Arc-Enhanced Plasma Machining Technology for High Efficiency Machining of Silicon Carbide

Atmosphere plasma etching methods have been demonstrated efficient in the etching of fused silica or ULE. However, because of the high chemical stability of silicon carbide (SiC), the conventional plasma etching methods seem incapable of obtaining a high material removal rate (MRR). We have found that MRR will be significantly improved while the electric spark appears between the plasma and the SiC surface. As a result, a new plasma source is designed to generate stable arc at the surface. Due to the generation of arc, the MRR of 0.35 mm3/min is obtained, about 10 times as high as the conventional method. In this paper, the removal characteristics and the thermal effect of this method are presented. MRR and the surface temperature are investigated in dependence on plasma parameters: RF power, travel speed of plasma source, SF6 gas flow and O2 gas flow. Due to the negligible thermal effect, the surface figuring can be achieved using the conventional dwell time method. The shape error of a flat SiC surface is corrected, verifying the figuring capability and the effectiveness of this method.