Surface Finishing Processes

About Surface Finishing Surface finishing may be defined as any

process that alters the surface of a material for aesthetic or functional purposes.

Objective :- Improve appearance and sales value of product.

The basis material (whose surface is being altered) can be a metal, a plastic, concrete, a ceramic; i.e. any material used for engineering or decorative purposes.

GrindingGrinding is the most common form of abrasive

machining.

It is a material cutting process which engages an abrasive tool whose cutting elements are grains of abrasive material known as grit.

These grits are characterized by sharp cutting points, high hot hardness, chemical stability and wear resistance. The grits are held together by a suitable bonding material to give shape of an abrasive tool.

Fig. illustrates the cutting action of abrasive grits of disc type grinding wheel.

Advantages:-Dimensional accuracy.

Good surface finish.

Good form and locational accuracy.

Applicable to both hardened and unhardened material.

Anodizing Anodizing is the process by which the natural

film on aluminum is greatly increased in thickness.

The oxide on aluminum is naturally corrosion resistant, very hard, abrasion resistant, an insulator and very tenacious. In its natural form the oxide film on aluminum is less than 0.50 microns thick.

Because the naturally occurring film is very thin and attached to a soft ductile metal, it is easily damaged.

Fig. Schematic of Anodizing Process

Advantages:-Protects satellites from the harsh environment

of space.

Provides attractive, minimum-maintenance, highly durable exteriors, roofs, curtain walls, ceilings, floors, escalators, lobbies and staircases in skyscrapers.

Considered environmentally safe, producing few, if any, harmful effects on land, air, or water.

LappingLapping is regarded as the oldest method of

obtaining a fine finish.

Lapping is basically an abrasive process in which loose abrasives function as cutting points finding momentary support from the laps.

Material removal in lapping usually ranges from .003 to .03 mm but many reach 0.08 to 0.1 mm in certain cases.

Characteristics of lapping process: Use of loose abrasive between lap

and the work piece.

Usually lap and work piece are not positively driven but are guided in contact with each other.

Relative motion between the lap and the work should change continuously so that path of the abrasive grains of the lap is not repeated on the work piece.

Fig. Scheme of lapping process

Advantages:- The Fastest & most accurate method of

achieving flatness with the ultimate degree of surface finish.

Stress free process without thermal distortion.

Rapid turnaround of work! No fixing or clamping required facilitating a rapid set up.

HoningHoning is a finishing process, in which a tool

called hone carries out a combined rotary and reciprocating motion while the work piece does not perform any working motion.

The honing process is carried out by mechanically rubbing the honing stone (cutting tool) against the work piece surface (normally internal) along the controlled path.

Fig. (i) Honing tool

Fig. (ii) Schematic of Honing Process

The abrasive action of the honing tool removes material from the work piece's inside diameter.

The tool rotates and expands while the work piece reciprocates (stroking) back and forth.

Advantages:-Good bore geometry such as roundness,

cylindricity, straightness and surface finish.

Lower friction across the interior surface.

Has a positive impact on productivity, owing to smoother, faster inner surfaces.

Ensures consistency of dimensions.

PREFERENCES Google Imageshttp://machiningbymorley.wi

kispaces.comhttp://www.coatfab.comhttp://www.ignou.ac.inhttp://www.wikipedia.com

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