(6) Finished surface roughness of electrolytic grinding

[Fig.1] shows a mechanism that determines finished surface roughness. The figure shows a relationship between the grinding wheel and the ground surface. The area "b" is subject to electrolytic grinding.

However, the area "b" is not the only area filled with electrolyte. The electrolyte supplied by the nozzle will fill the "c" area while traveling to the "b" area, as well as overflowing to the "a" area. The electrical current will in all the areas and etching action will occur in all three areas.

The "a" and "c" areas not touched by the abrasives are affected only by electrolytic etching. The "a" area will be removed as the process advances so the surface roughness is not affected.

The "b" area is affected by etching as well as the mechanical grinding. Since this area will remain as "finished" and the surface roughness is somewhat affected.

In the "c" area, the effects of etching on the surface will gradually lessens as the wheel's contact point pulls away from the surface. But since the area is the final finish that remains after the process, the effects on roughness is the greatest.

When all three areas are compare for roughness, it shows that area "a" is the roughest, and the area "b" is the least rough. The area "c" is rougher than "b" and this is the area of the final finish roughness. It is thought that the area "c" becomes rougher than "b" because of some stray current.

If the etching occurring at area "c" can be prevented, best finish can be obtained as the final finish. It is not possible to completely eliminate the etching at "c", but some measures can be applied to reduce to a minimum. In practice, the applied voltage is increased and table feed rate is increased to reduce the "c" time duration to a minimum.