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Manufacturing TechnologyII- Nov/Dcc-2011 1

i 11 " i i i i i i ~ m

^ Question Paper Code : SS459 )

B.F.JB.Tcch. DEGREE EXAMINATION, NOVEMBER / DECEMBER 2011

Fourth Semester Mechanical Engineering

ME 2252 - MANUFACTURING TECHNOLOGY - n (Regulation 2008)

(Common to PTME 2252 - Manufacturing Technology II for.B.E. (Part-Timc)

1'hird Semester Mechanical Engineering Regulation 2009)

Time : Three hours Maximum : 100 marks

Answer All questions PART A - (10 X 2 = 20 marks)

1. State any two situations where positive rate angle isrecommended during turning.

2. Name any two reasons for (lank wear in cutting tools3. List the different taper turning methods.4. Mention any two limitations of a centre lathe.5. What is deep hole drilling? State its applications.6. What is climb milling? Mention its advantage.7. Wliat are the types of surface gnnders?8. Mention any two advantages of gear hobbing.

9: Distinguish between point to point and continuous path systems.

10. What do you mean by machining centre W.R to N.C machines ?PART B(5 X16--80 marks)

11. (a)(i) Discuss the advantages and limitations of the followingcutting tool materials.

(1) Cemented carbides,,(2) Cubic Boron Nitride.

Also state the desirable characteristics of a cutting tool material.


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Manufacturing Technology -11. Nov/Dec-2 Ori 1 2

(8)

(ii) WiUltLe help of sketches, expla in the following types of chips

produced durin g metal machining.

(1 KJootLnuotrs chips.

(2) Coi!ilLnuous chips with bui! t-up-cdgc. (S)

Or

(b) Explain the types and applications of di fferem types o-f cutting tools.

(S')

(tii) Enumerate the factors that effect the cutting temperature during m achi

ning, (4)

12. (a)(i) Describe the special featuresofa turret lathe,, with a linesketch. Also mcnti on any two advantages ot' it (8)

(it) Describe the operation of the Swiss type automatic i athe, with suitable

sketches. .

Or

(b)(i) Explain the following, with suitable sketches.

0 )Turret Indexing mechanism

(2)Bar feed mechanism (8)

(ii) Sketch and describe the thread cutting operation in an engine la the

using compound slide.


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15. (a)(i) Explain the following terms with reference to CNC machines!

(1) Tool Length compensation(2)Cutter raidus compensation (8)

(ii) With a help of an example explain the differences between point to

point and continuous path type of num erically controlled machine

tools. (8)

Or

(b) (i) Explain the worktn g of a NC mac hine tool with the help of a diagram.

Also state any two advantages and limitations of NC machines.(8i)

(if) Discuss the fit notions of the folio wing with reference toNC machine.

(1) Linear bearings13.


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(b)(i) With a neat sketch, describe the -working principle of abrasive jet

machining. State its product applications. )

(ii) Explain the working principle and product appli cations of the following

processes :

(1) Honing(2)Lapping (8)

15. (a)(i) Explain the following lenu* with jcfeicucc to CNC machines.(1) Tool Length compensation(2) Cutter raidus compensation(8)

With a help of an example explain the differences, between point to

point and continuous path type of numerically controlled machine

tools. (8)

Or

(b) (i) Explain the working of a NC machine t ool wit h the help of a diagram.

Also state any two advantages and Limitations ofNC machines.

(8 )

(ii) Discuss the funct ions of the following wi th reference to NC machine.fl> Linear bearings


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Manufacturing Technology - LI- Nov,"Dee -2011 8

Part-A

1. State any two. situations where positive rate angle is recommended duringturning.

The slope given to tool face in such a way that it should be away from

thecuttingedg.es and slant towards thcback/sidcofthe tool. In most of the applicat

ions, positive rate angle is provided on the tool face.

2. Name any two reasons for Flank wear in catting tools F lank wear occurs, when machining of bn tile material likecost iron is

done.

When flank wear increases, the frictional heat will cause high temperature of

the tool at the cutting edge which decreases the hardness and causes failure

of the tool.

It results in a rough machined surface.

3. List the different taper turning methods?v Form tool Methods.

> Tai 1 stock ser over method

*> Compound Rest Methods

Taper turning attachment method.

4. Mention any two Limitations of a Centre lathe-> Only one tool can be used in the normal course

*> Large setting lime of die job is required.


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The idle times involved in setting and movement of the tools between tbe

cuts in targe.

> It requires skilled! labours and the accuracy of the parts is leas.

It cannot be used for mass production for making identical parts.

5. What is deep hole drilling? State its applications.Deep hole d rilling is a machining operation where holes are drilled whose

depth exceeds the normal drill size. These operations are carried out at high speed

and low feed.Applications of deep hole drilling are;

> Used for drilling deep holes in rifle travels.

> Used for drill ing c rank shafts etc...

6. What is climb milling? Mention its advantage:Climb milling is otherwise called as down milling process. In this process

the workplace is Fed in the same direction as that ofthc cutters tangential velocity.

Advantages of Climb milling, are;

> The clamping force required is less.

> This process produces belter finish and dimention accuracy. > Coolant can

be easily Fed.

> Removal ofthc chap as easier.

7. What are the types of Surface griudersI* Horizontal spindle Reciprocating Table surface grinder.

I* Horizontal spindle Rotary Tabic surface grinder.

*> Vertical spi ndle Reciprocating Table surface grinder.

> Vertical spindle Rotary Table surface grinder.

8. Mention any two advantages of gear hobbing> It is easy to control the tooth spacing, head and tooth profile, v Setting and

operation of bobbing machine is simple.

*>Long shafts and splines can be accommodated in hobbing machine.

All types of spur and helical gears can be cut oo both metaU and non

metals.> Large number of similar gear held on a mandrel can be cut at

a time. The production rate is comparatively higher.


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Manu factoring Tcchncl ogy - II- Nov/Dec-201 L 8

10. Whit do you meinby machining centre w.r toN.C machines?In machine centre a Automatic Tool changer (ATC) is used for performing the

following operations like milling, drilling. Reaming, Boring, lapping etc... I he

machining centre has two (or) more table named as pallets. Automatic pallet changer

(APC) centre is used and time will be reduced.

There are three types of machining centres:

2 Hoii^uubjJ SpuiiJtc iiudcluiiJiicriiisc.

> Vertical spindle machining centre.

Universal machining centre.Prt - B

U-a


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ManufecturingTcchDology 0- h'ov/Dcc-2011 9

while machining steels. Inorder to improve resistance to cratering, alloyed tungsten

carbides arc used with additi ons of carbides of titanium and molybdenum-etc.

Titanium carbide improves the hot hardness and reduces the tendency of chips to

weld to tbc tool.

(2) Cubic B-oron Nitride :CBN is next in hardness only to diamond fKnoop hardness 4-700 kgt'mg-). It is

not a natural maternal but produced in tbc laboratoiy using a high temperature/high

pies sure process similar to the making of artificial diamond. CUN' is less reactive

with materials like hardncd steels hard chill cast iron., and nickel base and cobalt

base super alloys. This is very expensive, 10 lo 20 times than of a conventional

abrasive such as AT.OrCBN is a combination of Boror. and Nitrogen.

Characteristics of an cutting, tool materials'.

The material must remain harder than work material at elevated temperature.

>The material must withstand excessive wear even through the relative hardness

of the tool-work materials changes > The material must nave sufficient strength and

dvcriluy to wiih stand shocks and Vibrations and to prevent breakage.


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Manufacturing Technology - II* Nov/Dec-2011 10

> Ilcc coefficient of friction at the chip tool interface must rcmatn low for

minimum WCAT and reasonable surface finish.

The cost and easiness- offribractson should be within reasonable limits.

11. (a) (ii) With the help of a sketches explain the following, types of chips

produced daring metal machining.

(I) Continuons chips, (2) Continuous chips with built-up edge.

(I) Continuous Chips:

During cutting of ductile

material, a continuous ribbon 1

ike chip is produced due to Use

jues.vui c of the tool cutting

edge in compression and shear.

These types of chips are in the form of a long coil and have the same thickness

throughout the length. The advantage of continuous

chip formation are1 good surface finish improves the

tool Ii fe and less power consumption. The disposal of

the chi p i s not a easy task in contimtouschips The

following condition favours the formation Of

continuous chip; Ductile maternal lilcccarbon steel, aluminium, copper etc...,

smaller depth of cut. Higher cutting Speed. Large rake angle, sharp cutting edge,

proper cutting fluid, and low friction between tool face and the chips.


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Manufacturing Technology - II- 'Nov/Dec-2011

causes the chip material to weld itself to the tool face near the nose as shown in fig.

This is called built-up edge ".

Formation of a built-up edge in continuous chip is a transient and not stable

phenomenon. The accumulated built-up of chip material will then break away, part

adhering to the underside of the chip and pari to the work piece. Thus, the p rocess

gi ves rise t o a poor surface finish on the machined surface and accelerated wears

on the tool face.

However, this type of chips having some advantages, the one important favour

of it is that, the. rake face of the tool protected from wears due to moving chips and

the action of heat. It may result the increasing of tool life. .

Shear plane

Work

Segmental chip

The following conditions favour the formation of dtsconti nuou.v chips:

Low cutting speed.

*S> Small rake angle.

Coarsefeed.

Strong adhesion between chips and tool face.

O Insufficient cutting fhiid. Large uncut thickness.

11. (b) (i) With the help of a sketch show crater wear and fEank wear on a

cutting tool.


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Manufacturing Technology II- Nov/Dec-2011 12

Flank Wear

thus its also called as edge wear. Friction, abrasion, adhesions are the main

causes for this type of wear. Flank wear is a flat worn out portion behind die cutting

edge. The worn out region of the flank is known as wear land. This wear takes place

when machining brittle material I ike cast iron. It also occurs when the feed is less

than

15mmi'revolution. "When the wear land increases, tlie frictional heat will cause

excessive temperature of the tool at the culting edge thereby decreasing its hardness

rapidly and hcnoc catastrophic failure of the tool will occur. Flank wear results ill a

rough machined surface.

Crater Wear

The face of the tool is always contacted with the chip. The chip slides over the

face of the tool. Due to tbc pressure of the sliding chip, the tool face wears out

gradually. A cavity, is formed on the tool face. The cavity is called crater. This type

of wear is known as crater wear. The major tendency of this type of wear is abrasion

between the chip and the face of the tool. When cratering becomes excessive, the

cutting edge may break from the tool.

Cratering is commonly occurred while machininga ductile material which

produces continuous chips. Diffusion of metal may be one of the causcso-f this type

of wear. The maximum depth of the crater is usually a measure of the amount of the

crater wear. The tool life due 10crater wear can be determined by fixing the ratio of

width o f crater to its depth

The tool wear i sgenerally classified as follows.


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Manufacturing Technology- II- Mov .'I)cc-201 i 13

(iii) Nose wear11. (b) (ii) Explain the types and applications of different type* of cuttingcools:

a) Depending upon the number of cutting edges the cutting tools used in metalcutting are classified as follows:

(I) Single point cutting tool


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*fr Cutting speed is 3too high

> Poor surface finish on the cutting face of the tool *S* Worn (or) Incorroclly

ground culting tool > Formation of a built up edge on cut ting face of the cool

v FriciJOBbetween tool and work piece

12. (a) (i) Describe the special features of a turret lathe, with a line sketch.Also mention any two advantages of It.

Capstan and Turret Jathes arc the two types of semi-automatic lathes. The

construction and. working principle of both the lathes are oneand the same. But they

differ in applications. The turret lathe is used tor heavy jobs whereas the capstanlathe is used for light and smalljobs.

The main parts of turret lathes arc

1 Bed2 Head stock3. Turret head and saddle '1.Cross slide


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Turret lathe

12, () (HJ Describe the operation o f the Swiss type automatic lathe, with

suitable sketches.

This type of automatic lathe is suitable for small but long and slender parts like

parts of wrist watches. There is a distinct d rffercncc between the conventional

automatic ladies and Swiss type automatic lathes in the latter. Uhe work is fed

against the tool Tlte head stock carrying the bar slock moves back and forth forproviding the feed movement nt the longitudinal direction. H cncc, this type of

automatic lathe is a Iso called a sliding head automatic lathe.

This machine is used for producing long accurate parts of small diameter (2 to

25mnf). In this, the parts can be machined to an accuracy of0.005mm to O.OI25nim

1 here may be as many, as Five cross slides in the case of a utomatic lat lie.

However, prpducti vity-w ise, the conventional automatic lathes arc superior for

short work pieces. The advantage of a sliding head automatic tathc is that long sl-

cndcr work pieces can be machined with very yood surface finish accuracy and

concentricity i n sliding


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Manufacturing Technology-II- Nov.'Doc-2G 11 16

head automatic lathes, further the Swiss type automatic lathes arc capable of

completely machine certain types of parts which may require second and thirdoperations in conventional automatic

head stock Tool bracket

Motor

Swloc type ecrew cutting machine

Bar stock


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Manufacturing Technology-II- Nov/Dcc-2011 17

*** slams

Working principle:

The bar stock is bcLd in the rotating spindle by a collets chuck. Head stock

slides along the bed ways with the rotating bar stock.

This head stock movement gives longitudinal feed to the work. All the tools in

the tool slides remove material from the work piece at the same time the tool in the

feed base attachment may also do operations like dnlling. After Lhc work piece is

machined, the head stock slides back to the original position. One revolution of the

cams ha ft produces one component.

Most o f the turning and forming operations ar e done by the tools held on the

(horizontal) front and rear tool slides The vertical tool slidesarernainlyusedfor

undercutting chamfering, knurling cutting off.

Advantages of Swiss type screw machine:

0. It is used to manufacture turning of small parts.1. It has five tool slides-


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Manufacturing Technology-II- Nov.'Doc-2G 11 18

S. Wide range of speeds is available.

4. It is rigid in construction.5. Micrometer tool setting is possible .6. Intcrchangcabilityofcatns is possible.7. Simple dcssgn of cams is enough.8. Tolerance of0.005 to 0.0125mm is obtained.9. Numerous working stations are available.It consists of four major purls:

1. The sliding hcadstock through which the bar stock is passed and gripped bya. carbide-lined guide bush

2. The camshaft which controls the bar stock and cutting tool movements.The tool bracket which supports five tool slides

and a bush for stock.

4.Auxiliary* attachments for performing various operations such a s knurling,drilling, tappin g, screwing, slotting, recessing etc.

The descriptions of various parts are given below:

1. Sliding hcadstock:This hcadstock has a collect. The haT stock is held in the collect. The hcadstock

slides along the guide ways of the bed. A bell cam connected to the camshaft

controls this sliding motion.

2. Tool bracketThe tool bracket is mounted on the bed way near the hcadstock. *!hc tool

bracket supports 4 or 5 tool slides It also has a bush for supporting and guiding the

bar stock. Two slides are positioned horizontally i.e. One at the front and the other

at the rear The other slides are arranged above these -slides. All the slides can move

back and forth.

These slides are actuated independently by sets of rocker arms and plate cams.

Plate cams are fitted to the camshaft.


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Manufacturing Technology - D- Nov/Dee-2011 19

Tool bracket

3. Feed baseThe feed, base vs

mounted at the right

hand sick of the

headstock. This can

move a long, the bed.

Using this; attachment,

operations like drilling,

boring, thread culting

etc are done. The

movement of the feedbase is controlled by

the plate cam fitted to

the camshaft.

4. CamshaftThe ca mshaft is mounted at the front of the machine. It has a bell cam at the left

end. This controls the sliding movement of the headstock . Plate cams fitted at the

center of the shaft controls the movement of tbc tool slides. Plate C3m at thexight

end ofthe camshaft controls the movement of the feed base

1. BedBed as the base part of the lathe. It is a bo* type which is- made of cast iron,

(iui.de ways on tbc top of the bed has been provided accurately. Cross slide and

narrcl head are mourned on these guide ways. The bed should be strong and rigid to

withstand heavy loads, force and vibrations during m achini ng task.

Infeed cam arm


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Manufacturing Technology' 11- Nov,rDcc-2011 2

2. Cross slide

The two types of cross slides are

1. Reach over type2. Side hung type

(I) Reaches over type:

ft is mounted, on the bed guide ways in between 'aeadslock and turret which is

also supported by lower rail. The cross slide has two tool posts. One is at the front

end having four faces of square turret for mounting the tools Fxcb tool can be

indexed by 90 stop bars are provided for controlling the motion of each tool which

can be indexed automatically along with square turret for the next machining

opttratirw

The tool post can move both in perpendicular and parallel to t he spindle 3xis.

Mostly power feed is used for movement of the tool post.

In rear tool post, the parting-off tool is clamped in inverted position to make the

direction of rotation of workpiece anticlockwise wtth re spec t to tool mov ernent.


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Manufacturing Techno logy - II- Nov/Dec-201 1 21

by simply pushing a button or pulling a lever. The required speed of the next

operation can also be selected advance. At the end ofthc first operation, the lever isactuated to rotate the spindle at the selected speed without stopping the machine.

4. Tor ret head A turret head haa. a hexagonal block having six faces with a bore for mounting

six or more than six tool s at a t ime. The four threaded boles on these faces arc used

to accommodate the tool holders. The turret head is mourned on the ram fitted with

turret slides longitudinally on a saddle.

- Ram of capstan lathe

The ram is actuated either by hard or power. The forward movement of die ram is

controlled by a -preset or adjustable stop To index the cutting too!, the ram or turret

is returnee to its starting position for tripping the stops. The tripped stops arc locked

in position by locking nuts.

$>Wi H> tee


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M anufaclunni? Technology Q Nov,T>^c 20l I

Advantages of turret lathes:

> Rate of production is high > It has wider range of speed > Cost of labour

is less

*> More than one operation can be performed at the same rime.

Large Dumber of tools can be held

Heavier and large work piece chucking can be done.

Tra%orse tor turret position 4

Travwrri* lor turret podtioo I

Hexagonal turret

Saddle of turret In the


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Manufacturing Technology - II- Nov/Dec- 2011

In a capstan lathe, the turret head is mounted on a ram which slides on a

saddle, it can be positional on a lathe bed ways and clamped well.

Ln a turret lathe, the turret head is mounted on the saddle itself which slides

on the bed ways during machining.lt is mainly used in turret lathe.

12, {!>) (i) Kxplain the following with suitable sketches

(1) Turret indexing mechanism

An indexing mechanism for turret is shown in figures. There is small vertical

spindle < 1) fixed on the saddle. At the top to the spindle, the turret head (2) is

mounted just be low the turrtt.head on the same spindlie. 3 circular index plate (3)

having six slots, a bevel gear (4) and a ratcher{6) mounted on the saddle which

locks the index plane. This prevents the rota tion of turret during the rnach ining

operation. A pin fitted on the plunger projects out of tbe housing.

ft* of

plunger (7) rides, over the sloping surface of the cam. So the plunger is released

from the .groove of the index


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Manufacturing TechnologyU- No v/Dec-201!plate. Now the spring loaded pawl engages the ratchet groove and rotate it. The in

dcx plate and the turret spindle rotates through 1 /6 of a revolution. The pin (5)drops of the cam and hence the plunger locks at the index psat e at the next

groove. Thus the turret is indexed automatically.

There is a shaft (11) ha ving a bevel pinion (12) arc one end. At its other end.

a circular plate is connected. Six adjustable stop rods (I 3) arc fitted to this

circular plute. The bevel pinion meshes with the bevel gear When the turret

rotates, the bevel pinion will also rotate. And hence the circular stop plate is a Iso

indexed by l/6ofu revolution.

2. Bar feed mechanism:In turret and capstan lathes, the bar is fed automatically. This bar feeding is

done without stopping the lathe to reduce the production time.

The bar stock passes through a bar chuck of the feeding mechanism and the

hollow spindle of the lathe. The bar is held by the collect chuck. The bar chuck is

fitted to the bar by set screws. The bar chucks rotates is a sleeve along with the

bar. The loose sleeve is housed ina sliding. The slider brakci can slide over 3

sliding bar. The

Bar feeding mechanism


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Manufecmnng Technology 11- JNov/Dcc-201 i 24s.hd ing bracket is attached to one end of a chain. A weigh! is suspended at the

other end or the chain as shown in figure. This arrangements exerts a constantforce on the bar chuck towards right.

When the bar is released by the colled, the force due to suspended weight will

feed the bar towards right. This feeding lakes place towards nght. This feeding

takes place till the end of baT puli against the bar stop held in the turret. Then the

collect as closed.

In this way the bar is fed without stopping the machine. After a number of

such feedings the bar chuck wilL approach the rear end of the bead stock. Now

the bar chuck is released from the bar and brought to the left extreme position.

Then it is screwed on to the bar

12* (b) (ii) Sketch and describe the thread cutting operation in an engine

lathe using compound slide:

0-Major Diameter, d Core Ola Meter, P Pflch

(c) Sample Gear Train 4b) Thread C-uttingi Cper?*c-n

e-C&r*QQ

Thread cutting mechanism

*. Tl^eadLH Thr ead


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Manufacturing Technology - H- Nov/Dec-201 I 26The principle of thread cutting is to produce helical groove on a cylindrical or

conical surface by feeding the tool longitudinally. The job is held between centersor by a chuck. The toot used is called threading tool. The rotation of the lead

screw is used to transverse the tool along the worn to produce screw threads. The

half nut makes the carriage to engage or di sen gage the lead screw whiLe cutting

threads. The speed of job is reduced to one-third or onc-forth of the job speed

used in turning operation. The work is held between centers and turned s ize of

the majoT diameter of the threa d to be then change gears of correct sizes are

calculated as below and fitted between the lathe spindle and the lead screw.

Thread cutting:

Thread cutting is the process of p-rodu cing a helical groove on a cylindricalor conical surface. The necessary condition for cutting screw is that in one revol

ution of the spindle (wor k) the tool traverse a distance equal to She pitch of the

thread to be cut. This is achieved .by a gear train between the lead screw and the

lathe spindle. The gear ratio for cutting screw threads may be giVen as.

Driver "Fitch of the JobGear raho = =

Dnven Pitch of the I cad screw

Every lathe will be equipped with a quick change gearbox Therefore in such

lathes gear box is not provided a suitable set of gears has to be found out and

mounted at the proper position for cutting threads of different pitches. Setting up

of lathe for su-ch worit includes proper holding of the job, concentric with the

lathe centers, setting of too! at proper height and mounting of the calculated

change gears at proper location.

The lead screws get its motion with the help of change gears. The stud gear

(of the change gears) meshes with, the reversing gear whic h get s motion through

the spindle in the head stock.


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Manufacturing Techno-logy - JI- Nov/Dec-201113, (a) (i) With a neat sketch, describe tbc working principle of a jig boring

machine. State its application

Jig boring machine

A jig boring machine is a precision boring machine used for boring accurate

holes, al proper centre-to-centrc distances. It is specially designed machine tool

for the preci sion location and production of holes needed in jigs, fixtures, dies

and templates. The machining accuracy of holes produced by this machine tool

lies with in a range of 0.0025nmt. Buill in precision measuring devices for axis

movement is another specialty of this machine. This machine is also used for

prototype production of accurate parts, production of parts in small quantities

where investment in tooling ts not desirable, work pieces like dnll jigs and parts

requiring very high accuracy. In appearance and construction. 3 jig boring

machine resembles a vertical milling machine but it is more rigid and accurate.

Tbc spindle and other parts of this machine are very rigid to resist deflection.

There are mainly two types of jig boring machines.

1. Single vertical column type2. Planer type.Jig boring operations:

In addition to drilling, boring and milling, many other operations such as

lacing counter boring, countersinking and trepanning can be performed on jigboring machines

Single vertical column type jig boring machine

A block diagram of this type is shown in the fig. This is the most extensively,

usod jig boring machine.

It consists of the following parts

(Ij Bod (ii)Colttuin (iii) Spindlehead

Table (v) Saddle


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The member that supports the machine is known as bed. It is a box shaped

casting made of cast iron. To provide more rigidly. J is provided with stiffened

ribs.

It supports the column sadd le and the whole machine and houses all the

electrical controls of the machine. The column is a hollow vertical cast iron

structure that supports the spindle head; guide ways and vertical hand traverse of

the spindle head. The spindle can slide up and down on the vertical guide ways of

the column. There is a quill attached to the spindle head. The spindle housing is

fitted at the bottom of the quill, The spindle housing is made of a special metal

called invar. 'Hie machine spindle rotates in accurate antifriction bearing,

A saddle moves on the horizontal guide ways over the "bed. The table is fined

over the saddle. The table can be adj usted cross-wise. Generally the table is

provided with T-slots at the lop surface for clamping the work piece. The saddle

permits the work to move longitudinally. Longitudinal and traverse motion, to the

table and saddle are given by separate electrical motor fiued inside the bed Rapid

traverse of tabic and saddle is affected by a clutch Verniers are pro sided for

setting the tabie by hand. The various machine operations arc controlled by means

of pick up drives

Application:

It is used in precision tool room applications such a s j ig. fixture, template,

dies, casting and other components. It can be used for carryiaigout light milling

operation.


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Maruifacturing Tec hnology U- Nov/Dec-2011 29Manufacturing Technology - II-Nov/Dcc-2011

13. (a) (ii) Describe the construction of the following milling cutter:(1) Plain Milling Cutters

Plain milling:

The plain milling, isthe operation of production of a plain, flat, horizontal

surface parallel to the axis of rotation of a p 1 am mi 11 ing cutt i ng. The

operation is called slab milling. To perform the operation, the work and the c-urtcr

is secured properly on the machine. The depth of cut is adjusted by rotating the

vertical feed screw of the Lable and the machine is started after selecting proper

speed and feed. The plain mailing operation is shown in figure.

F.nd Milling:

The end milling is the operation of producing

a flat surface which may be vertical

horizontal or at an angle kept reference ter

the table surface. The cutter usedisan end mill.

The end milling cutters are also used for

production of .slots. grooves or kcyways. A

vertical nulling machine is most suitable for end

milling operation figure shown an end milling

operations.

13. (b)(i}What is Radial drilling machine? Sketch and describe it.RADIAL DRILLING MACHINE'

This type of machine is mounted on floor and suitable tor drilling medium

to large and heavy workpieces. The most significant feature of bis machine is a

radial arm which can swing about a coiumn.

Plain milling Operation

D ,

^ UI Mill . ----------- 1

End Milling Ope


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Manufacturing Technology - If* Nov/Dec-2011

Ttic The main pans of the machine arc base, column, imlusJ ui m, drill bead,

spindle speed and feed mechanism.

Bas*

Radial drilling machine

1. Base11 is a large rcctangular casting. 3t supports the vertical column and table.

The- top surface of the base is accurately machined with T-$Iots to mount the

large size work pieces*.

2. ColumnColumn is a cylindrical casting mounted on Che base. It supports radial arm.

drill head and motor. The column face should be accurately machined to slide :he

radial arm up and down. An elevating screw is provided on the side of the

column to move t lie radial anil up and down The elevating screw is rotated by

the motor.

3. Radial armIt is a heavy casting mounted on the column. The drill head is mounted on l

he radial arm. Et has guide ways to move the drill head. The arni car. be swiveled

around the column. I: can be- moved up ufad dow n l>y rotating an eievato-r

screw.

Motor tar spindle

Jh**d

Column

1 ^ > I=

Moft* tare'*vabr*9 th* *nr

Racial ariTtetevattno wew


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Manufacturing Technology - II- Nov/Dec-WI ] 31

4. Drill headThe drill head is mounted on the radial arm. The drill head is equipped with

separate motor. The drill head is moved along the arm manually or with power

assistance. Dnil head has a spindle which carries drill bit.

5. Spindle head and feed mechanismThe spindle is driven through a gearbox. Feed can be manual or automati c.

Depth settings for production work with sut omaiic reversal is a standard feature.

Radial drilling machine may be classified with respect to the movements of

radial arm and tool head, '13ic vanous types of radial drillin g machi ncs arc:

(i) Plain type:The foIEowing adjustments arc available in this type.

Vertical movement ofthe radisal arm with respect to the column. >

Circular movement of Lhc radial arm about column.

Horizontal movement of the tool along the arm ways.-

(ii) Semi-universal type:In addit ion to the above three movements as in case of plain t ype, t he

fourth movement of the tool post can be swung about a horizontal axis

perpendicular to the arm This arrangement permits fen drilling a hole inclined at

any angle to the horizontal plane.

(Hi) Universal type-:

In addition 10 the above fourth movement as in case of* semi* uni versa!

lypc, the fifth movement of the ra dial a mi is rotated (tilted) or. horizontal axis.

13. (b) (ii) Sketch and explain the hydraulic drive of mhorizontal shaperalso enumerate any two advantages of hydraulic drive

lhc oil from the reservoir is pumped by gear pump It is driven by an electric

motor, l hc pump Supplies constant quantity of oil at a'


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MaivuEarturiuig fechobfogy - It- Novrt>ec-2011 33

The piston rod ds provided, in ihe lei) side. Il occupies certain volume. So

less volumrodc of oil c^iu be filled up in the left side. Bui tie pump, pumps theoi! at constant rate. Hence, when the oi I enters from, left side, it gives more

force. During t he return strok e the ram moves fast.J

Advantages of HydTJtniic Drive

1. Uniform cutting speed.*

2. Smooth and noiseless operation.y.Higher ratios of quick return can be arranged

4. Changing of cutting speed is easier.5. More safety due to the provision of relief valve.14. (a) (i) With help of sketches. describe any two methods of cylindricalgrinding

The c ylittdricas grinding machines, surfepc gracing machines ami internal

grinding machines conics under precision grinding machines category.

The principal of cylindrical gnodcr is shown in figure. In this the woikpiece

is held between the dead centres and rotated by a dog and driver on the faoc

plate. 1 here are four movements i n cyiindrical centre t\pe grinding.Grinding

X Wheel

Work Traverse

Cylindrical grinder


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Wareuficniriftg Technology - II- NoWDtc-ZQ] I

i) The work must revolve.ii) The wheel must revolve.iii) The work must pass the wheel.iv) The -wheel must pass- the worlc.

These grinding machines are used for grinding plain cylindrical parts,

although they can also be used for grinding cont oured cylinders, tapers,

shoulders etc.En cylindrical grinding two types of grinding operations are done

(i) Traverse grinding(ii) Plunge grinding

Traverse GrindingIn this work is reciprocated as the wheel feeds to produce cylinders longer

than the width of the wheel.

Plunge Grinding

In plunge grinding, the work rotates in fixed position as the wheel feeds

toproduce cylinders of a length equal to or shorter than the width ofthe wheel.

The gericial tangc of work speeds lorcytirdncal grinding is from 20 to 30mpm

(surface speed in meter per minute). Pin rye grindi ng requires vety low speed.

33

^/Feed

Plunge Grinder


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Manufacturing Technology - 11- Nov/Dec-2011 36

Plain centre type grinderReversing Table

Ptain Center type grinder

A plain centre

type grinding machine is shown m G gure. It

consists of the following - parts.

Base

Table

> Head Stock.

Tail Stock

Wheel Head

Cross Feed

On plain grinding machines, the operation may be stopped automaticallywhen the work piece has been finished to size. In one method automatic type

gauging attachment is used to measure the workpiece and stop the operation at

the proper time.

14. (a) (ii) Describe with neat sketches a gear hobbing machine and theway it generates the gear tooth.

Gear hobbing

Hobbing is a process of pet lerati :iy a "ear by tiMrans of a rotating cutter

called hob. The hub lias helical threads.. Grooves arc cut in

l~~Head Stock j

work piece-

Base AdjustableTripDogs for

/Lower Table

'. Movement of tbe Table for

Feeding \Table Reversing Lever


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Marutactxirmg.Techio!-ogy - II - Nov-'Dec-2(l 11 37

the threads parallel to the ax is. 'l his will provide llt-e cutting edges. Proper

rake and clearance angles are ground on these cutting edges. The rotating hobacts like a continuously moving rack as it cuts.

The gear blank is mounted on. a vertical arbor. The boh is mounted m a

rotating arbor. The hob axis is tilted through the hob lead angle a so that its teeth

are parallel to the axis of the gear blank.

Then a ~ (90* - a,)

Where a, - helix angle of the hob thread.

The hob axis is inclined at acwit h the horizontal as shown in the figure

Note : (hob lead angle90^ hob helix angle)

The hob is rotated at suitable cutting speed. It is fed across the blank face.The hob and blank are nt3de to rotate in correct relationship to each other i.e..

they rotate like a worn and worn gear in mesh. For one rotation of the hob, the

blank rotates by one tooth, (incase of single start hob)

Gear Hobbirrg

HOB AxisThough

a = (9(J-Beix Angle ofHob)

For cuti in g hehca 1 gears, die axis of the hob Is inclined to bori^ootal by a where.

-f*+ (90'- a,) (If t?*e helix of the hob and the helix of the gear to be cut arc different (i

e.) one is right handed and another is left handed.)


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Manufacturing T'-cclunolc-gy - fl- Nov/Dcc-2011 38

Where. 0 -Helix angle of the helical gear to be cut, a, - Helix aivgk of the bob.

Application:

Hobbtng is used for generating spur, helical and worm gears.Used in

automobiles, machine tools, vanous instrument 3, clocks and other

equipments.

Advanta gcs:

1. A single hob with the given module can be used for generating gear with anynumber of teeth of the same module.

2. The same hob can be used for spur and helical gears.3. Operations is continuous. So very fast rate of production4. Perfect tooth shape is obtmncd.5. Process is automatic and so less skilled operator is sufficient6. Worm gears are generated only by bobbing7 Multiple blanks can be cut at a time. Hence high rate of production.

Limitations: _

L Internal gears cannot be generated.

2. I lobbing cannot be usc-d for producing gear teeth veiy near to shoulders.


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Manufacturing Techno] ftgty - II- )I(WIDK-20I] 39

14. (b}


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MisniifmriujiTig TechnologyII- N*ov/Dcc-2Q] 1 40

SO microns. These

abrasive particles andg.as mixture arc allowed

to pass in the grinding

y.oru:through

and rotary action, of the grinding wheel.

In this case also, a constant gap of0.025mm is maintained between work and

wheel. In this process, 10% metal is removed by abrasive action of the grinding wheel

and 90% by abrasive jet action.

The grinding rate is affected by the following factors:

Cofnpnwaof

Air I rid

c

Production o-f abra*tve jet

the suitable 5?

aiso rotates. iso, uac

grinding of work surface

takes place by both ihc

abrasive action of abrasive

et

convergent ncv^Je So, the

brasive jet coining out will

e at high

cz


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Manufacturing TechnologyII- Mov/Doc-2011 41>

>Grinding wheel speed.

Abrasive jet velocity etc..

Applications

1. Ii is mainly used in grinditig hardened steel, ceanented carbides.2. It is used in resharpening and reconditioning of carbide tools.3. It is used in grinding thin-wall tu be w it hcxit leaving burr or distortionwhich are difficuIt to gri nd in any ot her process.


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Manufacturing TechnologyIf- INov/Dec-2011 42Adviatagti

1. No burrs arc produced.2. No heat is generated,3. Pressure exerted osi the work is less. -A.It .hasno wheel! wear.

5. Metal removal rate is. high.Disadvantages-

1. Cost is high.2. Power consumption is high.3. Skilled labour is required.4. Resharpening and rccond itioni ng of grinding wheels are needed.

(1) Honing:Honing i> a of machining with bonded abrasive grains, it serves to improve the shape,

size, accuracy and surface quality- as well as for outer surfaces

14. (b) (Ki) Explain the working principle and product application of the following process


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Manufacturing TechnologyII- Mov/Doc-2011 43>

(shafts)


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Manufacturing TechnologyIf- INov/Dec-2011 44On the honing machine, the workpiece (engine block, bush, etc..) travelsundcxthe boning

tooL on a table which moves endwise and crosswise. The

honing tool is suspended in the honing spindle with a ball-

aad-sooket-joint so that it can move' and

adjust to t he position of the hole. The rotary

motion of the spindle is impart ed to it by an

electric motor over a Piece steplessly variable

bcit or chain drive. The stroke motion is

generated hydraulioaily. and can . be

regulated in length, position and speed.

Because it must adjust precisely to the ax

ial position of the hole being honed, the

honing tool cannot be rigidly fixed to the spi

ndle. A ball-and-socket joint is therefore

interposed between the spindlpand the tool

{carda n ic suspension).

The Ironing tool has four or mote boning sticks mounted in iL The tool rotates snd

goes through an axial stroke motion at the same time. The stroke length is set so that the

toofi moves upward and downward beyond the workpiece by about W of its own length.

These motions combine to form a helical grinding track. Tliis not only improves the

surface quality, but also the cylindrical shape of the honed workpiece. This process does

not significantly affect the roundness of holes The honing sticks ore pressed and fed

against he generated surface by two cones inside the tool.

(2) Lapping:Lappmg isa process of chipping away material with loose abrasive grains. Hxtrcmely

high .accuracy of form and: dimensions, as well as very good surface quality. can be

obtained w ith this process.

HydraulicTransmission

Ho-ning machine


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Manufacturing Technology II- Nov/Dec-2011

Lapping Compound Lapping wheel Surface Lapping ProcessProcess :

The abrasive substance, consisting of silicon carbide, refined corundum, boron

carbide -or diamond, in grain sizes between 18 and )50pm, is mixed with a liquid foil,

kerosene, etc.,) and the mixture is known as lapping compound or lapping paste. Ibis

lapping compound cbips away material when it is introduced between the surfaces of the

lapping wheel and the workpiece and the two are moved against each other with theapplication of light pressure. The workpiece surface Is wo-m away more mpidly, because

the abrasive gra ins lodge in the softer and more porous- lapping wheel and act as cuti

ing wedges, against the workpiece. Another theory holds that the abrasive grains roll on

tlic w-orkpiccc surface and cause notches on iL The material, work hardens and tiny

particles chip off.

15. (aj (t) Kxplain. the toll-owing terms with retcrcnee to CNC machines1. Tool length compensation. 2. Cotter radios compensation.(I) Tool length compensation:

This machine centre compensation type allow the programmer to forget about eachtool's length as: lie program is wri ttcn. Instead of having to know the exact length of

each tooJ and tcdiousy calculating Z-axis posi tions based on the tool's 1 enjoh, the

pio.qramnscr simply instates tool length compensation on each tool's first Z-axis

approach movement to the work piece.

orkpiece Surface


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Maunjfsic tuting Technology -II- Nov/Dec* 201 1 42At the machine during setup, the operator -will input the tool length

compensation value for each tool in the corresponding offset.

If the tool length compensation is wisely used, the tool length compensation value

can be measured offline to minimize set u p time. With this method, the tool length

compensation value is simply the length of the tool.

(2> Cutter Radius Compensation:

Cutter radi us compensation allow the programmer to forget about the cutters,

radius as contours arc programmed. Cutter radius compensation, is used for only milling

cutters and only when mill iug on the periphery of.the cutter.

The usage of cutter radius compensation does vary' from one control to the other.

Once cutter radius compensation is properly instated. it the cutter will be kept on the left

side (or) right side of aJl surfaces to cancel compensation.Without cutter radius compensation, machining center programmers must program

the centerline path of all mill ing cutters. With cutter radius compensation the

programmer can program the coordinate of the work surface, which eliminates the need

for many

calculations..

As with tool length compensation, the opera tor casi use the cutter radius

compensation offset to help with sizing.

15 {a) (il) With a help of an example explain the difference between point to point and

continuous path type of numerically controlled machine tools.

Point to Point NC.system:

It is atsocal led positioning system. The objective ofLlicmachhte tool control is to

move the cutting tool tc a predefined location. The speed (or) path is not important in

this system.Continuous Path N'C system:

II is also called contouring NC system. Iliscapablcofperforming both point to point

and straight -cut operations.. More than one axis movement of the machine tool is

possible. The path of NC cu tier is continuously controlled to generate the desired

geometry of the work piece.

a) Point-To-Point (PTP) Motions Statement:There are only two basic commands arc available for PTP motions. They are:

GOTO and GODLTA

Tl >0 GOTO statement i nstructs the tool t o go to a pujticular point location

specified inihedcscripttvedaita. As mentioned abpvc, there are two ways available for


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Madu factoring TechnologyI t - Nov.'Dcc-ZOl1 43specifying live statements. For PTP motions, they can be

GOTOJP,GOTO/ -2.0, - 2.0. 0.0

In the first statements, the tool lias been instructed to move to a new

locatiou{destination point) P..

En the second statement, the tool has been instructed to move to anew location

(destinationpoint) whererheco-ordinaccsarc-2.0,

2.0. 0.0 i.e.. X - -2.0. y-2.Q- 2=0.0Tlie GODLTA command specifies 3n incremental to move the tool into the neiv

location. For cxampFc. consider the statement.

GODLTA/ 2.0. 2.0, 0.0

In the above-statement, the tool has been instructed to iftd-ve into the new locationfrom its current lecation by 2 own in *lie X-direcliicHi and 2nrm in the v-dinection.

while the z-direetion distance remains unchanged

The GODLTA command is used in drilling and oilier related operations. First ?ire

tool can be directed to move to a particulars hole location witJj'Oie'GOTt) statement

arid then the GOD-1. LA command would be used to drill the hole in that location.

From the above, the statement can be given as:

GOTO iP3 GODLTA/O. 1.5.-1.5

GODI.TA./0, 1.5. + 1.5

In a drilling operation, the GOTO statement is used to position tbc cutter to the

particulars location., where the bole has to be drilled and tbc GODLTA statement is thenused to plunge the cutter into the work piece to drill a hole. Another GOEH.TA

command is used to retract the tool, from the work piece. The sequence is repeated for

each hole.

b) Contouring Motion Statement:Contouring motions statements arc more complicated because the tools position

must be continuously control led throughout the move. To achieve this control, the tool

is directed to move along two intersecting surfaces. These surfaces have very specific

names in APT.

They are

1. Drive Surface2.. Part SurfaceIn addition to this, another surface must be defined to control the tool motion in con

touring.


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Manufacturing TechnologyII- NovXDec-2011 441. Drive Surface:

Drive surface is the surface that guides the side of the cutter. So, the tool slides along

this {drive-) surface.

2. Part Surface:Pan surface is the surface on which the bottom of the cutting tool travels or slides.

So, the tool end moves on the pan surface. It may or may not be the actual surface of the

work part.

So-, the pan programmer must define the part surface along with the drive surface in

order to maintain the continuous path control of the tool-


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Manufacturing Technology II Mov.Dcc-2011 462. Straight cut NG system.3. Contouring NC system.

1. Point to Point NC SystemIt is-also calledposition?, ng system.The objective of the machine tool control

isto move the cutting tool u> a predefined location.. The speed or path i s not important

in this system.

2. Straight cut method NC SystemThis system is capable of moving cutting tool parallel to one of r.he maj or axis ar a.

controilcd. rate fox- machining. lit is preferred for zn illing operations. Here, it is not

possible to combinc more than a single axis direction. Angular cuts are not possible.

3. Contouring NC SystemIt is a complex ar.d flexible method of tool .control. It i.s capable of performing;

both point so point and straight -cm: opera: ions. More than one axis, movement nfr-hc

machine-tool ispo'ss'iblp. The path of NC cuitcr is contiguously controlled Lo generate

the desired geometry of t he work piece. This sys tem is also called as conti nuous

pitth .VC si'S-iem.

Advantages of NC Machines

1: Greater accuracy.

2. Lesser prod uc-i oncost per piece duo to- reduction in lead lime anid also setuptime.

3. Improved product quality and provision of high order of rcjientabiliiy.


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Ball Buah uswd for Linear Mowemenrt In CHC ttacfWna Tools

i) Low co-efficient of frict ion; It is of the ocder of 0.004 as compared to 0.1 to 0.5which is typical of sliding friction power screws. Wear is therefore less and there is

very little need for frequent adjustment.

ii) In a ba II screw, the load between the t breads of the screw and the nut is nottransmitted by direct method contact but through intermediate rolling members

(spherical balls). The baL! rotate between the helical grooves of the screw and nut in

a manner a kin to their function in ball bearings. An essential features of almost all

ball screws is the provision of recirculation of halls.

iii)

By prcloading the assembly, clearance and consequent backlash can be eliminatedand the axial stiffness of the ball

Manufacturing Technology II- Nov-Dec-2011

Another type of linear motioa device is the use of a ball bush, where the balls arc

arranged in the trad: inside o f a busb, which can sJidc along a ground rod to provide the

I incar motion sim ilar to round slide ways used in convctuiosaJ machine tools, Figure

shows the typical ball bush used for linear movement in CfvC machine tools.

(2) Ball Screws

Ball screws arc employed in few mechanisms of CNC machine tools. When

compared with conventional trapezoidal and ACMF.. screws, the ball screws provides

many advantages.

Spiro Stsrft


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Manufacturing Technology II ApriL'May 2010 (E3134) 1Question Paper Code: E3134 B-.E/B.Tech. Degree Examinations,

April/May 2010 Fourth Semester Mechanical Engineering ME2252MANUFACTURING TECHNOLOGYII (Regulation 2008)

Time: Three hours Maximum: 100 marks

Answer ALL Questions PART - (10x2 = 20 Marks)1. How da you classify tool wear?2. Define Tool Life.3. Distinguish between Capstan in the form Turrcnt Lathe. A.State the different,methods erf Taper turning.

5. How do you classify milling cutters?6. Define Broaching.7. State the applications of honing and lapping finishing methods8. Compare gear forming with gear generation method.9. State the limitations of CMC machine toots.

JO. What is a Canned1cyde?

PART B( 5x10 = 80 Marks)11. (a) (i) Discuss the various types of chips produced during metal machining.

(6>

(ii) State the parameters that influence the life of tool and discuss. - (10)Or

(b)


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2 (E3134) AgrA'May 2010 ManutacUinnq Technology II14. (a) (i)Give the specification of grinding wheel. (6)

(ii) What is meant by dressing and truing of grinding wheel? (10)Or

(b) (i) List the advantages and limitations of gear shaping. (O)

(ii) Explain the principle of gear hobbing with neat sketches. (10)

15. (a) (i) Under what conditions of production the numerically controlled machinetools are employed? (6)

Explain the various elements of NC machine with closed loop control system.


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3 (E3134) Apnt May 2010 Manufacturing Technology II

4L State the different methods of Taper turning.


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Manufacturing Technology - II April/May 2010 (E3134) 4

9. State the limitationMofC7VC machine tools.(i) 71)0 price of CNC machine is very high.

fii) Maintenance is complicated. Special care should be token by specially trainedpeople.

(iii) Well trained professionals arc needed for writing part programs.

A Compare, gear forming with gear generation method.

Gear forming Gear generation

der this roll forming, extrusion, cold,

drawing methods axeincluded

Gear shaping. Gear hobbing areemployed

medal removal


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5 (E3134) Apni/Uay 2010 Mar+jt*cturIng Technology - Jl10. What is a Canned* cycle9

Canned cycle isused to define a series of machining sequences for drilling

(or) boring lor) tripping etc. The use of canned cycles reduces the programming*length required to perform certain operations.

PART B1L (a) (i) Discusi the various 4ypc$ of chips produced itaring met at machining.

Generally, there are following three types o-f chips

1. Continuous chip2 Discontinuous chip

3. Continuous chip with built up edgeContinuous chip

Continuous chips are normally produced when machining steel or ductile

metals at high cutting speeds. The continuous chip which is like nbbon flows as(shown in fig) along the rack face.

Continuous chip is possible because of the ductility of metal {steel at high

temperature generated due to cutting) that (lows along the shear plane instead of

rupture. Thus, on a continuous chip, we can not sec any notches It can be assumed that

each layer of metal flows along the slip plane till it isstopped by work hardening. Each

of the layer get welded to the previous ones because of the high temperature, thus

forming a continuous chip.

This, is most desirable form of chip, since the surface finish obtained is good


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6 {E3134) ApnkMay 2010 Manufacturing Technology - >1and tutting is smooth

Continuous chip with BUE (Built up edge)

When the friction between tool and chip is high vchilo machining ductile

materials, some particles of chip adhere to the tool rake face near the tool tip. \Vhf?n

such sizeable material piles up on the rake face, itacts as a cutting edge in place of the

actual cutting edge, as (shown in fig) This is termed as buik-up-odge


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Manufacturing Technology II AphiMw 2010 (E3134) 7


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Manufacturing Technology - II Aort:/May 2010 (E3134)17. (CL) (i i ) State theparameters that inf luence the fife of foot and discus*.

Factors influence (he tool lifeThe Life of the cutting tool is affected bythe following factors

(i) Cutting speedGO Feed and depth of cut

(iii) Tool geometry(iv) Tool material(v) Cutting fluid(vi) Work material(vii) Rigidity of work, tool and machine


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10 (E3134) Apn^/ay 2010 Mafhiactunng Technology - IIIt is numericallyequal to cutting speed that gives a tool life of one minute.

A typical cutting speed (V) . Tool life (T) relationship is shown in graphs.

Tool:lif6rTfrnjh)

In general, a para bob c decrease in tool life with increased cutting speed is

obtained. These plots indicates that as cutting speed increases with decrease in tool life.

(fl> Food and depth of cut

The life of the cutting tool is influenced by the amount of metal removed by the

tool per minute. On the fine feed, the area of chip passing over the tool face is greater

than that of a coarse feed for a given volume of metal removal. On the offset this

advantage in favour of the thick chip, the tool forces to produce thicker chips.

The effect of feed and depth of cut on tool life is givenby

257

Where.V" Cutting speed


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Manufacturing Technology - II April/May 2010 (E3134) 11T - Tool lifef fend in in m/m in t-

depth of cut in mmThe above equation is* valid/for low carbon steel by a cemented carbide tool.

Tool life is decreased with increase in feed and depth of cut.

(iii) Tool geometryLarge rake angle reduces tic tool cross section and hence the amount of heat

absorbed by the tool also reduced. This weakens the tool. Hence, correct rake angle must

be adopted for good tool life. The optimum rake angle for maximum, tool life lies

between - 5 to + 10 for turning operation. If the relief angle is more, less the friction of

the bool on th.e work But more relief angle decreases the tool life because of decreased

strength. The optimum relief angle is 12^ to 15\ Similarly, Hhigher value of Hide cutting

edge angles gives longer life to tool. The optimum side cutting edge lies between 30 to

25. Increase in nose radius improves the tool life? since the stress concentration is less

for greater nose radius.(iv) Tool material

A good tool material is one which removes maximum volume erf material at all

working speeds. Physical and Chemical properties of tool material will influence on tool

life.

(v) Cutting fluidHeat produced during metal cutting is carried away from the tool and work by

means of cutting fluid. It reduces friction at chip tool interface and increases tool Life

-Cutting fluid which, directly controls the amount of heat at the chip tool

interface and it is given by the formula.

T&1~C Where,

T- Tool life(J - Temperature of chip tool interface in

cC

n- An indeed which depends on shape and material of the cutting tool

(vi) Work piece materialTool life also depends on the microstructure of the work piece material. Tool

life will be more when machining soft metals than hard metals like cast iron and alloy

steel.

(WI) Rigidity of work, tool and machine

A strongly supported tool on a rigid, machine will have more life than tool

machining under vibrating machine.


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Manufacturing Technology - II April?^ay 2010 (3134) 13

... (i.

F^tutd to some convenient -scale and joinABto obtain their resultant. BisectABand draw a circle having the resultant force

as its diameter. Set off BE, making angle with forceFt%to cut. circle atE.Join

A. The magnitudes of iF^andFfare now known. Set off n line BG, at an angle

(90-a) with Fc(F, is vertical and BBJis horizontal SDBBris 90). Join GA. The

magnitude of forces N andFare thus known, as also the co-efficient of friction at

the chip - tool interface {FtAT). Angle BAG is the angle of friction between chip

and Tool.


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(E3i 34) ApnUMay 2010 Manufacturing Technology - II


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Manufacturing Technology 'I April/May 2010

(E3134)

(b) Analytical TreatmentRef fig (b)

F - GH+ HB =AI+HB

F - Fjcos a -t-F,- sin a

N=AG~DH DI

iV = F, cosa - jTf sin a

p Ffcos a +Ft sin aMfltX ..................... Illmmmamii.i

... (3)

Now N" Fr- cos a - Ffsin a

Dividing RS by cog aF Ff+ Ft- tan aH ~ F, - Fftan a

The resultant tool force.R(.equation)

Can be resolved into two components NandFnormal to and along the

rake surface respectively fig (b). Since fmust be the friction force due to the -

exixtencs; of the normal load JV, as per usual convention

Where JJis the average co-effident of friction between the chip and the

tool From eqns (1) (4) and (5)

. . .


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16 (E3134) ApriVMay 2010 Manufacturing Technology - II

NowFt-BDBD(Or/'.)

From AADD. Bed


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ManrJftduring Tecnriofofly - II Aprilrtday 2QT0 (E3134) 17

(i) BedThe bed is a long* box like casting fitted with rectangular way& upon

which are mounted the carriage and turretItalso supports the heads took. The bed

provides strength ind rigidity to other parts. It ensures proper alignment of partsalso.


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Manufacturing Tectnciogy - l Apr&/May 2010 (3131) 19

The* tools held in the turrent may be used to perform certain operations

on a workpiec, 'while* at the same time, other tools held in. the square tool post

mounted on the carriage do other operations.

The workpiece having been previously chucked correctly, with these

basic features of a turrent lathe, a number of tools can be set up on the machine

and then quickly be brought successively into working position so that a complete

part can be machined without the necessity for further adjustment or changing

tools or making measurements.

Operations such as roughing, knifing, tapping, boring, etc. can be

performed merely by rotating the hexagon turret and presenting to the workpiece

a different too] secured, in the turret, in order of sequence.

12* (a) (ii) Explain the working of Swiss type auto lathe with a neat sketch.

Single spindle chucking automatics are designed for efficient production

of parts which must be held in a chuck. All the tool movements, and speed and

feed changes arc controlled automatically. Parts are usually loaded and unloadedmanually. These machines are built with numerical controls or with electro

mechanical or hydraulic control system.

This type of automatic lathe is suitable for small but long and slender

parts like parts of wrist watches. There is a distinct difference between the

conventional automatic lathes and swiss type automatic lathes. In the latter the

work is fed against the tool. The head stock carrying the bar stock moves back

and forth for providing the feed movement in the longitudinal direction. Honce,

this: type of automatic lathe is also called a sliding head automatic lathe.

This type of machine has the following four mnjorparts Ci> The sliding

head stock, through which the bar stock is passed and gripped by a collet.

(ii) The tool bracket, supporting five tool slides, and guide hush for the barstock.


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f^a/vj'aciurinfl Tocftnoiogy - (I AprilMny 2010 {E3T34} 21

The main drive is from an electric motor at the bottom left hand of the

machine which drives a gear box housed in the cabinet base. From gear box the

drive is transmitted to the spindle by two roller chains which pass up through the

base of the bed. Thus the spindle speed can be varied from 60 to 200 rpm in

steps. The operation of these and the spindly clutch takes place from the back

shaft and tlius Ihe speeds could bo changed or reversed automatically also. On the

base of the machine is mounted a bed which carries the main dements of the

machine as listed below

1. Work spindle2 Back shaft (axial centred shaft)

3- Front shaft (cam shaft)

4. Turret and iUj slide5. Cross-slide (front and rear)In this type of machine, no special bar stop is required because the

headstock itself traverses. The parting off tool is left in the forw;ird position after

cutting through the bar in previous operation. The chuck opens and the head

slock moves back. The bar being preloaded move*- forward against the parting

off tool. When the head stock has reached its initial position, the chuck grips the

bar The parting off tool retracts and the work cycle commences.

This type of automatic lathe is the logical development of the capstan

lathe. These are actually automatic bar type turret lathes used for machining

external and internal surfaces on work pieces from the bar stock. The bar is

advanced to a stop automatically at the beginning of each cycle and then clamped

in that position up to six tools can be mounted on the tail stock turrent and other

on front and rear tool slides. Al! these tools are automatically fed at the correct

times during the cycle by cams. The various clutches are operated by trip dogs fastened to disc on the front

shaft.


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23 (pairv*) April/May 2010 Mgndacturrna Tochootogy - II

11L (h) (i) Whatis meant by "tool layout' of a turrent lathe?

Turret Lathe Tootling Layout

(i) Set up time(ii) Work handling time(iii) IVfadhine Controlling time(iv) Cutting time(v) Tool co?t(vi) Settop labor cost(via) Lithe operator labor cost

(viii) Number of parts to be manufactured Factors (i) to (iv) affect thearrangement of the tools in tho turret and tool holders. Factors (v) to (viii) relate to

the cost of producing parts on the turret lathe and thus determine whether turret

should be used for the snid purpose or not.The next step is to:


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Manufacturing Technology - II AonWlay 2010 fb3t34) 23

(iii) Decide length of travel ofthe tools and position of .stops. Select proper cutting speeds and feeds for each operation.

Cv) Set the work* tool holders and tools on the turret lathe.

Fig. Sample tool layout - 2

M2. (b) (ii) Name the various lathe accessaries How does a four

jaw chuck differ from a three jaw chuck?

Work holding devices are used eitiier for holding the workpiece or forsupporting the workpiece during- machining. Pew of the widely used work

holding devices are

1. Chucks 2. Centres 3. Faocplates 4. Reatw and 5-. MandrelsChuck: A chuck is a device, which, is us*d for bolding and rotating the job of

shorter length during machining. A chuck is usually equipped with three or four

jaws and accordingly it is classified as three - jaw chucks and four jaw chuck

respectively. These are shown in figure.


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IS-


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Manufacturing Tccbnotogv - II Apm'May 2010(C3134S

4. Straddle millingStraddle milling operation is theproduction of two vertical flat surfaces

on both sides of the job by using two side milling cutters which are separated bycollars.

Fig 4-Straddle milling

yprkpiece


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f^a?^faduring Tech^otofiy - 11 ApriEW.ay 2010 (3134) 29

Ffcg 7. End millings

8. T-slot milling

Killing of T-slot isproduced in two or three stages. In the first operation,

the end milling operation or a plain slot is made by using an end-milling cotter and

in second operation T-slot is made by using the T-Slot emitter to enlarge the slot and

to mill tbe bottom face of the slot as shown infig. &


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Fig. Gear cutting

It involves cutting ofdifferent types ofRear a.

13. (a) (ii) Explain different types of drilling machines tvith theirspecific features-

Drilling Machine

It is the simplest and accurate machine used in production shop. The vv'orik piteteis h


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32 (fc'3134! ApnUMay 2010 Tdanufact.>rJ>q Technotogy -

The table can also be Sevang to any desired position.m At- ibe top nf t_h** m'nmn th*>r


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34 (E3134)ApnVTv/ny 2010 Manulajcturing Technology - il

a*

Manufacturing Technology - II April/May 2010 (313^) _________________ 33

range? of spindle spe?d Fig 2 shows the line sketch of up-rightdrilling machine.

This machine usually has a gear driven mechanism for differentspindle speed and an automatic or power feed device.

Table can move vertically and radically Drill holes up to 50 mm.

Radial Drilling Machine

It the largest and most versatile used for drilling medium to large andheavy work pieces

Radial drilling machine belong to power feed type. Tine column andradial drilling machine supports the radial arm, drill head and motor.Fig. 3 shows the line sketch of radial drilling machine.

Or>jlHeaSB? -

mmer.* . J \7LfP-r>. !*'-.

~r?-Spind-e

Fig. 3 Radial Drilling Machine

> i" \


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The radial arm slides up and down on the column with the help of*elevating s-crew provided on the side of the column, which is driven by

a motor.

The drill head is mounted on the radial arm and moves an the guidewayii provided the radial arm can. also be swiveled around the column.

The drill head is equipped with a separate motor to drive the spindle,which carries the drill bit A drill head may. bo moved on the arm

manually'or by power.

Feed can be either manual or automatic with reversal mechanism./3. (b) (if Mucuss tJic various types of broaches.

A broach is a multiple - edged cutting tool that has *U4CCtfrvely higher cutting

edges along the length of the tool.* rr ------------------------: -------------- V :

:_ "Z ';

Dialer

xrJMilMilllM . . .1 4 ------------- -S?09lWQ*e*^ %-'

HeweROX f KiTVf I Filing Teelti

WU

HotfVcr

R^.eAr^.

Typical. CoostnMiar o Brooch

KVCK

TnoBflprt*

anuch $h&.'p*;ninrj

Revotwo.

' -"f : r*-t2^r

k

-nT


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Manutac:-jrir>n Technology II Aprilfl1ay 2010 (E3134) SS

Broaches are classified as follows;

1. According to the type of surface broached - internal broaches andexternal broaches.

2. According to the method of operation - push broach and pull broach.3.. According to the type of construction - solid broach inserted teeth

broach and progressive- cut broach

4. According to the operation performed on the workpiece. Surface broach, key way. round hole and spline etc.

Internal broaches are used for broaching internni surfaces. The broach will have

the same shape of the contour to be broached. Tor oa-ch shape and size a separate

broach is used External broaches are used for broaching outside surface. The

surface- may be flat, curved or any ocher contour

Push Broach is pushed through thr work during Culling operation. During

broaching: the broach comes under

compressive load. To avoid bending, the push broach is made short. So only a

few number of teeth are available in the broach. Holes axe broached using push

broaches only for finishing-. The push broach has got nicked teeth, in the front

portion. The rear portion has finishing teeth.

Pull Broach: A pull broach cuts the material while it is pulled through the work

piece. During pulling, the broach, comes under tensile load. So it will not bend

during machiniag.

Broach elements: Ordinary cut broaches for machining previously drilled or

bored holes consist of the following elements.

Pull End: This is designed to permit engagement of the broach with the broaching

machine through the user of a pull bead

Front pilot: This centres the broach in the hole before the broach begins to cat.

Roughing and Semi finish teeth: They remove most of the stock in the hole.


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36 (E3134) ApriVMay 2010 Manufacturing Technology - II

Finishing teeth: They are act swing: the hole and must have the shape required

at* thefinished hale.

Rear pilot and followed rest: They support the broach after the last tooth leaves

the bole.

Land: The top portion of a tooth is called the land and in most cases ground to

give a slight clearance.

Rack off or clearance angle: This corresponds to the relief angle of a single point

tool. This is 1.5 to 2: for both cast iron and steel. Finishing tooth have a smaller

angle ranging from 0 to 1.5

Broach Materi-al: Mast broaches axe made from 18-4-1 tungsten chromium -

vanadium steel, ground after hardening.

IS. fit) Discuss the comncon ivork holding devices used onshapers, blotters and planers.

The commonly used work bolding devices on these machine tools are

given below:

1. T-Bolts and HRmps

The table of machine tools such as shapers, $1 otters, planters, drilling

machines and milling machines are provided with T-skto. Most jobs can be held

on the machine table by means of T-bo3te, blocks and clamp plates. Fig


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MarmfacturirqTecftf>o!oay - H .AprilMay ?010 (E31S4)

(ety'Stbp pliw SCootto^

ASiy^ajSgf^ifg;.>&WS5, \'4-YM.

fa) Vlct;

2. Stop pins:inin-ftrr

Miiuniiiiii'ruii'irtnrgfftfrfrfB^v^~

~-""-,

rTr'rmrytF***

GlAtnpP#e

Sl.eftWCKK(FfcrjniFWW: W Mm.

. (d) St-w pini

CJairip |U.tlK

Wirt:


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MarmfacturirqTecftf>o!oay - H .AprilMay ?010 (E31S4)

tt*i1 (d, e)

S. Stop pins and Too-dogs

Fig- 1 fO. Hie arrangement is used for holding thin jobs particularly on

plancrs.4. Vises

Avise is a common work holding device, ft has two hardened jaws, one6xcd and the other movable with the help of a handle. The job is held between the

two jaws. The base of the vise carries slats or damping ears to fix the vise to thetable of the machine tool, with the jaws either parallel or


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38 (E3134) Aprt'Way 2010 Manufacturing Technology - II

suit Liiv difftl ent conUmrc- of jo be. For rouDd jobs,; Vecs may also bo fitted

instead of standard plain jaws.

The Swivel vise* is made in two parte. It consists of a round swivel base

over which, the vine body is mounUsd. The base is graduated into 360. The body

is damped to the base by zaeaas of clampsng bolts. The body can be adjusted atany angle relative to the base and sothe jaws can be sct at any angle. IT the* vise,

apart being swivelled in the horizontal plane, can also be tilted in the vertical

plane, it is called 'Universal. Vise.

SCO'

1 /scoEFGHI JKlMNOPQRSTUv^

If. (a) (VCirwe the spectficutiun uf gjhulUifs tchccL

; FriefcAhtr-r^Cbjcie

(^itcn Csrisie

Z*Ziiws '

V-Vfiirfei-fteir S-

fUte'

"ESte&c

so ! ?:: ?'.36m' 320


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m .Manufachjrjrva Technology - l April/May 20*0 (E3134)

ii. fa.) ftij WrAaf zj mrant by dressing and truing of grinding wheel?(b) I)muliiK uf lilt* Kri ud ii iK wl it rv l

With the passage of time, due to the use of thegrinding wheel, the wheel becomes glazec and

loadedzsexplained above and this lowers the

cutting capacity and efficiency of the grinding wheel.

Grinding wheels are dressed to restore their cutting capacity and cutting

properties.

Dressing a "grinding wheel is(1) To remove* metal or foreign matter}which has lodged in and loaded

(filled up) the pores of the' wheel. Fine grit wheels may load up quite quickly. :

(ii) To remove dull grains which did not break off. The dull grained (orglazed) wheel will burn the work and cause fine lmat crocks.

The Dressing tools: are most frequently single point

diamonds (shown in fig) which are mounted in metal held on the

grinding machine. These arc traversed across the face of a straight

wheel to dress it

Be- 6tfC?'4re leit* of;.^J-N^^dfcwp. vWf0wWw>;- .>>.fV4! 1/6' iotfPfor =a*?ry.


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(E3134) ApritMiy .2010 Manufacturing Technology II

With continu-oos use, a grinding wheel becomes dull, with the sharp

abrasive grains becoming round**!. This condition of dull grinding wheel withworn - out grains is termed as glazing. Further, some grinding chips get lodged in

to the space between the grit with the resulting condition known AS a lo-aded

wheel. Loading is generally caused during the grinding of soft and ductile

materials A loaded wheel cannot cut properly. Such a grinding wheel can be

cleaned and sharpened by means of a pToce*s called dressing.

A simple dressing is done by means of small steel disks wh->rh ar+

fr**o to rotate at the end of a stick. These disk -will remove o small portion of the

face of the wheel. Though this process is simple, since the dressing is done

manually it will not be able to produce a concentric surface.

A true surface of the gnnd wheel in terms of either the form or

concentricity can ho achieved with the help of a diamond dressing tool. A.diamond used for truing is set in a closely fitting hole at the end of a short steel

bar and is brazed. To do the truing operation, the grinding wheel is rotated and a

small depth of 0.(125 rum is given while moving the dressing tool across the face

of the grinding wheel in an automatic feed

T4. (b) (i) List Utr advantages anti limitation* of gear shaping.

In Gear shaping, when the machine is started, the cutter reciprocates vertically

and parallel to the axis of the gear blank. During generation process, both the

cutter and blank, are made to rotate slowly together about their axis.

The principle of cutting gear by the generating method has the advantage

that with a particular module of DP cutter it is possible to cut accurately gears

having identical module or DP. but different number of teeth-Applications

1. Gear shaping is used for generating both internal and external spur gears.


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Manirfacluring Tcchrx>k>sy - 1! Apr^May 2010 (E3134) 41

2. Helical gear can also be generated but up to Helix angle of 23* usinghelical cutter of opposite hand than the helix hand required on work

piece.Advantages of Gear shaping?

1., The gears produced by this method are wry high accuracy.2. Both internal and external gears can be cut by this process.3. Non-conventional types of gears can also be cut by this method.4. The production will be high.5/ By single cutter, number of sizes of gear?? can be produced

Limitations

The production with Gear shaper Is lower than bobbing. Worm, worm wheels cannot be generated on gear shaper.

14. (by {ii) Explain Ihe principle of gear FtoJfbung withnewtsketches.Gwar liobbisg

The most accurate way of cutting spur and helical gear is by the bobbing

process.

The cutter used in this process is known as Hob, which is as a rotarycutting tco-l with teeth arranged as a helical thread.

A (gear) hob (fig) car. be described as a cylinder with the surface,teeth thread has been cut. The thread has the shape of the involute

gear teeth- The hob is most frequently 75 to 350 mm in diameter.

Double and Triple thread hob? are also made. They cut faster but

less accurate

The hob revolves and cuts like milling cutter- It & teeth lie on aheliac like a worm. The teeth are form relieved behind tho cuttingedges.


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(gai34j Aprit'Slay 2010 Manufacturing Technology - H

A hot i used as a cutler on the g i h o b b i n g machJrvo

:Tfce. tVafar SSttfts at*

Orie End of Ihc f>earBlank ijrid Siowty;

:-cadsToward the i. !

:Oih6f ,Kod - I


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Manufacturing Technology II AfttiU'toay2010 (E313*) 43

The construction of a hobb ingmachine is on the line* of that indicatedat vertical or Horizontal, this referring to the direction

of the hob slide. In both the machine, the hob is. both rotating and

feeding:,

Fig

mft ii scan copy 2013

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