Lapping Compounds Abrade Surfaces To Fine Finishes

2007-03-08 10:33:40

( Games-Toys )



Lapping is a low velocity abrasive machining process, where you use loose rolling abrasives in a liquid or paste vehicle. Lapping machines apply pre-determined pressures and relative motions between the lapping surface and the surface to be lapped. The process results in an accurate surface finish.

Lapping compounds consist of the abrasives-plus-vehicle mixtures. If you are in the semiconductor industry, you use a flat lapping machine for lapping silicon wafers before the wafers move on for dicing in dicing machines. With the use of flat lapping machines and appropriate lapping compounds, the wafers acquire a perfectly flat surface.

You generally use lapping compounds between two surfaces. For general industrial lapping compounds, you can choose among silicon carbide, aluminum oxide, and garnet. Some lapping compounds contain small diamond particles in a grease base.

A woodworker would work only with silicon carbide lapping compounds. Metalworkers prefer to use aluminum oxide lapping compounds for mild steel, stainless steel and bronze. Glass and plastics call for garnet. You can use diamond lapping compounds of medium grit for general applications to get very fine finish and close tolerances.

Lapping compounds contain different levels of abrasiveness, referring usually to the size of the grits used as abrasive. Thus, lapping compounds have labels bearing the type of abrasive used plus a number.

Lapping machines remove material from workpiece proportionally to the following influences: lapping speed, wheel pressure, lapping compounds used (grit type and size, type of lapping liquid, and proportion of grit per unit of liquid). Lapping machines often have specific lapping compounds assigned to them in the workplace.

The volume of stock removed increases with the speed of the wheel. Since the penetration depth of the grit does not change, lapping speed cannot affect the surface finish. However, the penetration depth changes with increased pressure, which does affect the finish.


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