superfinishing process

PREPARED BY:-DHIREN P PATEL5TH SEM MECH.ENGG.(120013119002)

Super finishing processes

A.D.I.TMechanical department

WHY SUPER FINISHING REQUIRED

Parts Worn Out Fast Due To Defects Of Grinding Operation. The Defects Are Chatter Marks, Helical Type Scratches, Surface Cracks, Smear Metal Etc. Are Responsible For Wearing Out The Parts. In Certain Circumstances High Surface Quality Is Required. Hence For Removing Grinding Defects, To Obtain Desired Surface Finish And To Improve The Geometrical Shape Finishing Processes Are Used. It Includes Honing, Lapping, And Super Finishing.

FINISHING METHODS

• With material removal – generative methods

-fine machining, honing, super finishing, lapping

• Without material removal – forming method

-glazing, blasting, tumbling, polishing

TYPES OF SUPER FINISHING PROCESS

• Honing

• Lapping

- Hand Lapping

- Machine Lapping

• Super Finishing

HONING

• Hole made by boring is obtained to required dimension and finishing by honing. In this process abrasive stone is used. The dimension to an accuracy of 0.005 mm can be obtained by honing process

• Honing is wet cutting process. 6 to 8 honing sticks are held together and metal is removed by rotating or reciprocating the holder.

• Honing tool is rotated at a speed of 0.5 - 2.5 m/s and reciprocates at a speed of 0.2 – 0.5 m/s.

• Objectives are achieved by honing1. Metal is removed

2. Roundness & straightness is obtained

3. Accurate dimension is obtained

4. Required surface finish is obtained.

•Application :

-Honing Of Automobile Cylinder

-Honing Is Also Used For Repair Work

LAPPING

• This process mainly done on the meting surfaces. Abrasive compound or solid bonded abrasive is used in it. More accuracy is obtained as heat & pressure are less in lapping. Lapping compound is made by mixing diamond, silicon carbide, aluminum oxide in oil or water. There are many types of lapping process.

HAND LAPPING

• In this method lapping compound is spread on cast iron plate and work piece is moved manually on it on a path like English figure - 8

Machine lapping

• In this method a rotating table is used in place of the plate. Again the work piece to be lapped is given rotary by a cage and rotated on the surface of the table. Rotating lap is used above & below the work piece to produce parallel surfaces.

- Machine lapping process is carried out for gauge blocks, piston pin, ball bearings and engine valves.

Application of lapping:-

SUPER FINISHING

• This process is one type of honing , in which as compared to the honing less pressure, high speed, huge amount of lubricant – coolant of low viscosity and more contact area between work & abrasive face is kept. Less heat is produced during super finishing and it is generally done on external surfaces.

POLISHING

• Abbrasive material is bond

to a tool (disc, belt) or it is a media (paste) freely between tool (textile disc, belt) and

part

• NO improve in shape or accuracy!!

• Just improves the surface quality

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