rake angle, high shear angle and high cuttingspeed A

GATE ‐ 1997Li I Li IIList I List II

(A) Grinding 1. Surface for oil retention( ) g(B) Honing 2. Surface for max. load

capacitycapacity(C) Super‐finishing 3. Surface of limiting frictionD) Burnishing 4. Surface of matte finish

S f f li5. Surface for pressure sealing6. Surface for interference fit.

A (A) (B) (C) (D)Ans. (A) ‐3, (B) ‐1, (C)‐2, (D)‐5

IES ‐ 2005C id h f ll i i fConsider the following statements in respect ofgrinding?1. The pitch of the grit cutting edges is larger than the

pitch of the milling cutterpitch of the milling cutter.2. The cutting angles of the grits have a random

geometry.3. The size of the chip cuts is very small for grinding.3. e s e o t e c p cuts s ve y s a o g d g.Which of the statements given above are correct?( ) d (b) d(a) 1 and 2 (b) 2 and 3(c) 1 and 3 (d) 1, 2 and 3 B(c) 1 and 3 (d) 1, 2 and 3 B


IES ‐ 2009Whi h f h f ll i i NOT d b iWhich one of the following is NOT used as abrasivematerial in grinding wheels?(a) Aluminium oxide(b) Silicon carbide(b) Silicon carbide(c) Cubic boron nitride(d) Manganese oxide

D

IES ‐ 1997Whi h f h f ll i i l i d hWhich one of the following materials is used as thebonding material for grinding wheels?(a) Silicon carbide(b) Sodium silicate(b) Sodium silicate(c) Boron carbide(d) Aluminum oxide

B

IES ‐ 1996G i di h l i id b l d d h hGrinding wheel is said to be loaded when the(a) Metal particles get embedded in the wheel surface( ) p gblocking the interspaces between cutting grains.(b) Bonding material comes on the surface and the(b) Bonding material comes on the surface and thewheel becomes blunt.(c) Work piece being ground comes to a stop incylindrical grinding.cy d ca g d g.(d) Grinding wheel stops because of very large depth of

tcut

A

IES ‐ 2001S ifi i i i i diSpecific cutting energy is more in grinding processcompared to turning because(a) Grinding (cutting) speed is higher(b) The wheel has multiple cutting edges (grains)(b) The wheel has multiple cutting edges (grains)(c) Plaguing force is significant due to small chip size(d) Grinding wheel undergoes continuous wear

B

IES ‐ 1996S ifi i i i diSpecific energy requirements in a grinding processare more than those in turning for the same metalremoval rate because of the(a) Specific pressures between wheel and work being(a) Specific pressures between wheel and work beinghigh.(b) S ff f h l b h l(b) Size effect of the larger contact areas between wheeland work.(c) High cutting velocities(d) Hi h h t d d d i i di(d) High heat produced during grinding

D

IES ‐ 1994Th i f h f i f i lThe ratio of thrust force to cutting force is nearly 2.5in(a) Turning (b) Broaching(c) Grinding (d) Plain milling(c) Grinding (d) Plain milling

C

IES ‐ 1992A i (A) Vi ifi d b d i f d f hiAssertion (A): Vitrified bond is preferred for thingrinding wheels.Reason (R): Vitrified bond is hard brittle.(a) Both A and R are individually true and R is the(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Aco ect e p a at o o(c) A is true but R is false(d) f l b(d) A is false but R is trueAA

IES ‐ 2000A ti (A) Th ti f tti f t th t f iAssertion (A): The ratio of cutting force to thrust force isvery high in grinding process as compared to othermachining processesmachining processes.Reason (R): Random orientation and effective negativerake angles of abrasive grains increase the cutting forcerake angles of abrasive grains increase the cutting forceand adversely affect the cutting action and promoterubbing actionrubbing action.(a) Both A and R are individually true and R is the correctexplanation of Aexplanation of A(b) Both A and R are individually true but R is not the

t l ti f Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true D

IES ‐ 1995S f i l b i ll i d dSoft materials cannot be economically grind due to(a) The high temperatures involved( ) g p(b) Frequent wheel clogging( ) R id h l(c) Rapid wheel wear(d) Lowwork piece stiffness( ) p

B


IES 2010I l ti t th i h l fIn relation to the peripheral or surfacespeeds of the grinding wheel and that of thep g gworkpiece in cylindrical grinding of alloysteel workpieces the grinding wheel speed issteel workpieces, the grinding wheel speed is

(a) Less than the speed of the workpiece( ) p p(b) Same as the speed of the workpiece(c) Double the speed of the workpiece(d) 6 t ti th d f th k i(d) 65 to 75 times the speed of the workpiece.DD

IES ‐ 2009Gi h h i h l d f h i diGiven that the peripheral speed of the grindingwheel of 100 mm diameter for cylindrical grindingof a steel work piece is 30 m/s, what will be theestimated rotational speed of the grinding wheel inp g grevolution perminute (r.p.m.)?(a) 11460 (b) 30(a) 11460 (b) 5730(c) 2865 (d) 95

BB

IES ‐ 2002Whi h f h f ll i i l d iWhich of the following materials are used ingrinding wheel?1. Aluminium oxide2 Cubic boron nitride2. Cubic boron nitride3. Silicon carbideSelect the correct answer using the codes given below:( ) d (b) d(a) 1, 2 and 3 (b) 1 and 2(c) 2 and 3 (d) 1 and 3A

IES – 2001, ISRO‐2009Th ki i di h l i ' A 6 L V 'The marking on a grinding wheel is '51 A 36 L 5 V 93'.The code '36' represents the(a) Structure(b) Grade(b) Grade(c) Grain‐ size(d) Manufacturer's number

C

IES ‐ 2000Th f ki "S K S" i diThe sequence of markings "S 14 K 14 S" on a grindingwheel represents respectively(a) Bond type, structure, grade, grain size and abrasivetypetype(b) Abrasive type, grain size, grade, structure and bondtype(c) Bond type, grade, structure, grain size and abrasive(c) o d type, g ade, st uctu e, g a s e a d ab as vetype(d) Ab i t t t d i i d b d(d) Abrasive type, structure, grade, grain size and bondtype B

IES ‐ 1995I h i di h l f A 6 G B B d fIn the grinding wheel of A 60 G 7 B 23, B stands for(a) Resinoid bond (b) Rubber bond( ) ( )(c) Shellac bond (d) Silicate bond.

A

IES ‐ 1993T l lif i h f i di h l i h iTool life in the case of a grinding wheel is the time(a) Between two successive regrinds of the wheel( ) g(b) Taken for the wheel to be balanced( ) T k b i h l d i(c) Taken between two successive wheel dressings(d) Taken for a wear of 1mm on its diameter( )

C

IES ‐ 2001A i (A) H d h l h f i diAssertion (A): Hard wheels are chosen for grindinghard metals.Reason (R): In hard wheels only the abrasive grainsare retained for long timeare retained for long time.(a) Both A and R are individually true and R is the

l fcorrect explanation of A(b) Both A and R are individually true but R is not the(b) ot a d R a e d v dua y t ue but R s ot t ecorrect explanation of A( ) A i t b t R i f l(c) A is true but R is false(d) A is false but R is true D

IES ‐ 1994C id h f ll i diConsider the following statements regardinggrinding of high carbon steel:1. Grinding at high speed results in the reduction ofchip thickness and cutting forces per gritchip thickness and cutting forces per grit.2. Aluminium oxide wheels are employed.3. The grinding wheel has to be of open structure.Of these statementsOf these statements(a) 1, 2 and 3 are correct (b) 1 and 2 are correct(c) 1 and 3 are correct (d) 2 and 3 are correctBB


IES ‐ 1999C id h f ll iConsider the following reasons:1. Grinding wheel is softg2. RPM of grinding wheel is too low

C i fi3. Cut is very fine4. An improper cutting fluid is used4 p p gA grinding wheel may become loaded due to reasonst t d tstated at(a) 1 and 4 (b) 1 and 3(c) 2 and 4 (d) 2 and 3 C

IES ‐ 2001D d d i i d i fl id fDry and compressed air is used as cutting fluid formachining(a) Steel (b) Aluminium(c) Cast iron (d) Brass(c) Cast iron (d) Brass

C

IES ‐ 1993I l i di h k i ill bIn centreless grinding, thework piece centrewill be(a) Above the line joining the two wheel centres( ) j g(b) Below the line joining the two wheel centres( ) O h li j i i h h l(c) On the line joining the two wheel centres(d) At the intersection of the line joining the wheel( ) j gcentres with the work plate plane.

A

IES ‐ 2000C id h f ll i dConsider the following advantages:1. Rapid processp p2. Work with keyways can be ground

N k h ldi d i i i d3. No work holding device is required.Which of these are the advantages of centre lessggrinding?( ) d (b) d(a) 1, 2 and 3 (b) 1 and 2(c) 2 and 3 (d) 1 and 3 D

IES ‐ 1996A i di h l f di i iA grinding wheel of 150 mm diameter is rotating at3000 rpm. The grinding speed is

A

IES ‐ 1993C id h f ll iConsider the following parameters:1. Grinding wheel diameter.g2. Regulating wheel diameter.

S d f h i di h l3. Speed of the grinding wheel.4. Speed of the regulating wheel.4 p g g5. Angle between the axes of grinding and regulatingh lwheels.

Among these parameters, those which influence theg paxial feed rate in centreless grinding would include(a) 2 4 and 5 (b) 1 2 and 3(a) 2, 4 and 5 (b) 1, 2 and 3(c) 1, 4 and 5 (d) 3, 4 and 5 A

IES ‐ 2007H i P i f fi i h f h d ?Honing Process gives surface finish of what order?(a) 10 µm (CLA) (b) 1.0 µm (CLA)( ) µ ( ) ( ) µ ( )(c) 0.1 µm (CLA) (d) 0.01 µm (CLA)

C

IES ‐ 1992CLA l f H i iCLA value for Honing process is(a) 6 (b) 0.05 ‐ 3.0( ) ( ) 5 3(c) 0.05 ‐ 1.0 (d) 0.025 ‐ 0.1

C

IES ‐ 2012St t t (I) H i i b di t Statement (I): Honing is an abrading process to remove stock from metallic surfaces.Statement (II):Honing is commonly done on internal surfaces.(a) Both Statement (I) and Statement (II) areindividually true and Statement (II) is the correcty ( )explanation of Statement (I)(b) Both Statement (I) and Statement (II) are(b) Both Statement (I) and Statement (II) areindividually true but Statement (II) is not the correctexplanation of Statement (I)explanation of Statement (I)(c) Statement (I) is true but Statement (II) is false( ) ( ) ( ) [ ](d) Statement (I) is false but Statement (II) is true [B]


IES ‐ 2001M t h Li t I (C tti T l ) ith Li t II (A li ti )Match List‐I (Cutting Tools) with List‐II (Applications)and select the correct answer using the codes givenbelow the lists:below the lists:

List I List IIA T i l F f fi i hi bA. Trepanning tool 1. For surface finishing by

honingB. Side milling cutter 2. For machining gearsC. Hob cutter 3. For cutting keyways in shafts3 g y yD. Abrasive sticks 4. For drilling large diameter

holes [B][ ]Codes:A B C D A B C D(a) 1 3 2 4 (b) 4 3 2 1(a) 1 3 2 4 (b) 4 3 2 1(c) 1 2 3 4 (d) 4 2 3 1

IES ‐ 1992A f fi i h f i CLA lA surface finish of 0.025 – 0.1 micrometer CLA valuesis to by produced. Which machining process wouldyou recommend?(a) Grinding (b) Rough turning(a) Grinding (b) Rough turning(c) Lapping (d) Honing

CC

IES ‐ 1992B ffi h l d fBuffing wheels are mode of(a) Softer metals (b) Cotton fabric( ) ( )(c) Carbon (d) Graphite

B

IAS ‐ 2004Th i ff f h i i ifiThe size effect refers to the increase in specificcutting energy at low values of under formed chipthickness. It is due towhich one of the following?(a) Existence of ploughing force(a) Existence of ploughing force(b) Work hardening(c) High strain rate(d) Presence of high friction at chip‐tool interface(d) Presence of high friction at chip‐tool interface.

A

IAS ‐ 2000C id h f ll i i fConsider the following statements in respect of agrinding wheel of specification, 51‐A‐ 36‐L‐7‐R‐23,using the standard alphanumeric codification:1 Abrasive used in the wheel is aluminum oxide1. Abrasive used in the wheel is aluminum oxide2. The grain size of abrasive is medium3. The wheel grade is medium hard4 It has an open structure4. It has an open structure5. It has resinoid as bonding agentWhich (If these statements are correct?(a) 1 2 and 3 (b) 1 3 and 4(a) 1, 2 and 3 (b) 1, 3 and 4(c) 2, 3 and 5 (d) 1, 4 and 5 A

IAS ‐ 1999A i (A) Th d f i di h l iAssertion (A): The grade of a grinding wheel is ameasure of hardness of the abrasive used for thewheel.Reason (R): Grading is necessary for making rightReason (R): Grading is necessary for making rightselection of thewheel for a particular work.( ) h d d d ll d h(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true D

IAS ‐ 2001Consider the following statements:Consider the following statements:The set‐up for internal centreless grinding consists of aregulating wheel, a pressure roll and a support roll, betweenregulating wheel, a pressure roll and a support roll, betweenwhich the tubular workpiece is supported with the grindingwheel within the tube, whereinTh i di h l k i d l i h l1.The grinding wheel, workpiece and regulating wheel centers

must lie on one line2 The directions of rotation of workpiece and grinding wheel are2.The directions of rotation of workpiece and grinding wheel aresame3.The directions of rotation of pressure roll, support roll and3 p , ppregulating wheel are same4.The directions of rotation of grinding wheel and regulatingh lwheel are same

Which of these statements are correct?( ) d (b) d(a) 1, 2 and 3 (b) 1, 3 and 4(c) 2 and 3 (d) 3 and 4 A

IAS ‐ 1997Whi h f h f ll i i l h d?Which of the following pairs are correctly matched?1. Drill press : Trepanningp p g2. Centreless grinding: Through feeding

C l h R3. Capstan lathe: Ram type turretSelect the correct answer using the codes given below:g gCodes:( ) d (b) d(a) 1 and 2 (b) 1, 2 and 3(c) 1 and 3 (d) 2 and 3 B(c) 1 and 3 (d) 2 and 3 B

IAS ‐ 2007 M t h Li t I ith Li t II d l t th tMatch List I with List II and select the correct answerusing the code given below the Lists:Li I Li IIList I List II(Machine Tool/ Cutting Tool) (Part/ Characteristics)A. Screw cutting lathe1. Self locking taperB. Drill 2. Chasing dialgC. End mill 3. Wiper insertD Grinding wheel 4 Self releasing taperD. Grinding wheel 4. Self releasing taper

5. Balance weights [B]C d A B C D A B C DCode:A B C D A B C D(a) 4 5 3 1 (b) 2 1 4 5(c) 4 1 3 5 (d) 2 5 4 1


IAS ‐ 1999Whi h f h f ll i iWhich one of the following processing sequenceswill give the best accuracy as well as surface finish?(a) Drilling, reaming and grinding(b) Drilling boring and grinding(b) Drilling, boring and grinding(c) Drilling, reaming and lapping(d) Drilling, reaming and electroplating

C

IAS ‐ 2001Whi h f h f ll i i di h l ( i hWhich one of the following grinding wheels (withGrade, Grit and Bond) is suitable for cuttergrinding?(a) K 60 vitrified (b) K 320 vitrified(a) K 60 vitrified (b) K 320 vitrified(c) T 60 resinoid (d) T 320 resinoid

A

NC, CNC & RoboticsNC, CNC & Robotics


IAS ‐ 1996A i (A) Th l fAssertion (A): The temperature control of anelectric iron is an example of servomechanism.Reason (R): It is an automatic control system.(a) Both A and R are individually true and R is the(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Aco ect e p a at o o(c) A is true but R is false(d) f l b(d) A is false but R is trueDD

GATE ‐ 1994CNC hi h i lCNC machines are more accurate than conventionalmachines because they have a high resolutionencoder and digital read‐outs for positioning.

True or false?

Ans. True

IES ‐ 1999C id h f ll i diConsider the following statements regardingnumerically controlled machine tools:1. They reduce non‐productive time2 They reduce fixturing2. They reduce fixturing3. They reduce maintenance costWhich of these statements are correct?( ) d (b) d(a) 1, 2 and 3 (b) 1 and 2(c) 2 and 3 (d) 1 and 3B

IES ‐ 1995C id h f ll i h i i fConsider the following characteristics ofproduction jobs:1. Processing of parts frequently in small lots2 Need to accommodate design changes of products2. Need to accommodate design changes of products.3. Low rate of metal removal4. Need for holding close tolerancesTh h t i ti hi h f th h i fThe characteristics which favour the choice ofnumerically controlled machines would include(a) 1, 2 and 3 (b) 2, 3 and 4(c) 1 3 and 4 (d) 1 2 and 4 D(c) 1, 3 and 4 (d) 1, 2 and 4 D

IES ‐ 2009I hi h f h f ll i hi i lIn which of the following machining manual partprogramming is done?(a) CNC machining (b) NC machining(c) DNC machining (d) FMS machining(c) DNC machining (d) FMS machining

B

GATE ‐ 1993Wi h f NC hi hi h f hWith reference to NC machine, which of thefollowing statement is wrong?(a) Both closed‐loop and open‐loop control systems areusedused(b) Paper tapes, floppy tapes and cassettes are used forddata storage(c) Digitizers may be used as interactive input devices(c) g t e s ay be used as te act ve put dev ces(d) Post processor is an item of hardware

DD


IES ‐ 2007Wh h i f NC hi ?What are themain components of an NCmachine?1. Part programp g2. Machine Control Unit

S3. Servo motorSelect the correct answer using the code given below:g g(a) 1, 2 and 3 (b) 1 and 2 only( ) d l (d) d l(c) 2 and 3 only (d) 1 and 3 onlyAA

JWM 2010Consider the following components regarding numericalConsider the following components regarding numericalcontrol system :1. Programme of instructions2 Machine control unit2. Machine control unit3. Processing equipment

Which of these are correct ?(a) 1 2 and 3 (b) 1 and 2 only(a) 1, 2 and 3 (b) 1 and 2 only(c) 2 and 3 only (d) 1 and 3 onlyA

IES ‐ 2009Wh i h f lli iWhat is the purpose of satellite computers inDistributed Numerical Control machines?(a) To act as stand‐by systems(b) To share the processing of large size NC programs(b) To share the processing of large‐size NC programs(c) To serve a group of NC machines(d) To network with another DNC setup

C

IES ‐ 1999C id h f ll iConsider the following components:1. A dedicated computerp2. Bulk memory

T l i i li3. Telecommunication linesWhich of these components are required for a DNCp qsystem?( ) d (b) d(a) 2 and 3 (b) 1 and 2(c) 1, 2 and 3 (d) 1 and 3

CC

JWM 2010Consider the following advantages of DNC systems :Consider the following advantages of DNC systems :1. Time‐sharing2. Greater computational capability3 Remote computer location3. Remote computer location

Which of the above is/are correct ?( ) d l (b) d l(a) 1 and 2 only (b) 2 and 3 only(c) 2 only (d) 1, 2 and 3y 3

DD

IES – 2002 S‐1 M t h Li t I ith Li t II d l t th tMatch List I with List II and select the correctanswer:

List I List II(NCmachine tool systems) (Features)( y ) ( )A. NC system 1. It has an integrated automatic tool

changing unit and a componentchanging unit and a componentindexing device

B CNC t A b f hi t lB. CNC system 2. A number of machine tools arecontrolled by a computer. No tape

d th t ireader, the part program istransmitted directly to the

hi t l f thmachine tool from thecomputer memory

dIES – 2002 Contd….. From S‐1 C DNC t Th t ll i t fC. DNC system 3. The controller consists of

soft‐wired computer andh d i d l i G hihard‐ wired logic Graphicdisplay of tool path isl iblalso possible

D. Machining centre 4. The instructions on tape isprepared in binarydecimal form and operated byp ya series of codedinstructions [C][ ]

Codes:A B C D A B C D(a) 4 2 3 1 (b) 1 3 2 4(a) 4 2 3 1 (b) 1 3 2 4(c) 4 3 2 1 (d) 1 2 3 4

IAS‐2011 mainIAS‐2011 mainE l i t l t t h t i ti h f NCExplain, at least two, characteristics each of NC,

CNC and DNCCNC and DNC.

[10‐Marks][10 Marks]

IAS‐2009 mainIAS‐2009 mainWh t i th f ti f t t ?What is the function of stepper motor?

[2 marks][2 – marks]


IAS‐2010 MainIllustrate with the help of neat sketches the differences

between open‐loop and closed‐loop control in NC

system. Why is feedback not possible in open‐loop

control s stem ?control system ?

[22 Marks][22‐Marks]

GATE ‐ 2007Whi h f i NOT d i i i dl Which type of motor is NOT used in axis or spindle drives of CNC machine tools?(a) Induction motor (b) DC servo motor(c) Stepper motor (d) Linear servo motor(c) Stepper motor (d) Linear servo motor

A

IES ‐ 1994F d d i i CNC illi hi id dFeed drives in CNC milling machines are providedby(a) Synchronous motors(b) Induction motors(b) Induction motors(c) Stepper motors(d) Servo‐motors.

IES ‐ 2002I CNC hi l d i d dIn a CNCmachine tool, encoder is used to sense andcontrol(a) Table position(b) Table velocity(b) Table velocity(c) Spindle speed(d) Coolant flow

B

GATE ‐ 1997I i i l NC hi h lidIn a point to point control NC machine, the slidesare positioned by an integrally mounted steppermotor drive. If the specification of the motor is1o/pulse, and the pitch of the lead screw is 3.6 mm,/p , p 3 ,what is the expected positioning accuracy?

( ) ( )bμ μμ μ

( ) 1 ( ) 10( ) 50 ( ) 100a m b mc m d m

B

μ μ( ) ( )

B

( )GATE – 2007 (PI)I CNC hi f d d i t tIn a CNC machine feed drive, a stepper motorwith step angle of 1.8o drives a lead screw withp gpitch of 2 mm. The Basic Length Unit (BLU) forthis drive isthis drive is(a) 10 microns (b) 20 microns( ) ( )(c) 40 microns (d) 100 micronsA

GATE – 2008 (PI)A stepper motor has 150 steps. The output shaft of the

d l l d l d f hmotor is directly coupled to a lead screw of pitch 4 mm,

which drives a table If the frequency of pulse supply towhich drives a table. If the frequency of pulse supply to

the motor is 200 Hz, the speed of the table (in mm/min)the motor is 200 Hz, the speed of the table (in mm/min)

is

(a) 400 (b) 320 (c) 300 (d) 280

B

Examplel d d l l dA DC servomotor is coupled directly to a leadscrew

which drives the table of an NC machine tool. Adigital encoder, which emits 500 pulses perrevolution, is mounted on the other end of theleadscrew. If the leadscrew pitch is 5 mm and themotor rotates at 600 rpm, calculate(a) The linear velocity of the table(b) The BLU of the NC system(b) The BLU of the NC system(c) The frequency of pulses transmitted by the encoder.

Ans. 3 m/min, 10 micron, 5000 pps3 , , 5 pp

IES 2011 Conventionalh bl f h d b d h hThe table of a CNC machine is driven by a Lead screw which

is rotated by a DC servomotor. A digital encoder which emitsis rotated by a DC servomotor. A digital encoder which emits

1000 pulses per second is mounted on the lead screw as a

feedback device. If the lead screw pitch is 6 mm and motor

t t t fi drotates at 500 rpm, find

1 Basic length Units of the system1. Basic length Units of the system

2. Linear velocity of the table.

3. Frequency of pulses generated by the feedback device.

Ans. 50 microns, 3 m/min, 1000 pps [5 Marks]For-2013 (IES, GATE & PSUs) Page 82

GATE – 2010 (PI)F CNC bl h lid l h i l iFor a 3 –axes CNC table, the slide along the vertical axisof the table is driven by a DC servo motor via a leadscrew‐ nut mechanism. The lead screw has a pitch of 5mm. This lead screw is fitted with a relative(incremental) circular encoder. The basic length unit(BLU) of the slide along the vertical axis of the table is(BLU) of the slide along the vertical axis of the table is0.005 mm. When the table moves along the vertical axisb th di b f l t dby 9 mm, the corresponding number of pulses generatedby the encoder is(a) 1400 (b) 1800 (c) 4200 (d) 9000BB

Statement for Linked Answers questions: S‐1I h f d d i f P i P i l CNCIn the feed drive of a Point‐to‐Point open loop CNCdrive, a stepper motor rotating at 200 steps/rev drives atable through a gear box and lead screw‐nut mechanism(pitch = 4 mm, number of starts = 1).(p 4 , )The gear ratio = is given by U =h (d b l l f l

speedrotationalInputspeedrotationalOutput

41

The stepper motor (driven by voltage pulses from a pulsegenerator) executes 1 step/pulse of the pulse generator.The frequency of the pulse train from the pulsegenerator is f = 10,000 pulses per minute.generator is f 10,000 pulses per minute.

( )GATE – 2008 Q‐1 (Statement in S‐1) Th B i L h U i (BLU) i h blThe Basic Length Unit (BLU), i.e., the tablemovement corresponding to 1 pulse of the pulsegenerator, is(a) 0 5 microns (b) 5 microns(a) 0.5 microns (b) 5 microns(c) 50 microns (d) 500 micronsB

( )GATE – 2008 Q‐2 (Statement in S‐1) A t i i t difi ti t h th BLUA customer insists on a modification to change the BLUof the CNC drive to 10 microns without changing thet bl d Th difi ti b li h d btable speed. The modification can be accomplished by

Ans (a) It is correct ans Most books will give (c) ForAns. (a) It is correct ans. Most books will give (c). Forsame table speed, ‘f ’ must be half.

GATE – 2009 (PI)The total angular movement (in degrees) of a lead‐screw

with a pitch of 5.0 mm to drive the work‐table by a

di f i NC hi idistance of 200 mm in a NC machine is

( ) (b) 88 ( ) 6 (d)(a) 14400 (b) 28800 (c) 57600 (d) 72000

AA

IAS 2010 MainIAS‐2010 MainIn open‐loop NC system the shaft of a stepping motor isp p y pp gconnected directly to the lead screw x‐axis of themachine table. The pitch of the lead screw is 3.0 mm.machine table. The pitch of the lead screw is 3.0 mm.The number of step angles on the stepping motor is 200.

Determine how closely the position of the table can becontrolled assuming that there are no mechanical errorscontrolled, assuming that there are no mechanical errorsin the positioning system.

Also, what is the required frequency of the pulse trainand the corresponding rotational speed of the steppingand the corresponding rotational speed of the steppingmotor in order to drive the table at a travel rate of 100mm/min? [8 Marks]mm/min? [8‐Marks]

GATE ‐ 1992I i i f NCIn a point‐to‐point type of NC system(a) Control of position and velocity of the tool is( ) p yessential(b) Control of only position of the tool is sufficient(b) Control of only position of the tool is sufficient(c) Control of only velocity of the tool is sufficient(d) Neither position nor velocity need be controlled

B

GATE ‐ 2006NC i i l fNC contouring is an example of(a) Continuous path positioning( ) p p g(b) Point‐to‐point positioning( ) Ab l i i i(c) Absolute positioning(d) Incremental positioning( ) p g

A

GATE‐2005Which among the NC operations given below are continuous path operations? continuous path operations? Arc Welding (AW) Milling (M)Drilling (D) Punching is Sheet Metal (P)Laser Cutting of Sheet Metal (LC) Spot Welding (SW)Laser Cutting of Sheet Metal (LC) Spot Welding (SW)

(a) AW, LC and M (b) AW, D, LC and M( ) d (d) d(c) D, LC, P and SW (d) D, LC, and SW

AA


IES ‐ 2000A i (A) Th i f NC d illi hiAssertion (A): The axis of an NC drilling machinespindle is denoted as z‐axis.Reason (R): In NC machine tool, the axisperpendicular to both x‐ and y‐axis is designated asperpendicular to both x and y axis is designated asz‐axis( ) h d d d ll d h(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true A

IES ‐ 1996A i (A) N i ll ll d hiAssertion (A): Numerically controlled machineshaving more than three axes do not exist.Reason (R): There are only three Cartesiancoordinates namely x‐y‐zcoordinates namely x y z.(a) Both A and R are individually true and R is the


IES ‐ 2003 S‐1Whil iWhile part programmingin CNC machines, theinput of dimensionalinformation for the toolpath can be given in theabsolute co‐ordinateabsolute co‐ordinatesystem or in incremental

di t t Thco‐ordinate system. Theabove figure shows the

b f ll d b hroute to be followed by thetool from O to C, i.e., O ‐ A‐ B ‐ C.

dIES – 2003 Contd.. From S‐1 If i l di i d hIf incremental co‐ordinates system is used, the co‐ordinates of each point A, B and C are

(a) A: X 5.0, Y 10.0 (b) A: X 5.0, Y 10.0B: X 20 0 Y5 0 B: X 25 Y 15 0B: X 20.0, Y5.0 B: X 25, Y 15.0C: X 10.0, Y 10.0 C: X 35, Y 5.0

(c) A: X 10.0, Y 5.0 (d) A: X 10.0, Y 5.0B X Y B X YB: X 15.0, Y 25.0 B: X 5.0, Y 20.0C: X 15.0, Y 35.0 C: X 10.0, Y 10.0

AA

GATE ‐2012 Same Q in GATE 2012 (PI)GATE ‐2012 Same Q in GATE‐2012 (PI)

A CNC vertical milling machine has to cut aA CNC vertical milling machine has to cut astraight slot of 10 mm width and 2 mm depth by acutter of 10 mm diameter between points (0 0)cutter of 10 mm diameter between points (0, 0)and (100, 100) on the XY plane (dimensions in

) Th f d d f illi i / imm). The feed rate used for milling is 50 mm/min.Milling time for the slot (in seconds) is(a) 120 (b) 170 (c) 180 (d) 240

B

( )GATE – 2007 (PI)Th i t l t i CNC hi t lThe interpolator in a CNC machine controls(a) Spindle Speed (b) Coolant flow(a) Spindle Speed (b) Coolant flow(c) Feed rate (d) Tool change

CC

GATE ‐ 2004D i h i f CNC bl kDuring the execution of a CNC part program blockN020 G02 X45.0 Y25.0 R5.0 the type of tool motion will45 5 5 ypbe(a) Circular Interpolation clockwise(a) Circular Interpolation – clockwise(b) Circular Interpolation ‐ counter clockwise(c) Linear Interpolation(d) R id f d(d) Rapid feed

A

GATE ‐ 2010I CNC bl k N G G X ZIn a CNC program block, N002 G02 G91 X40 Z40…,G02 and G91 refer to(a) Circular interpolation in counterclockwise directionand incremental dimensionand incremental dimension(b) Circular interpolation in counterclockwise direction

d b l dand absolute dimension(c) Circular interpolation in clockwise direction and(c) C cu a te po at o c oc se d ect o a dincremental dimension(d) Ci l i t l ti i l k i di ti d(d) Circular interpolation in clockwise direction andabsolute dimensionC

IES ‐ 2009Interpolation in the controller refers to control of

h h f h f ll hwhich one of the following in a CNCmachine?

( ) L di / l di f j b hi(a) Loading/unloading of jobs on machine

(b) L di / l di f t l f th t l h(b) Loading/unloading of tools from the tool changer

(c) Axes of machine for contouring(c) Axes of machine for contouring

(d) Coolant and miscellaneous functions on machine(d) Coolant and miscellaneous functions on machine

CC


GATE ‐ 2001I NC hi i i h l h bIn an NC machining operation, the tool has to bemoved from point (5, 4) to point (7, 2) along acircular path with centre at (5, 2). Before starting theoperation, the tool is at (5, 4). The correct G and Mp , (5, 4)code for this motion is(a) N010 G03 X 0 Y2 0 I 0 J2 0(a) N010 G03 X7.0 Y2.0 I5.0 J2.0(b) N010 G02 X7.0 Y2.0 I5.0 J2.0(c) N010 G01 X7.0 Y2.0 I5.0 J2.0(d) N G X Y I J(d) N010 G00 X7.0 Y2.0 I5.0 J2.0B

GATE ‐ 2005Th l f NC hi h lThe tool of an NC machine has to move along acircular arc from (5, 5) to (10,10) while performing anoperation. The centre of the arc is at (10, 5). Whichone of the following NC tool path commandsg pperforms the abovementioned operation?(a) N010G02 X10 Y10 X Y R(a) N010G02 X10 Y10 X5 Y5 R5(b) N010G03 X10 Y10 X5 Y5 R5(c) N010G01 X5 Y5 X10 Y10 R5(d) N G X Y X Y R(d) N010G02 X5 Y5 X10 Y10 R5D

GATE ‐ 2000I fi i h hi i f i l d i i hIn finish machining of an island on a casting withCNC milling machine, an end mill with 10 mmdiameter is employed. The corner points of theisland are represented by (0, 0), (0, 30), (50, 30), andp y ( , ), ( , 3 ), (5 , 3 ),(50, 0). By applying cutter radius rightcompensation the trajectory of the cutterwill becompensation, the trajectory of the cutterwill be(a) (‐5, 0), (‐5, 35), (55, 35), (55, ‐5), (‐5, ‐5)(b) (0, ‐5), (55, ‐5), (55, 35), (‐5, 35), (‐5, ‐5)(c) (5 5) (5 25) (45 25) (45 5) (5 5)(c) (5, 5), (5, 25), (45, 25), (45, 5), (5, 5)(d) (5, 5), (45, 5), (45, 25), (5, 25), (5, 5)B

GATE ‐ 2009

C

IES ‐ 1993 A 'bl k' f i f i i N C hiA 'block' of information in N.C. machine programmeans(a) One row on tape(b) A word comprising several rows on tape(b) A word comprising several rows on tape(c) One complete instruction(d) One complete program for a job

c

IES ‐ 1996I l i d i fIn manual programming and tape preparation for aNC drilling machine, the spindle speed was codedas S 684 (using the magic‐three code). The spindlespeed in rpmwill bep p(a) 684(b)(b) 68.4(c) 840(c) 840(d) 6840A

IES ‐ 1995 Match List I with List II and select the correct answerMatch List I with List II and select the correct answerusing the codes given below the lists:

List I List IIList I List II(A function connected (Associated parameter)with NCm/c tool)with NCm/c tool)A. Interpolation 1. Tape preparationB Parity check 2 Canned cycleB. Parity check 2. Canned cycleC. Preparatory function 3. DrillingD P i t t i t t l C t iD. Point to point control 4. Contouring

5. Turning [A]C d A B C D A B C DCode:A B C D A B C D(a) 4 1 2 3 (b) 4 1 2 5( ) (d)(c) 5 1 3 2 (d) 1 4 3 2

IAS‐2011 MainIn an NC drilling operation the tool tip is at location (In an NC drilling operation, the tool tip is at location (‐100, 0, 100). The datum (0, 0, 0) is left hand lower corner

f f h k i hi h i lon top surface of the workpiece, which is rectangular(300 mm x 300 mm x 1.5 mm thick). A thru' hole of 10mm diameter is t o be drilled in the centre of theworkpiece. Using only rapid positioning and linearworkpiece. Using only rapid positioning and linearinterpolation functions, write the program blocks, inabsolute modeabsolute mode.Assume permitted cutting speed = 32 m/min and feedrate = 150 mm/min. [10‐Marks]

IFS 2011IFS 2011I NC hi h t i th f th itIn NC machine, what is the purpose of the parity

check ? What is the function of Data Processingcheck ? What is the function of Data Processing

Unit (DPU) and Control Loop Unit (CLU) of MCU.p

How is Feed Rate Number (FRN) expressed ? What

is indirect feedback ?

[10‐marks]


IES ‐ 1998Whi h f h f ll i h l fWhich of the following are the rules ofprogramming NCmachine tools in APT language?1. Only capital letters are used2 A period is placed at the end of each statement2. A period is placed at the end of each statement3. Insertion of space does not affect the APT wordSelect the correct answer using the codes given below:( ) d (b) d(a) 1 and 2 (b) 2 and 3(c) 1 and 3 (d) 1 aloneD

IES‐2008Name the four types of statements in a complete APTpart program. Prepare part program for geometrydescription of the contour shown in the figure below:p g

[15‐Marks]30 40

Y

R 20L3L2

20C1

R 2135°

3

L180L4

R 20L5

C2

P1R20

P1P2X

IES‐2007Prepare part using APT language formilling the contourshown in Fig. in a single pass. [20‐Marks]

110R30

DCR30

QB

110

++120

E ++40

R40

++ 40100A F

PMaterial : M S.

8 mm

IES‐2006Prepare part program to machine the contour shown inthe figure using APT on CNCmilling machine.

[15‐Marks]R30 5

•

•

R20

R30

•

80

100 mm

200 60 50

200 mm

Material: MS Thickness: 8.0 mm

Home WorkWrite a complete part program in APT for machiningWrite a complete part program in APT for machiningthe product which is given in the diagram. Thickness ofth k i i 6 All di i ithe workpiece is 6 mm. All dimensions are in mm.

[15]

IES 2011 ConventionalState the method of defining line segment of

tt ti i APT f tcutter motion using APT program format.

[5 Marks][5 Marks]

IES ‐ 1997Whi h f h f ll i lid fWhich of the following are valid statements forpoint to point motion of the tool in APT language?1. GO/TO/............2 GO DLTA/2. GO DLTA/............3. GO/TO, ……….Select the correct answer using the codes given below:( ) d (b) d(a) 1 and 2 (b) 2 and 3(c) 1 and 3 (d) 1, 2 and 3C

IES ‐ 1995I APT l h i i i lIn APT language, the cutter motion in incrementalcoordinatemode is addressed as(a) GO/TO/.....(b) GO/TO(b) GO/TO.....(c) GO DLTA/....(d) GO FWD/...CC

GATE 2008 (PI)GATE ‐2008 (PI)Suppose point P in APT programming is coded by statementSuppose point P1 in APT programming is coded by statementP1 = POINT/XSMALL, INTOF, LN1, CR1h d d hThe coded geometric situation without causing error is

BFor-2013 (IES, GATE & PSUs) Page 86

IES ‐ 2012Th fi i f b i l i h The configuration of a robot using a telescoping arm that can be raised or lowered on a horizontal pivot mounted on a rotating base is called(a) Polar (a) Polar (b) Cylindrical(c) Cartesian coordinate (d) Jointed arm(d) Jointed arm

B

IES 2011Trajectory of a robot mean :

(a) Path traced by the end effectors

(b) f b(b) Kinematics of Robot

( ) R b t j i t(c) Robot joints

(d) Robot programming(d) Robot programming

A

IES 2010Consider the following statements:Consider the following statements:Good dynamic performance is usually difficult to achievei b hi h i b bin robots which contain a rotary base because

1. Position, speed and acceleration of the other joints causevariations in the reflected torque and moment of inertia.

2. The moment of inertia reflected at the base depends upon thep pweight of the object being carried.

3 The moment of inertia reflected at the base also depends upon3. The moment of inertia reflected at the base also depends uponthe distance between the base axis and the manipulated object.

Which of the above statements is/are correct?Which of the above statements is/are correct?(a) 1, 2 and 3 (b) 2 and 3 only(c) 1 only (d) 1 and 3 only B

IES ‐ 2006Whi h f h f ll i i h hi d b iWhich one of the following is the third basiccomponent of robots besides power supply andcontrol (memory) console?(a) Software (b) Coaxial cable(a) Software (b) Coaxial cable(c) Mechanical unit arm (d) Microcomputer

CC

IES ‐ 2000C id h f ll i h i i f bConsider the following characteristics of a robot:1. The tip of the robot arm moves from one point to

another with its in‐between path not being defined.2. It can be used for drilling holes at difference points in a2. It can be used for drilling holes at difference points in a

workpiece.It can be used for V butt joint welding between two3. It can be used for V butt joint welding between twopoints.

4. The memory capacity required for its control unit is low.Which of these are the characteristics associated with a pointpto point robot?(a) 1 and 2 (b) 1 3 and 4(a) 1 and 2 (b) 1, 3 and 4(c) 1, 2 and 4 (d) 2, 3 and 4 C

IES ‐ 2006Whi h i b d ib CAM h l ?Which item best describes a CAM technology?(a) Geometric modeling (b) Documentation( ) g ( )(c) Drafting (d) Numerical control

D

ISRO‐2011ISRO‐2011I CAM " P i " fIn CAM, " Part programming" refers to

(a) Generation of cutter location data

(b) On‐line Inspection

(c) Machine Selection

(d) Tool Selection A

IES ‐ 2012Programmable automation is suitable for

(a) Low production volume and large varieties of parts

(b) Low production volume and small varieties of parts

( )(c) High production volume and small varieties of parts

(d) Hi h d i l d l i i f (d) High production volume and large varieties of parts

AA

IES ‐ 1996Whi h f h f ll i i l h d?Which of the following pairs are correctly matched?1. CNC machine…… Post processorp2. Machining centre….Tool magazine

DNC FMS3. DNC…………. FMS(a) 1, 2 and 3 (b) 1 and 2( ) , 3 ( )(c) 1 and 3 (d) 2 and 3

AA


IES ‐ 2006 Flexible manufacturing allows for:

(a) Tool design and production

(b) Automated design

( )(c) Quick and inexpensive product change

(d) Q li l(d) Quality control

AA

IES ‐ 2004C id h f ll i h i iConsider the following characteristics:1. Single machine toolg2. Manual materials handling system

C l3. Computer control4. Random sequencing of parts to machines4 q g pWhich of the above characteristics are associated withfl ibl f t i t ?flexible manufacturing system?(a) 1, 2 and 3 (b) 1 and 2(c) 3 and 4 (d) 2, 3 and 4AA

IES ‐ 2012R k d l i li d f i Rank order clustering as applied to manufacturing automation is(a) A technique of identifying process sequence in production of a componentproduction of a component(b) A just in time (JIT) method(c) An approach of grouping the machines into cells in an FMS systema S syste(d) A tool to generate bill of materials

CC

NTMMNTMM


IES ‐ 2012Which of the following processes has very high material

l ffremoval rate efficiency?

( ) El b hi i (a) Electron beam machining

(b) El t h i l hi i(b) Electrochemical machining

(c) Electro discharge machining (c) Electro discharge machining

(d) Plasma arc machining(d) Plasma arc machining

BB

GATE ‐ 2006A th i th i i d fArrange the processes in the increasing order oftheirmaximummaterial removal rate.Electrochemical Machining (ECM)Ultrasonic Machining (USM)g ( )Electron BeamMachining (EBM)Laser Beam Machining (LBM) andLaser Beam Machining (LBM) andElectric Discharge Machining (EDM)(a) USM, LBM, EBM, EDM, ECM(b) EBM LBM USM ECM EDM(b) EBM, LBM, USM, ECM, EDM(c) LBM, EBM, USM, ECM, EDM(d) LBM EBM USM EDM ECM [D](d) LBM, EBM, USM, EDM, ECM [D]

IES ‐ 2007C id h f ll i i l i hConsider the following statements in relation to theunconventional machining processes:1. Different forms of energy directly applied to thepiece to have shape transformation or material removalpiece to have shape transformation or material removalfrom work surface.

l b h k d h l2. Relative motion between the work and the tool isessential.3. Cutting tool is not in physical contact with workpiecepiece.(a) 1 and 2 only (b) 1, 2 and 3 only(c) 2 and 3 only (d) 1 and 3 only D

IES ‐ 2009 Whi h f h f ll i i iWhich one of the following statements is correct inrespect of unconventional machining processes?(a) The cutting tool is in direct contact with the job(b) The tool material needs to be harder than the job(b) The tool material needs to be harder than the jobmaterial(c) The tool is never in contact with the job(d) There has to be a relative motion between the tool(d) There has to be a relative motion between the tooland the jobC

IAS ‐ 2002M t h Li t I (P ) ith Li t II (T lMatch List I (Processes) with List II (Tolerancesobtained) and select the correct answer using the codesgiven below the Lists:given below the Lists:

List I List II(P ) (T l b i d)(Processes) (Tolerances obtained)A. Plasma Arc machining 1. 7∙5 micronsB. Laser Beam machining 2. 25 micronsC. Abrasive Jet machining 3. 50 micronsC. Abrasive Jet machining 3. 50 micronsD. Ultrasonic machining 4. 125 microns [C]

Codes:A B C D A B C DCodes:A B C D A B C D(a) 4 1 3 2 (b) 3 2 4 1( ) (d)(c) 4 2 3 1 (d) 3 1 4 2


ISRO‐2009The machining process in which the work picce is

dissolved into an electrolyte solution is called

(a) Electro‐chemical machining

(b) Ultrasonic machining

(c) Electro‐discharge machining

(d) Laser machining

A

PSUECM cannot be undertaken for(a) steel(a) steel(b) Nickel based superalloy(c) Al2O3(d) Titanium alloy(d) Titanium alloy

C

PSUPSUCommercial ECM is carried out at a combinationCommercial ECM is carried out at a combinationof

( ) l l hi h(a) low voltage high current(b) low current low voltage( ) g(c) high current high voltage(d) l l l(d) low current low voltageA

IAS‐2011 MainIAS‐2011 MainWhat is the principle of electro‐chemicalWhat is the principle of electro chemicalmachining (ECM)?Wh h d d di d fWhat are the advantages and disadvantages ofECM over conventional drilling?Comment on the surface finish and the accuracy ofthe ECMthe ECM.

[20‐Marks]

lExampleU i ECM / i f i k i Using ECM remove 5 cm3/min from an iron workpiece, what current is required?Atomic weight of iron 56, density 7.8 g/cm3 valency, 2

GATE‐2008 (PI)In an electro chemical machining (ECM) operation, asquare hole of dimensions 5 mm x 5 mm is drilled in asquare hole of dimensions 5 mm x 5 mm is drilled in ablock of copper. The current used is 5000 A. Atomicweight of cupper is 63 and valency of dissolution is 1.Faraday’s constant is 96500 coulomb The materialFaraday s constant is 96500 coulomb. The materialremoval rate (in g/s) is

(a) 0.326 (b) 3.260 (c) 3.15 x 103 (d) 3.15 x 105

B

( )GATE – 2011 (PI)Whil i i l f i ( i i h 6While removing material from iron (atomic weight = 56,valency = 2 and density = 7.8 g/cc) by electrochemicalmachining, a metal removal rate of 2 cc/min is desired.The current (in A) required for achieving this material( ) q gremoval rate is(a) 896 0 (b) 14 93(a) 896.07 (b) 14.93(c) 448.03 (d) 53764.29

AA

lExampleC l l h i l l d hCalculate the material removal rate and theelectrode feed rate in the electrochemicalmachining of an iron surface that is 25 mm × 25 mmin cross‐section using NaCl in water as electrolyte.g yThe gap between the tool and the workpiece is 0.25mm The supply voltage is 12 V DC The specificmm. The supply voltage is 12 V DC. The specificresistance of the electrolyte is

l3Ω c m

For iron, Valency, Z = 2Atomic weight, A = 55.85Atomic weight, A 55.85Density, = 3.53 mm/min37860 kg / m

l ( )Example (GATE‐2009)El h i l hi i i f d Electrochemical machining is performed to remove material from an iron surface of 20 mm x 20 mm under the following conditions:

Inter electrode gap = 0 2 mmInter electrode gap = 0.2 mmSupply Voltage (DC) = 12 VSpecific resistance of electrolyte = 2 cmAtomic weight of Iron = 55 85

Ω

Atomic weight of Iron = 55.85Valency of Iron = 2Faraday's constant = 96540 CoulombsThe material removal rate (in g/s) is [0 347]The material removal rate (in g/s) is [0.347]


lExampleComposition of a Nickel super alloy is as follows:Composition of a Nickel super‐alloy is as follows:Ni = 70.0%, Cr = 20.0%, Fe = 5.0% and rest TitaniumCalculate rate of dissolution if the area of the tool is 1500mm2 and a current of 1000 A is being passed through themm and a current of 1000 A is being passed through thecell. Assume dissolution to take place at lowest valancyf th l tof the elements.

1.41 mm/min

GATE ‐ 2008A researcher conducts electrochemical machining

( ) b ll (d k ) f(ECM) on a binary alloy (density 6000 kg/m3) of iron

(atomic weight 56 valency 2) and metal P (atomic(atomic weight 56, valency 2) and metal P (atomic

weight 24, valency 4). Faraday's constant = 96500weight 24, valency 4). Faraday s constant 96500

coulomb/mole. Volumetric material removal rate of

the alloy is 50 mm3/s at a current of 2000 A. The

percentage of themetal P in the alloy is closest to

(a) 40 (b) 25 (c) 15 (d) 79 [B]

lExampleTh l h i l hi i f i f h iThe electrochemical machining of an iron surface that is25 mm × 25 mm in cross‐section using NaCl in water aselectrolyte. The gap between the tool and the workpieceis 0.25 mm. The supply voltage is 12 V DC. The specific5 pp y g presistance of the electrolyte is 3 Ωcm.Estimate the electrol te flo rate Specific heat of theEstimate the electrolyte flow rate. Specific heat of theelectrolyte is given as 0.997 cal/g˚C. The ambient

d h l l b ltemperature is 35˚C and the electrolyte boilingtemperature, is 95˚C.pDensity, = 7860 kg/m3

lExampleI ECM i f i ilib i fIn ECM operation of pure iron an equilibrium gap of 2mm is to be kept. Determine supply voltage, if the totalovervoltage is 2.5 V. The resistivity of the electrolyte is 50Ω‐mm and the set feed rate is 0.25 mm/min.5 /

13.73 Volt3.73 o t

( )GATE – 2007 (PI)Whi h f th f ll i ditiWhich one of the following process conditionsleads to higher MRR in ECM process?g p(a) higher current, larger atomic weight(b) higher valency, lower current(c) lower atomic weight lower valency(c) lower atomic weight, lower valency(d) higher valency, lower atomic weight( ) g y, g

A

GATE – 2012 (PI) Linked S‐1In an EDM process using RC relaxation circuit, a 12 mmdiameter through hole is made in a steel plate of 50 mmg p 5thickness using a graphite tool and kerosene asdielectric Assume discharge time to be negligibledielectric. Assume discharge time to be negligible.Machining is carried out under the following conditions:

R i ΩResistance 40 ΩCapacitance 20 μFp μSupply voltage 220 V

h lDischarge voltage 110 VThe time for one cycle, in milliseconds, isThe time for one cycle, in milliseconds, is(a) 0.55 (b) 0.32 (c) 0.89 (d) 0.24 A

GATE – 2012 (PI) Linked S‐2In an EDM process using RC relaxation circuit, a 12 mmdiameter through hole is made in a steel plate of 50 mmg p 5thickness using a graphite tool and kerosene asdielectric Assume discharge time to be negligibledielectric. Assume discharge time to be negligible.Machining is carried out under the following conditions:

R i ΩResistance 40 ΩCapacitance 20 μFp μSupply voltage 220 V

h lDischarge voltage 110 VAverage power input (in kW) isAverage power input (in kW) is(a) 0.373 (b) 0.137 (c) 0.218 (d) 0.500 C

IES ‐ 2000C id th f ll i t t tConsider the following statements:In electrochemical grinding,1. A rubber bonded alumina grinding wheel acts as thecathode and the workplace as the anode.p2. A copper bonded alumina grinding wheel acts as thecathode and the work piece as the anodecathode and the work piece as the anode.3. Metal removal takes place due to the pressure

li d b th i di h lapplied by the grinding wheel.4. Metal removal takes place due to electrolysis.Which of these statements are correct?(a) 1 and 3 (b) 2 and 4(a) 1 and 3 (b) 2 and 4(c) 2 and 3 (d) 1 and3 [B]

GATE ‐ 2001I ECM h i l l i dIn ECM, thematerial removal is due to(a) Corrosion( )(b) Erosion( ) F i(c) Fusion(d) Ion displacement( ) p

[D][D]


GATE ‐ 1997S l i l l f ECM i f llSelection electrolyte for ECM is as follows:(a) Non‐passivating electrolyte for stock removal and( ) p g ypassivating electrolyte for finish control(b) Passivating electrolyte for stock removal and non(b) Passivating electrolyte for stock removal and non‐passivating electrolyte for finish control(c) Selection of electrolyte is dependent on currentdensityde s ty(d) Electrolyte selection is based on tool‐ workl t delectrodes

[D]

GATE ‐ 1992The twomain criteria for selecting the electrolyte in

El t h i l M hi i (ECM) i th t thElectrochemical Machining (ECM) is that the

electrolyte shouldelectrolyte should

(a) Be chemically stable( ) y

(b) Not allow dissolution of cathode material

(c) Not allow dissolution of anode material

(d) Have high electrical conductivity

Ans. (a, d)

GATE ‐ 1997Inter electrode gap in ECG is controlled by

(a) Controlling the pressure of electrolyte flow

(b) Controlling the applied static load

( )(c) Controlling the size of diamond particle in the wheel

(d) C lli h f h k i(d) Controlling the texture of the work piece

CC

IES ‐ 2002A i (A) I ECM h h f h i i hAssertion (A): In ECM, the shape of the cavity is themirror image of the tool, but unlike EDM, the toolwear in ECM is less.Reason (R): The tool in ECM is a cathodeReason (R): The tool in ECM is a cathode.(a) Both A and R are individually true and R is the


IES ‐ 1997Which one of the following processes does not

lcause tool wear?

( ) Ul i hi i(a) Ultrasonic machining

(b) El t h i l hi i(b) Electrochemical machining

(c) Electric discharge machining(c) Electric discharge machining

(d) Anode mechanical machining(d) Anode mechanical machining

BB

IES 2011 ConventionalDiscuss the effects of insufficient dielectric and

l l l h l d helectrolyte circulation in the inter‐electrode gap on the

Electric Discharge machining and Electro ChemicalElectric Discharge machining and Electro Chemical

Machining process respectively. [5 Marks]Machining process respectively. [5 Marks]

IES 2009 ConventionalIES 2009 Conventionali. What is the principle of metal removal in EDMi. What is the principle of metal removal in EDM

process?ii D ib h i h h h l f k hii. Describe the process with the help of sketch.iii. List advantages and limitations of the system.g y

[ 15 marks]

GATE ‐ 1994El i di h hi i i ffi iElectric discharge machining is more efficientprocess than Electrochemical machining forproducing large non‐circular holes.The above statement isThe above statement is(a) True(b) False(c) Cant say(c) Cant say(d) Insufficient data

AA

IES ‐ 2012S (I) I El Di h M hi i (EDM)Statement (I): In Electro Discharge Machining (EDM)process, tool is made cathode and work piece anodeStatement (II): In this process if both electrodes are made ofsame material, greatest erosion takes place upon anode, g p p(a) Both Statement (I) and Statement (II) are individuallytrue and Statement (II) is the correct explanation oftrue and Statement (II) is the correct explanation ofStatement (I)(b) B th St t t (I) d St t t (II) i di id ll(b) Both Statement (I) and Statement (II) are individuallytrue but Statement (II) is not the correct explanation ofS (I)Statement (I)(c) Statement (I) is true but Statement (II) is false(d) Statement (I) is false but Statement (II) is true [A]


GATE ‐ 2004Th h i f i l l i EDMThe mechanism of material removal in EDMprocess is(a) Melting and Evaporation(b) Melting and Corrosion(b) Melting and Corrosion(c) Erosion and Cavitation(d) Cavitation and Evaporation

A

GATE ‐ 2003A l d k i i EDMAs tool and work are not in contact in EDM process(a) No relative motion occurs between them( )(b) No wear of tool occurs( ) N i d d i l i(c) No power is consumed during metal cutting(d) No force between tool and work occurs( )

DD

GATE ‐ 1999I El Di h M hi i (EDM) h l iIn Electro‐Discharge Machining (EDM), the tool ismade of(a) Copper (b) High Speed Steel(c) Cast Iron (d) Plain Carbon Steel(c) Cast Iron (d) Plain Carbon Steel

A

GATE‐2010 (PI)Keeping all other parameters unchanged, the tool

wear in electrical discharge machining (EDM) wouldwear in electrical discharge machining (EDM) would

be less if the tool material has

(a) high thermal conductivity and high specific heat

(b) high thermal conductivity and low specific heat

(c) low thermal conductivity and low specific heat

(d) low thermal conductivity and high specific heat

A

GATE ‐ 2007I l di h hi i (EDM) if hIn electro discharge machining (EDM), if thethermal conductivity of tool is high and the specificheat of work piece is low, then the tool wear rateand material removal rate are expected to beprespectively(a) High and high (b) Lo and lo(a) High and high (b) Low and low(c) High and low (d) Low and high

DD

GATE ‐ 2005A i i i bl k fA zigzag cavity in a block ofhigh strength alloy is to befinish machined. This can becarried out by usingy g(a) Electric discharge machining(b) l h l h(b) Electro‐chemical machining(c) Laser beam machining(c) ase bea ac g(d) Abrasive flow machining

AA

IES ‐ 2005Whi h f h f ll i i / d l iWhich of the following is/are used as low wearingtool material(s) in electric dischargemachining?(a) Copper and brass(b) Aluminium and graphite(b) Aluminium and graphite(c) Silver tungsten and copper tungsten(d) Cast iron

C

GATE‐ 2000D h l d illi f ll di iDeep hole drilling of small diameter, say 0.2 mm isdonewith EDM by selecting the tool material as(a) Copper wire (b) Tungsten wire(c) Brass wire (d) Tungsten carbide(c) Brass wire (d) Tungsten carbide

B

GATE – 2009 (PI)A titanium sheet of 5.0 mm thickness is cut by wire

– cut EDM process using a wire of 1.0 mm diameter.

A uniform spark gap of 0.5 mm on both sides of the

ire is maintained during cutting operation If thewire is maintained during cutting operation. If the

feed rate of the wire into the sheet is 20 mm/minfeed rate of the wire into the sheet is 20 mm/min,

the material removal rate (in mm3/min) will be

(a) 150 (b) 200 (c) 300 (d) 400 [B]


GATE ‐2010 (PI)Ultrasonic machines, used in material removal processes,

require ultrasonic transducers. The transducers works on

different working principles One of the working principlesdifferent working principles. One of the working principles

of such ultrasonic transducers is based on

(a) eddy current effect (b) Seebeck effect

(c) piezo‐resistive effect (d) piezo‐electric effect

[D]

GATE ‐ 1994Ul i hi i i b h b fUltrasonic machining is about the best process formaking holes in glass which are comparable in sizewith the thickness of the sheet.The above statement isThe above statement is(a) True(b) False(c) Cant say(c) Cant say(d) Insufficient data

AA

IES 2011USM has good machining performance for :

(a) Al

(b) Steel

(c) Super alloys

(d) Refractory material

D

GATE ‐ 1993In ultrasonic machining process, the material

l ll b h h f l hremoval rate will be higher formaterials with

( ) Hi h h (b) Hi h d ili(a) Higher toughness (b) Higher ductility

( ) L t h (d) Hi h f t t i(c) Lower toughness (d) Higher fracture strain

CC

GATE ‐ 1992 I Ul i M hi i (USM) h i lIn Ultrasonic Machining (USM) the materialremoval rate would(a) Increase(b) Decrease(b) Decrease(c) Increase and then decrease(d) decrease and then increaseith i i i di t f th b iwith increasing mean grain diameter of the abrasive

material.

CC

IES ‐ 2009B hi h f h f ll i hBy which one of the following processes themetering holes in injector nozzles of diesel enginescan be suitably made?(a) Ultrasonic machining(a) Ultrasonic machining(b) Abrasive jet machining(c) Electron beam machining(d) Chemical machining(d) Chemical machining

B

IES ‐ 2006During ultrasonic machining, the metal removal is

h d bachieved by

( ) Hi h f dd(a) High frequency eddy currents

(b) hi h f d(b) high frequency sound waves

(c) Hammering action of abrasive particles(c) Hammering action of abrasive particles

(d) Rubbing action between tool and workpiece(d) Rubbing action between tool and workpiece

CC

IAS ‐ 1996During ultrasonic machining, the metal removal is

ff d b haffected by the

( ) H i i f b i i l(a) Hammering action of abrasive particles

(b) R bbi ti b t t l d k i(b) Rubbing action between tool and workpiece

(c) High frequency sound waves(c) High frequency sound waves

(d) High frequency eddy currents(d) High frequency eddy currents

CC

IFS‐2011IFS‐2011Write the advantages limitations and applications of Write the advantages, limitations and applications of

electron beam machining. What is the safety problem g y p

connected with EBM?

[5‐Marks]


GATE 2012 Same Q in GATE 2012 (PI)GATE ‐2012 Same Q in GATE‐2012 (PI)In abrasive jet machining, as the distance betweenIn abrasive jet machining, as the distance betweenthe nozzle tip and the work surface increases, thematerial removal ratematerial removal rate(a) increases continuously.(b) decreases continuously.(c) decreases becomes stable and then increases(c) decreases, becomes stable and then increases.(d) increases, becomes stable and then decreasesD

IAS‐2011 MainIAS‐2011 MainSt t th h i f tti b b i j tState the mechanism of cutting by abrasive jet.

What are the advantages and disadvantages of What are the advantages and disadvantages of

AJM ? Mention two applications. AJM ? Mention two applications.

[10‐Marks][ ]

IFS‐2011IFS‐2011What are the disadvantages of abrasive jet machining? What are the disadvantages of abrasive jet machining?

Write some of its applications.pp

[5‐Marks]

GATE ‐ 1992M h h f ll i i h h iMatch the following components with the appropriatemachining processes:Component Process(A) Square hole in a high strength alloy (1) Milling(B) Square hole in a ceramic component (2) Drilling(C) Blind holes in a die (3) ECM(C) Blind holes in a die (3) ECM(D) Turbine blade profile on high strength alloy(4) Jig boring

(5) EDM(5) EDM[B] (6) USM

Codes:A B C D A B C D(a) 4 1 2 3 (b) 5 6 1 3(c) 4 2 1 3 (d) 3 1 2 4

GATE 2011GATE 2011Match the following non – traditional machiningg gprocesses with the corresponding material removalmechanism:

Machining process Mechanism of material removalP. Chemical machining 1. Erosiong

Q. Electro – chemical machining

2. Corrosive reactionmachiningR. Electro – discharge machining

3. Ion displacementmachiningS. Ultrasonic machining 4. Fusion and vaporization

(a) P – 2, Q – 3, R – 4, S – 1 (b) P – 2, Q – 4, R – 3, S – 1(c) P – 3, Q – 2, R – 4, S – 1 (d) P – 2, Q – 3, R – 1, S – 4 [A]

GATE ‐ 2007M t h th t it bl f t i f Match the most suitable manufacturing processes for the following parts. Parts Manufacturing ProcessesP. Computer chip 1. Electrochemical Machiningp p gQ. Metal forming dies and moulds

2 Ultrasonic Machining2. Ultrasonic MachiningR. Turbine blade 3. Electro‐discharge

h [ ]Machining [A]S. Glass 4. Photochemical Machining4 g

Codes:P Q R S P Q R S(a) 4 3 1 2 (b) 4 3 2 1(a) 4 3 1 2 (b) 4 3 2 1(c) 3 1 4 2 (d) 1 2 4 3

GATE ‐ 1998 Li I Li IIList I List II(A) ECM (1) Plastic shear( ) ( )(B) EDM (2) Erosion/Brittle fracture(C) USM ( ) C i i(C) USM (3) Corrosive reaction(D) LBM (4) Melting and vaporization( ) (4) g p

(5) Ion displacement [B]( ) l h d d l(6) Plastic shear and ion displacement

Codes:A B C D A B C DCodes:A B C D A B C D(a) 4 1 2 3 (b) 5 4 2 4( ) ( )(c) 4 2 1 3 (d) 3 1 2 4

IES ‐ 2008M h Li I i h Li II d l hMatch List‐I with List‐II and select the correct answerusing the code given below the lists:

List‐I List‐II(Unconventional machining process) (Basic process)(Unconventional machining process) (Basic process)A. Electro polishing 1. ThermalB El h i l hi i M h i lB. Electrochemical machining 2. MechanicalC. Abrasive jet machining 3. Electrochemicalj g 3D. Electrical discharge machining 4. Chemical [A]

Code:A B C D A B C DCode:A B C D A B C D(a) 4 3 2 1 (b) 2 1 4 3(c) 4 1 2 3 (d) 2 3 4 1

IES – 1998, ISRO‐2009M h Li I (M hi i ) i h Li IIMatch List‐I (Machining process) with List‐II(Associated medium) and select the correct answerusing the codes given below the lists:

List‐I List‐IIList I List IIA. Ultrasonic machining 1. KeroseneB. EDM 2. Abrasive slurryC ECM 3 VacuumC. ECM 3. VacuumD. EBM 4. Salt solution [B]

Code:A B C D A B C D(a) 2 3 4 1 (b) 2 1 4 3(a) 2 3 4 1 (b) 2 1 4 3(c) 4 1 2 3 (d) 4 3 2 1For-2013 (IES, GATE & PSUs) Page 94

IES ‐ 2005 Match List I (Machining Process) with List IIMatch List I (Machining Process) with List II(Application) and select the correct answer using thecode given below the Lists:code given below the Lists:List I List IIA EDM 1 Holes & cavities in hard & brittle materialsA. EDM 1. Holes & cavities in hard & brittle materialsB. LBM 2. Micro‐drilling & micro‐welding of

materialsC. USM 3. Shaping of hard metals or reshaping of

cemented carbide toolsD. ECM 4. Shaping of cemented carbide dies and

punches [C]Codes:A B C D A B C D(a) 4 1 2 3 (b) 3 2 1 4(c) 4 2 1 3 (d) 3 1 2 4

IES ‐ 2003M t h Li t I (M t i l ) ith Li t II (M hi i ) dMatch List I (Materials) with List II (Machining) andselect the correct answer using the codes given belowthe Lists:the Lists:

List I List II(M i l ) (M hi i )(Materials) (Machining)A. Machining of conducting materials 1. ECMB. Ruby rod 2. EDMC. Electrolyte 3. USMC. Electrolyte 3. USMD. Abrasive slurry [D] 4. LBM

Codes:A B C D A B C DCodes:A B C D A B C D(a) 4 2 1 3 (b) 4 2 3 1( ) (d)(c) 2 4 3 1 (d) 2 4 1 3

IES ‐ 2003A ti (A) W t j t hi i hi hAssertion (A): Water jet machining uses highpressure and high velocity water stream which actslik d t i th t i llike a saw and cuts a narrow groove in thematerial.Reason (R): The force required for cutting isgenerated from sudden change in the momentumof thewater stream.(a) Both A and R are individually true and R is thecorrect explanation of Aco ect e p a at o o(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false( ) [ ](d) A is false but R is true [A]

IAS ‐ 2002Whi h f h f ll i i i NOT lWhich one of the following pairs is NOT correctlymatched?(Unconventional (Application)machining method)machining method)(a) Electric discharge : Machining of electrically

conductive materials(b) Laser beam : Micromachining(b) Laser beam : Micromachining(c) Plasma arc : Faster cutting of hard materials(d) Electron beam : Faster metal removal rate[D][D]

IAS ‐ 1999M h Li I (U i l hi i ) i hMatch List I (Unconventional machining process) withList II (Typical application) and select the correct

h d b l h lanswer using the codes given below the lists:List I List II

A. Electro discharge machining 1. Drilling micro holes invery hard metalsvery hard metals

B. Electro chemical machining 2. Drilling holes in glass[ ]C. Ultrasonic machining 3. Die sinking [D]

D. Laser beam machining 4. Machining contoursg 4 gCodes:A B C D A B C D(a) 4 2 3 (b) 3 4 2(a) 4 2 3 1 (b) 3 4 1 2(c) 4 3 2 1 (d) 3 4 2 1

IES ‐ 2004M t h Li t I (M hi i ) ith Li t IIMatch List I (Machining processes) with List II(Operating media) and select the correct answer usingthe codes given below the Lists:the codes given below the Lists:

List I List IIA Ab i j hi i Di l iA. Abrasive jet machining 1. DielectricB. Electron beam machining 2. ElectrolyteC. Electro‐chemical machining 3. Abrasive slurryD. Electro‐discharge machining 4. VacuumD. Electro discharge machining 4. Vacuum

5. Air [A]Codes:A B C D A B C DCodes:A B C D A B C D(a) 5 4 2 1 (b) 4 5 2 1( ) (d)(c) 4 2 3 5 (d) 2 5 3 4

IES ‐ 1999M t h Li t I ith Li t II d l t th tMatch List‐I with List‐II and select the correct answerusing the codes given below the Lists:

Li I Li IIList‐I List‐IIA. Die sinking 1. Abrasive jet machiningB. Debarring 2. Laser beam machiningC. Fine hole drilling (thin materials) 3. EDMg ( ) 3D. Cutting/sharpening hard materials [C]

4 Ultrasonic machining4. Ultrasonic machining5. Electrochemical grinding

C d A B C D A B C DCode:A B C D A B C D(a) 3 5 4 1 (b) 2 4 1 3(c) 3 1 2 5 (d) 4 5 1 3

GATE ‐ 2004T i l hi i ti t b f d h dTypical machining operations are to be performed on hard‐to‐machine materials by using the processes listed below.Choose the best set of Operation‐Process combinationsChoose the best set of Operation Process combinations

Operation ProcessP Debarring (internal surface) 1 Plasma Arc MachiningP. Debarring (internal surface) 1. Plasma Arc MachiningQ. Die sinking 2. Abrasive Flow MachiningR Fine hole drilling in thin sheets 3 Electric DischargeR. Fine hole drilling in thin sheets 3. Electric Discharge

MachiningS Tool sharpening 4 Ultrasonic MachiningS. Tool sharpening 4. Ultrasonic Machining

5. Laser beamMachining6 Electrochemical Grinding6. Electrochemical Grinding

(a) P‐1 Q‐5 R‐3 S‐4 (b) P‐1 Q‐4 R‐1 S‐2( ) P Q R S 6 (d) P Q R S 6 [D](c) P‐5 Q‐1 R‐2 S‐6 (d) P‐2 Q‐3 R‐5 S‐6 [D]

Jigs and FixturesJigs and Fixtures

By S K MondalFor-2013 (IES, GATE & PSUs) Page 95

IES ‐ 2007A di h i i l f l i i ji dAccording to the principle of location in jigs andfixtures, how many degrees of freedom are to beeliminated to have a body fixed in space?(a) 3(a) 3(b) 4(c) 5(d) 6(d) 6

D

GATE ‐ 2005Wh i i l i d d lWhen 3‐2‐1 principle is used to support and locate athree dimensional work‐piece during machining,the number of degrees of freedom that arerestricted is(a) 7(b)(b) 8(c) 9(c) 9(d) 10

CC

GATE ‐ 2001h d f l i i ji fi ld3‐2‐1 method of location in a jig or fixture would

collectively restrict the workpiece in n degrees offreedom, where the value of n is(a) 6(a) 6(b) 8(c) 9(d) 12(d) 12

C

IES 2011In the 3‐2‐1 principle of fixture 3 refers to number of :(a) Setups possible(b) Cl i d(b) Clamps required(c) Positions on primary face( ) p y(d) Locating positions

Ans. (d) Locations on primary face not positions on s. (d) oca o s o p a y ace o pos o s othe primary face.

IES – 1999A i (A) S h i l h d lAssertion (A): Spherical washers are used to locatethe job in the fixtures.Reason (R): 3‐2‐1 principle should be adopted tolocate the joblocate the job.(a) Both A and R are individually true and R is the


IFS‐2011IFS‐2011What are the functions of jig ? Draw a jig to machineWhat are the functions of jig ? Draw a jig to machine

four holes in a plate. What are two reasons for notp

having drill bushings actually touching the workpiece

? What is a duplex fixture ?

[10‐marks]

IES – 1998, 1999Di d i l i i d i fi bDiamond pin location is used in a fixture because(a) It does not wear out( )(b) It takes care of any variation in centre distancebetween two holesbetween two holes(c) It is easy to clamp the part on diamond pins(d) It is easy to manufacture

B

IES ‐ 2009A l h i t i l d ill d h lA lever having two precisely drilled holes, onesmaller than the other, has to be located in a fixture

i h d d d d l f f thusing hardened and ground plugs for furthermachining in relation to the holes. Select the

t th d f l ti th l f th icorrect method of locating the lever from the givenalternatives.(a) Using two hardened and ground plugs, the smallerone having flats machined on each side(b) Using two hardened and ground plugs(c) Using one hardened and ground plug and one V‐(c) Using one hardened and ground plug and one V‐block(d) U i t V bl k A(d) Using two V‐blocks A

IES ‐ 1995If the diameter of the hole is subject to considerable

h f l d f hvariation, then for locating in jigs and fixtures, the

pressure type of locator used ispressure type of locator used is

(a) Conical locator(a) Conical locator

(b) Cylindrical locator(b) Cylindrical locator

(c) Diamond pin locator(c) Diamond pin locator

(d) Vee locator A( )


IES ‐ 2005M t h Li t I (A El t f Ji d Fi t ) ith Li tMatch List I (An Element of Jigs and Fixtures) with ListII (Associating System) and select the correct answerusing the code given below the Lists:using the code given below the Lists:

List I List IIA B h Milli fiA Bush 1. Milling fixtureB. Setting block 2. Turning fixtureC. Diamond pin 3. Radial locationD. V‐block 4. Cylindrical locationD. V block 4. Cylindrical location

5. Drill jigs [C]Codes:A B C D A B C DCodes:A B C D A B C D(a) 5 4 3 1 (b) 3 1 2 4( ) (d)(c) 5 1 3 4 (d) 3 4 2 1

IES‐2011IES‐2011With the help of a neat sketch explain the working ofWith the help of a neat sketch, explain the working of

the diamond pin locator.p

[5‐marks]

IES ‐ 2000Match List I (Components used in jigs and fixtures) with List IIMatch List I (Components used in jigs and fixtures) with List II(Their functions) and select the correct answer using the codesgiven below the Lists:

List I List IIA. Jack pin 1. To guide the drill bit during machiningJ p g g gB. V‐locator 2. For easy removal of the work piece from the

jig or fixture after the machining operationjis over

C. Bushes 3. To locate the circular orsemicircular objects in a jig or fixture

D. Ejectors 4. To locate work piece whose dimensions aresubject to variations [B]

Code: A B C D A B C D(a) 3 4 1 2 (b) 4 3 1 2(c) 3 4 2 1 (d) 4 3 2 1

IES ‐ 1995Match List I with List Ii and select the correct answer using theMatch List I with List Ii and select the correct answer using thecodes given below the lists:List I (Task) List II (Recommendation)A. Three components in a straight 1. Clampwith a

floating pad.line should worked in one loadingline should worked in one loading

B. Unloading of clamp element from jig is essentialg p j g2. Quick action nut

C. Clamping of rough surfaces 3. Cam clampd f h l f l lD. Need for heavy clamping force 4. Equalising clamp

5. Strap clamp [D]Code: A B C D A B C DCode: A B C D A B C D

(a) 5 2 3 4 (b) 4 2 1 5(c) 1 4 2 3 (d) 4 1 5 3(c) 1 4 2 3 (d) 4 1 5 3

IES ‐ 2005Whi h f h f ll i i h i ifiWhich one of the following is the most significantproperty to be considered in the selection ofmaterial for the manufacture of locating pins anddrill jig buses used in jigs and fixtures?j g j g(a) Wear resistance (b) Elasticity( ) Sh h (d) l h(c) Shear strength (d) Tensile strength

A

IES ‐ 1996A i (A) A k i i h h hi dAssertion (A): A workpiece with rough un‐machinedsurface can be located in a jig or fixture on threesupporting points.Reason (R): Indexing is made accurate byReason (R): Indexing is made accurate bysupporting on three points.( ) h d d d ll d h(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of Acorrect explanation of A(c) A is true but R is false(d) A is false but R is true C

IES ‐ 1996C id h f ll iConsider the following statements:The cutter setting block in a milling fixtureg g

1. Sets the cutting tool with respect of two of its surfaces.Li i h l l i d b h d i2. Limits the total travel required by the cutter duringmachining.

3. Takes location from the location scheme of thecomponentcomponent.

(a) 1,2 and 3 are correct (b) 1 and 2 are correct(c) 2 and 3 are correct (d) 1 and 3 are correctDD

IES ‐ 1993Th fl i i i f h h ldi fi iThe floating position of the holding fixture in arotary transfer device is used to(a) Improve the accuracy of location(b) Reduce the tendency to over index(b) Reduce the tendency to over index(c) Reduce the cycle time(d) Improve upon the acceleration and decelerationcharacteristicscharacteristics

D

( )GATE – 2009 (PI)Match the following:Match the following:

Device FunctionP. Jig 1. Helps to place the workpiece in the same

position cycle after cyclep y yQ. Fixture 2. Holds the workpiece onlyR Cl H ld d i i h k iR. Clamp 3. Holds and positions the workpieceS. Locator 4. Holds and positions the workpiece and4 p p

guides the cutting tool during a machiningoperation

(a) P‐1, Q‐3, R‐1, S‐2 (b) P‐1, Q‐2, R‐3, S‐4

operation

(c) P‐1, Q‐4, R‐3, S‐2 (d) P‐4, Q‐3, R‐2, S‐1 DFor-2013 (IES, GATE & PSUs) Page 97

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