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Manufacturing of Valves

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The inlet and outlet valves are basciallymade of two steels namely,

i) Austeniteii) Martensite

The material is chosen depending on the

customer requirements.

Valve Material Store

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Pre Machining processes

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This is a special process, done when twoparts is to be combined during manufacture.

There are two types in frictional weldingnamely

1. Head to pin

2. Pin to pin

Frictional welding

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In pin to pin process a martensite bar iswelded by means of frictional heat to aaustentie bar.

In head to pin process, head and stem of thevalve are made seperately and attached

together

Frictional welding

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Principle: This principle is that when arotating bar comes in contact with astationary bar friction occurs and heatproduced due to friction melts and rejoins

the metals.

Frictional welding

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First austenite bar is held in a collet andplaced in a spindle.

Then along its horizontal axis, themartensitic bar is held along a v block.

The spindle starts rotating as the machine isturned on and the v block capable of movingalong a horizontal axis is moved and madeto come in contact with the rotating bar thusproducing friction in it.

Due to the heat of friction the the,martensitic metal melts and gets welded

with the other bar, forming a bulged portionin the region welded.

Frictional welding

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S.No Friction weldparameters

1. Temperature Depends on the materials

welded

2. Spindle rotation Speed 1050 rpm

3. Upset force 1.1kg/cm^2

4. Frictional force 0.41 kg/cm^2

Frictional welding

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This operation is done to remove the buldgeportion after frictional welding.

It using turning operation it is removed.

Deflash

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Here the welded bar is kept in a collet whiichis placed in a spindle.

A cutting tool placed in a tool post is movedhorizontally over the rotating bar and thebuldge portion is removed.

Deflash

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This process is used to form a bulb portion,which then converted to head portion byforging.

Upsetting

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The setup consists of two anvils.The upperone is fixed while the lower one is capable ofmoving in a vertical axis.

To the fixed anvil current is being continouslypassed.

Now when the lower anvil holding the bar israised up and brought in contact with theupper one, due to high current the metal gethot and expands.At the same time due toupset pressure the bulb shape is formed.

And when the anvil is brought back down at

specific time due to return pressure the bulbis completed.

Upsetting

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The parameters to be checked while theprocess are

i) anvil gap : 2-5mm bar dia

ii) Upset Pressure

iii) Return pressure

iv) Electric current

Parameters ii,iii,iv depends upon customerrequirements

There are two types of anvils used in this

process, namely, special and regular

Upsetting

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The parameters needed to checked afterupsetting are

Upsetting

S.No Parameter Inspection

1 Cracks in bulb Visual inspection

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Principle: Forging is a bulk deformationprocess which works in the principle thatwhen requisite force is applied to manipulatethe metal in such a way that the required

final shape is obtained.

Forging

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This process is basically done to get thehead of the valve.

Generally for forging operation carbide die isused.

Forging

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In this operation, the hot upsetted bar isplaced in the bottom die vertically with thebulb facing upward.

By air pressure operation the upper die ismade to strike the bulb, thus forming thehead shape.

Forging

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The following parameter should be checkedduring the process

Stop pieces are used to increase the lengthrequired for increasing the height.

Forging

S.No Parameter Limit value

1 Stop pieces Various lengthrequired

2 Guiding die bush +.1-.13mm higherthan bar dia

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The following parameters should be checkedafter the forging process

Usually in forging operations steel die is usedas it can be used to make 500 jobs.

Forging

S.No Parameter Verification method

1. Overall length Length measuringgauge

2. Stem runout

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Treatment

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Generally for pure Martensitic valvesHardening and Tempering is done.

For bimetallic valves solutionising andageing is done.

The reason is since Austentite is the hardestamong the steels it is remains at samehardness level irrespective of anyconditions.So solutionizing is done so thatthe hardness of martensitic material rises toa high grade and gets maintained at thehardness of austenite.

Heat Treatment

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Principle:Continous expose to hightemperature for a short duration(1 hour) andsudden quenching in oil/water/air expandsthe material and increases the hardness of

the bar.

This process is done for martensiticmaterials to improve the hardness andstrength of the material.

Hardening

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The following parameters are followed duringhardening process depending on thematerial

Hardening

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Material HardenedHardness

Temperature(degrees)

Soaking time(min)

Valve Stem

EN 18D 45 830-860 10-20 60

EN24 45 830-860 10-20 60

EN52/X45

CrSi 93

48 1000-102010-20 60

SUH3 46 1000-102010-20 60

SUH11 48 900-930 10-20 60

SAE4110/ 45 830-860 10-20 60

Hardening

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In this process the valve is kept inside achamber maintained at a temperaturementioned for the material of the valve.

The valve is exposed to this temperature for

about 1 hour so that the material expandsand its hardness increases.

After the specific time the valve is oilquenched to cool it.

Hardening

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Generally a bauxite furnace is used forcooling in which hot oil is placed withseparate tubes for air and water.

After the process the material is checked for

its hardness using a hardness tester.

Hardening

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This process is done for to produce highquality hardened valves and also to reducethe brittleness of the valves to a certainextent.

Tempering

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In this process the valves are placed inside acontainer where they are exposed to a muchlower temperature compared tohardening(600-700deg.) for a quite long

time(3 hours).The difference between hardening and

tempering is in hardening it is exposed tohigh temperature for short time duration

but in temperature it is exposed to lowtemperature for long time duration.

Tempering

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After it has been removed from the furnace itis cooled by means of air for some10minutes time.

After this process the hardness is againtested by means of hardness tester.

Tempering

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This process is used for removal of scalespresent over the valves.

Principle: By continous contact of the valvesover sand removes the scales over thevalves.

Short Blasting

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Here first the valves are loaded on the shortblast furnace.

Then the doors of the furnace is closed andlocked.

Now the elevator motor is switched on firstfollowed by the impeller motor.

Now the impeller rotates and the continousriddling of the valves over the sand occurs.

Now after the specific time, when theimpeller stops(after switching off),the valvesare unloaded.

Short Blasting

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The places of occurance of failure are

Short Blasting

S.No Failure Rectification

1 Black spots onradius

Quantity per lotcan be reducedor more time forshort blastingcan be carriedon.

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This process is primarily used to straightenthe stem axis wrt to the axis of the head.

Straightening

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The parameters to be checked duringprocess are

Straightening

S.No Parameter Specification

1. Roller pressure20-30 kg/cm^2

2. Straightening

time

1-1.5 sec

3. Angle Roller

F49595F40745

F39599

45 deg angle roller

to be used

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The valve is first placed in the machine.When the machine is switched on the and

the cycle is begun, the valve is acted by 7rollers,2 * 2 on its either sides and 2 on its to

surface and an angle roller.These rollers straighten the stem axis.The pressure of the top roller is about 30

kg/cm^2 and the return pressure is about 15kg/cm^2

Straightening

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After the straightening process thestraightness of the stem,profile radius andhead thickness are checked.

Straightening

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Special Processes

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All the special processes mentioned beloware done only when the customer specifiesthem.

Special process

d i

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Here a recess is formed in the valve seat ofhead region for coating stellite in the region

Also in this process the head diameter is alsoreduced according to the required value.

The principle of this operation is nothing but

turning.

Turn Head DiameterRecess

d i

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In this process the valve stem in placedinside a collet and then into a spindlecapable of roation.Now the machine isswitched on and the spindle rotates

The head region is now influenced by twocutting tools individually.

First the diameter of head is reduced torequired limit by the first cutter then the

recess is formed in the seat region by thesecond cutter.

In both the cases turning operation is carriedout.

Coolent is used to removed the heat


T H d Di

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The following parameters should be checkedduring the process


S.No

Parameter Specification

1. Feed SPMManual

THD

Recess

2. Coolant Soluble cuttingoil and water inratio 1:40

1.0/1.2mm/s

.

T H d Di t

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The parameters to be checked after theprocess are


S.No Parameter Verification

1. Head Diameter Snap gauge

2. Head runout Fixture FX-1with .01 dial

3. Recess profile Profile Projector

T H d Di t

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The possibilities of failure in this process ischittering which can be removed by using awire cut tool.


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In this process the seat is hardened bydeposition of stellite in the recess formed inthe seat portion by TIG welding.

The basic method for this deposition processis TIG welding process.

Stellite is deposition on the seat to harden itso that it may not wear out during working.

Seat Hardening

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In this process the job is loaded in the baseplate and cycle is switched on.

Now the base plate rotates and electrode towhich current is flowing and which is jus

above the seat recess gets heated and meltsover the recess due to which stellite getscoated over the recess.

The shielding gas protects the weld

pool,electrode from oxidation.Flux gets settled down over the weld as slag.In this process a grade 6 electrode is used.

Seat Hardening

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The parameters to be checked while weldingare

Seat Hardening

S.No Parameter Smallvalves

BigValves

1. Weld current(A) 90-120 140-150

2. Upslope time(s) 1-4 1-4

3. Downslopetime(A)

1-4 1-4

4. Job Rotation Machinespecific

Machinespecific

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The parameters to be checked after weldingare

Seat Hardening


equipment1. Deposit form

and filling upProfile projector

2. Bonding Die penetrant test

3. Porosity, Blowholes

Visual

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The various failure possibilities in thisprocess are

Seat Hardening

S.No Parameter Rectification

1. Inclustion Set the req.currentCheck quality of

rodRegrindelectrode andreset it.

2. Valve melting Change base

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This process is used for pressing the weldedportion with the seat.

The basic principle is the heating and

forging.

Coining

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In this process the welded area is heated bymeans of oxyacetylene flame.Also when anyprint is to made on the bottom of head thenthat region is also heated.

Then in red hot condition the valve is placedwith its heads flat portion facing the top dieand its seat resting on the bottom die.

The top die has the imprint to be printed

over the flat end of head.When the top die strikes the flat face of head

the imprint falls over the valve and at thesame time the weld flattens over the alongwith the seat.

Coining

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The process parameters to be taken careduring the process are

Coining


1. Oxy pressure 2-4 kg/cm^2

2. Acetylenepressure

.5 kg/cm^2

3. Coining temp 950-1000 deg

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Parameters to be checked after process are

Coining


1. Overall length Fixture FX-6 withlength bar

2 Head thicknessProfile projector

with oil drawings3. Radius profile4. Material on

seat

5. Head diameter Micrometer with

Ray tech gun .

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Places where failure can occur are

Coining

S.No Parameter Solution

1. Filling up reardeposit

junction bed

Check Valve heattemperature andcheck blow setting

2. Stem runout Check stopper

settingCheck die bushbore

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This operation is done in the tappet end ofthe valve to reduce the length of the valve.

The basic principle is grinding operation.

Wet End

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In this process the valve is kept over the V-block and the machine is started.

Now the Tappet end of valve is faced overthe rotating grinding wheel thus resulting in

reduction in length.Th contact time is .5 sec to 1 sec.This process is done before and after cavity

drilling and tipping process respectively.

Wet End

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The process parameters to be noted duringthe process are

Wet End


1. Depth of cut 1-2 mm

2. Feed 7-10mm/s

3. Pneumatic pressure 4-5 kg/cm^2

4 Grinding wheel speed1600-1800rpm

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The parameters to be checked for failureafter the process are

Wet End

S.No Parameter Verification Remedy

1. OverallLength

Fixture FX-6with .01 mmgauge

Checkfacestopperbutton

andgrindingwheelbearing

2. Tappet end Fixture FX-4 V-Block

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This process is used to form a cavity in thetappet end of the valve for filling stelliteduring tipping.

This process is nothing but drilling where acavity is drilled over the tappets flat end.

Form Cavity

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The valve is held in the collet and placed inthe machine with the tappet end facing thecutter.

Now the machine is switched on and the

rotating driller is moved a horizontal axis anddrills a cavity on the tappet end.

Hydraulic force is used to move the drill.

Form Cavity

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The parameters to be checked during theprocess are

Form Cavity


1. Drill speed

Austenite21-4N,SUH38 750-850rpm

MartensiteSUH3,SUH11,SNB16

2. Air pressure 5-6 kg/cm^2

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Parameters to be checked for failure afterthe operation are

Form Cavity

S.No Parameter Verificatio

n

Remedy

1. Cavity Depth FX-6fixturewith .01dial

Checkdepthsetting

2. Cavity form Profileprojector

Reworkbad valves

3. Cavity finish Visual Check drill

bit for

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This operation is nothing but depositingstellite in the cavity drilled in the tappet endto increase the hardness of the tappet endso that it maynot wear when the rocker arm

strikes it during the operation.

This operation takes place by the weldingprinciple.

Tipping

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In this process a grade 1 stellite electrode ismelted using an oxyacetylene flame over thecavity drilled portion in the tappet end.

Stellite fills the cavity thus hardening thetappet end.

Temperature during welding is around 3500deg at the electrode.

Tipping

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Parameters to be checked during the processis

Tipping


1. Oxygen Pressure2-5Ksc

2. AcetylenePressure

.5-.7 Ksc

3. Flame Type X-3x/ x-4x

4. Height of deposit1- 1.5 mm

5 Deposit of

material

Stellite grade I

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Parameters to be checked after process are

Possibilities of failure are

Tipping


1. Height of Deposit Height gauge

2. Porosity/density X-ray testing

S.No Parameter Remedy

1. Valve melting Check for flamesettingReduce wall

thickness due to

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Machining Processes

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This process is done to reduce the stemdiameter.Amount of diameter reduced canbe upto 300microns in this process.

This operation taking place is centrelessgrinding.

Rough Centreless Grinding

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In this process the stem region of the valveis subjected between two rollers namely thegrinding wheel and control wheel.

The distance between the two wheels must

be equal to the diameter of stem aftergrinding.

Due to the action of the two rollers and theblade over the stem the diameter of the

stem reduces to the required value set.


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The parameters to be checked beforegrinding operations are

Hydraulic pressure must be maintainted

properly else if pressure is*high it leads to oil leakage

*low it leads to bed movement



1. Coolant Biocool

2. Hydraulic pressure 20bar

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The parameters to be checked after grindingare



1. Stem Diameter Fx11 fixturewith .01 dial

2 Stem runout

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Head Turn Diameter/Finish

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The Valve is inserted in the collet and held ina chuck.

Now a the inserts are placed in a tool postcapable of moving in both the axis.

When the machine is switched on the firstinsert reduces the thickness by facingoperation and the second cutter chamfersthe head region by chamfering operation.

Head Turn Diameter/FinishFace


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Parameters to be checked before the processare

Collet clamping pressure- hydraulic pressure

Gripping of all other arms-Air pressure



1. Collet clampingpressure

30-33kg/cm^2

2. Air Pressure 5-6kg/cm^2

3. Coolant Cooledge


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Parameters to be checked after the processare



1. Head diameter Go and No GoGauge

2. Head dia runout FX1 with .01mm

dial gauge3. Head thickness Pot Gauge FX7

fixture with .01dail

4. Chatter marks in Visual

Profile Turning(ACE Cube

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This operation is done in the profile of valveto give clearance in seat and stem neck sothat the valve fits properly in the enginecylinder.

Here turning operation in done with the CNCover the stem neck and profile.

Profile Turning(ACE CubeCNC)


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In this process when the machine is switchedon the with the valve in the collet thetriangular insert carries over turningoperation from the stem neck till over the

profile.Finue oil is used as coolant in this process..Ace cube CNC consists of a tool post which

can carry upto 8 inserts.



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1. Radius profileProfile projector2. Seat runout

3. Head

Thickness

Pot gauge fixture

FX7 with .01 mmdial

4. Undercutdiameter

Snap gauge


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The various failure possibilities are



1. Head Dia variation Change

insert2. Head dia runout Check collet

runout

3. Seat runout

Turn reduced stem,groove and end

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In this process overall length of tappet end isreduced,tappet end is chamfered,and grooveis formed.

The principle behind these are turning andchamfering with the respective inserts in theCNC machine.

Turn reduced stem,groove and endfacing


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First the valve is held in collet and it isplaced in the spindle.When the machine isswitched on the spindle starts rotating and inthe tappet end a 45 deg insert reduces

precisely and produces chamfer bychamfering operation.

Then using a triangular insert specifiedlength of the tappet end is turned to form

small threads of less thickness and dia.Then at the specified space in the tappet

region the groove is formed using a grooveinsert.

The groove is used for holding the valve in



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The parameters to be checked while theprocess are


S.N

o

Material SystemPressur

e

ColletClampin

gPressure

Pneumatic

Pressure

DwellTime

Spindle rpm

Tipindexing

Freq.

1 X45

CRS19325-30kg/cm^2

15-20Kg/cm^2

3-5kg/cm^2

.1-.5Sec

2400Const

1200

2 X45CRS193

1600


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Parameters to be verified after the processare



1 Overall length Fixture F6 with .01mm dial

2. Tappet endradius/camfer

Profile projector

3 Groovediameter

Shape gauge

4 Groove runout Fixture FX1 with .01mm dial gauge

5 Groove finish Visual

T t d i di

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This operation is done to finish the flatsurface of the tappet end.

This process is similar to wet end grinding

expect to that this process is done in CNCautomatically.

Tappet end grinding

T t d i di

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In this operation the valve is placed in a V-groove and its tappet end is faced againstthe rotating wheel.

The operation time is less than a second.

Only when this operation is done, the heat isuniformly conducted throughout the tappetin induction harden end operation else it willlead to irregularities.

Tappet end runout is be checked after theprocess using a pot gauge.

Tappet end grinding

I d ti H d E d

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This process is done to harden the tappetend of the valve so that it doesnt wear outduring the operation.

The principle behind the process is heat isproduced by passing electric current througha coil and when the tappet end is exposed tothe space between the coil it gets heated

and gets hardened.

Induction Harden End

Ind ction Harden End

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In this process the Tappet end of the valve isattached to a collet which is attached to aspindle driven by a motor and which canmove in a horizontal axis.

The tappet end is suspended between acopper coil through which electric current ispassed.

When the machine is switched on the spindle

rotates and electric current is passedthrough the coil.Due to the process ofinduction heat is generated in the coil andthe tappet end thus hardening the tappet

end.



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The following process should be checkedduring the process



1 Motor Speed 60 rpm const

2 Cooling oil Meta quench39 or equal


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The following parameters to be checked afterthe process



1 Hardness on tappetend

Rockwellhardness tester

2 Barrel length V block with

micrometerattachment

3 Depth of hardness By acid etching


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The possibility of failure is



1 Variation of hardnessand depth

Check inputvoltagevariationAlso

Check tappetend and coildistance andair gap.

Induction harden seat

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This process is used to harden the seat sothat it doesnt wear out when it operatesduring engine operation.

The principle of this process is similar to thatof the induction harden end.



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In this process the Tappet end of the valve isattached to a collet,vertically, which isattached to a spindle driven by a motor andwhich can move in a vertical axis.

The tappet end is suspended between acopper coil through which electric current ispassed.

When the machine is switched on the spindle

rotates and electric current is passedthrough the coil.Due to the process ofinduction heat is generated in the coil andthe tappet end thus hardening the tappet

end.



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The following process should be checkedduring the process



1 Motor Speed 60 rpm const

2 Cooling oil Meta quench39 or equal


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The following parameters to be checked afterthe process


S.N

o

Parameter Verification

1 Hardness on seat Rockwellhardness tester

2 Hardness survey Micro hardness

tester3 Hardness depth By acid etching


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The failure possibilities during the processare



1 Variation of hardnessand depth

Check inputvoltagevariationAlso

Check tappetend and coildistance andair gap.

Centreless grinding I

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This operation is done for reduction in stemdiameter.

Removal limit is around 100 microns

Rough grinding operation and CF I cannot bedone as a single operation because it leadsto runouts and overheating.



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The following parameters should be checkedduring the process



1 Max materialremoval

.1 to .25 mm

2 Grinding wheel

speed

1400 rpm

3 Control wheelspeed

380 rpm

4 Control wheel head .5 1 deg


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In this process the stem region of the valveis subjected between two rollers namely thegrinding wheel and control wheel.

The distance between the two wheels must

be equal to the diameter of stem aftergrinding.

Due to the action of the two rollers and theblade over the stem the diameter of the

stem reduces to the required value set.


Centreless grinding I for

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seat


1 Stem Diameter Fixture FX! With .001/.002 dail

2 Stem runout Fixtture FX5 with .001/.002mm dial

3 Blending radius Profile projector

4 Parallel grindinglength

Length gauge

Centreless grinding I for

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Chances of failure in the process are

seat


1 Stem runoutexceeding uppertolerance limit

Checksetting ofblade length

2. Chatter mark onstem Controlwheel speed.

Nitriding and

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The objective of nitriding of this process to toimprove wear,friction,fatigue and corrosiveproperties and to improve the valveappearance.

Vibro polishing is done for smooth surfacefinish of valves after nitriding and also forremoval of salts.

Vibropolishing

Nitriding

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The valves are arranged in the jig plate andloaded in the degreasing tank using hoist.

After decreasing the valves are rinsed inwater and transferred to the preheating

furnace using hoist and is preheated.Within two minutes after preheating it is then

transferred to the nitriding bath after which itis quenched in oxidising bath.

It is then removed and allowed to cool for 2minutes and quenched in water to cleanthem.

Nitriding

Vibro polishing

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In this process the nitrided valves are placedover a large container containing abrasivesand capable of vibrating.When the machineis switched on the container vibrates to and

fro and constant collision of valves with theabrasives causes the polishing effect in thevalves.

The process is done for almost half an hour.

After vibro polishing,it is dipped in sodiumnitrite solution and followed by rustpreventive oil.

Vibro polishing

Grind Seat

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This process is used for grinding the valveseat so that it may easily sit in the cylinderwithout wear.

The operation done is grinding.

Grind Seat

Grind Seat

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In this process the valve from chute movesto the grinder when it is acted by a grindingwheel and a cutter which removes 5 microndia in the valve seat making it comfortable

to sit during operation in the engine cylinder.

Grind Seat

Grind Seat

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The parameters to be checked after theoperation are

Grind Seat


1 Seat angle Profile projector

2 Seat height Pot gauge

3 Seat runout Fixture FX3 with

0.001mm gauge

4 Seat finish Surface finishtester

5 Datum to end Pot gauge FX9

Grind Seat

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The possibilites of failure are

Grind Seat


1 Seat runout Check collet

runout and wear

2 Seat height Check overalllength variation

3 Seat anglevariation

Check belttightening boltsare fully tight.

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Finish Centreless Grinding

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The remaining all parameters are same asthat of CF1 expect to that of here in thisprocess material is removed for smoothfinish.

Finish Centreless Grinding

Nitriding

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After finish centreless grinding is donenitriding process is done again forsmoothness and valve appearance.

Nitriding

Final Inspection

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Here every aspect of the gauge is inspectedand verified whether they are withintolerance range.

Only when they are in tolerance limits they

are selected else they are reworked.

Final Inspection

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Thank you

dine sh

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