surface finishing processes

7/17/2019 Surface Finishing Processes

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Abrasive Machining and

Finishing Operations

Er. Narinder Singh

Scientist, CSIO



Abrasive Machining

• A process which removes small amounts of

material in the form of small tiny chips through the

contact of sa!!, hard, sharp, noneta!!ic partic!es.



Abrasive Machining

Processes to finish and smooth surfaces

Very low MRR

Very high surface finish

Dimension accuracy and control

Workpiece materials may be too hard

Workpiece materials may be too brittle



Finishing Operations

•Coated abrasives•Wire brushing•Honing

•Superfinishing•Lapping•Polishing•Buffing

•Electropolishing•Magnetic-field-assisted polishing



"oning• "oning is used to remove small amounts of

ateria! to produce an exacting size and surfacefinish.

• Most coon app!ication is to produce precisesurface finish in engine cylinder walls and

hydraulic cylinder fabrication

• Rotation and axial oscillation is used to producethe desired surface throughout the entire !ength ofthe ho!e.

• "oning is done with cutting fluids and honingstones, specia! grinding stones with #$%&$$ gritwith the addition of additives to odif' the cutting



Honing

• In honing, a siu!taneous rotating and reciprocating otion

between an abrasive stone and the wor(piece causes the reova!

of a sa!! aount of ateria!.

•)he resu!ting wor(piece surface is one of high precision and

unifor finish.



Honing

Figure: Schematic illustration of a honing tool used to improve the

surface finish of bored or ground holes.

• Stone: Al !" or SiC bonded abrasives



ylindrical Honing

FIGURE : Schematic of honing head showing the manner in which the stones

are held. The rotary and oscillatory motions combine to produce a

crosshatched lay pattern. Typical values for Vc and Ps are given below.



IE *&* C!ass Notes b' Figen Eren

+$

Honing

• Honing is an operation that is used primarily to improve the

surface finish of holes produced by processes such as boring,drilling, and internal grinding.



Advantages of Honing

• Rapid and economical removal of stoc!

• Minimum of heat and distortion

• "eneration of round and straight surfaces

• #asy correction of taper$ Out of roundness• %evelopment of any desirable surface finish

• Accurate control of &ize

• MRR upto '.( mm



Superfinishing

• Superfinishing is a variation of honing that is t'pica!!'used on f!at surfaces. )he process is

- er' light$ controlled pressure, +$ to /$ psi

- Rapid 0over /$$ c'c!es1 in2, short stro!es)!ess than +1/ in.

- &tro!e paths controlled so that a sing!e grit never traversesthe sae path twice

- Copious aounts of low)viscosity lubricant)coolant f!oodedover the wor( surface



&uperfinishing *s Honing

• 3ower operating speeds

• On!' for obtaining for 4ua!it'

surface finish

• Man' otions to get fina!

finish

• Most!' used for e5terna!

surfaces



Figure: Schematic illustrations of the superfinishing process for a

cylindrical part. (a) Cylindrical mircohoning, (b) Centerless microhoning.

&uperfinishing



&uperfinishing

FIGURE : In superfinishing and honing, a film of lubricant is established between the

work and the abrasive stone as the work becomes smoother.



+apping

• Lapping is an operation used for finishing flat, cylindrical, or curved

surfaces.

• Lapping is the process of mixing loose abrasives with vehicle such as oil

and letting it remove material from the work piece at very controlled rate.

• To reduce roughness, waviness & other irregularities on the surface

• Used on both heat treated and non heat treated surfaces

• Accuracy is main consideration with limited appearance of finished surface



+apping

• 3apping is the process where the abrasive media ischarged 0ebedded2 into a softer edia ca!!ed !ap.

• +ap material range fro various t'pes of c!oth, or softeta! such as copper.

• )he embedded particles do the cutting not the !ap.

• )he abrasive is carried away by the lapping oil, orcoo!ant, and needs fre4uent rep!aceent.

• 3apping reoves ateria! very slowly and is t'pica!!'used to remove machining and grinding mar!s,producing a po!ished surface.



+apping ,rocess• Abrasives - Natura! as we!! as Artificia! !i(e A!*O6, SiC,

Eer', 7owered garnet, 8iaond

• *ehicle - )o carr' or retain the abrasive during process.

Coon!' used vehic!e are eg, 9ater So!ub!e, Minera!,

:erosene and O!ive Oi!, ;rease, A!coho! etc• -ype of lapping Operations

% E4ua!ising 3apping

% For 3apping

• +apping Methods

% "and 3apping

% Machine 3apping



3apping

Figure : (a) Schematic illustration of the lapping process. (b) Production lapping on flat

surfaces. (c) Production lapping on cylindrical surfaces.

•Lap: cast iron# copper# leather# or cloth

$e%bedded in the lap&



)ertiar' Manufacturing 7rocesses

3apping< Superfinishing



Polishing Pads

Lapping Machine



IEM%MAE OS= *6

'esources

Strasborough CMP M(c'etaining 'ing

Wafer

Carrier

PolishingPad

LapMaster Lapping M(c



+apping ,rocess

• Refining &urface finish

• "eometrical accuracy of flat $ cylindrical and

spherical surfaces

•ot to remove metal but to finish to some size

• ,rovide a close fit between mating parts



+apping ,rocess

• /ncreases wor! life by removing surface roughness

and irregularities

• &uperfine surface finish

•"reater uniformity and Optical flatness

• Accuracy limits upto '.''0 mm

• Removes errors in gears which produce noise and

wear



Ref: Fig. .!", #alpa$%ian. &anufacturing Processes for 'ngineering &aterials nd 'd, ddison*+esley --.

Flame Cutting

Snagging (Coarse Grinding)

Sawing

Planing, Shaping

Drilling

Chemical Machining

Milling

Broaching

Reaming

Electron!eam Machining

"aser Machining

Electrochemical Machining

#urning, Boring

Barrel Finishing

Electrochemical Grinding

Roller Burnishing

Grinding

$oning

Electropolishing

Polishing

"apping

Super%nishing

Electricaldischarge Machining

Process microinches

micrometers &'

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+*

&'

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&

*+

+

'*-

'*.

+

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-

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/0erage /pplication"ess Fre1uent /pplication

Surface roughness b) %achining



Surface >oughness a!ues



Surface >oughnessSurface roughness is generally described ith of methods

Ra* rithmetic &ean /alue* the average of the absolute values

of the deviations from the center line of the surface

Rq (formerly R&S)* Root &ean S0uared*

Rq = a2 + b2 + c2 + d 2 + ...

n

Ra1 *a* + *b* + *c* + *d* + , n$ &



>oughness =nits

• + Microeter ? +µ ? + icron ? +$%& eters

• + Microinch ? +µin? +$%& inches

• +µin ? $.$*@ µ

• +µ ? /$ µin

• "uan hair /$ µ

Both generally given in micrometers (microns) or

microinches



Machined Surface



Abrasive low !achining

Figure: Abrasive low !achining to deburr a turbine impeller. The arrows indicate movement of

abrasive media. "ote the special fi#ture, which is usually different for each part design.

surface finishing processes

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