Ductile Machining of Brittle Materials by Ultra-precision Raster Milling

Abstract

Ultra-precision raster milling is widely regarded as a very promising technique for achieving deterministic fabrication of functional or freeform surfaces on a wide range of engineering materials. In raster milling process, the diamond tool rotates on the spindle with a large swing radius, so the diamond tool intermittently contacts and departs the workpiece surface with a large idle duration for each rotational cycle. The unique machining strategy of raster milling leads to totally different brittle-to-ductile transition phenomenon from those of turning and ball end milling when machining hard-and-brittle materials. This section experimentally studied the brittle-to-ductile transition phenomenon, cutting forces, and surface topography in ultra-precision raster milling of single-crystal silicon. The experimental results show that A much deeper ductile-cut region can be obtained by raster milling compared with the ordinary diamond sculpting method, indicating the superiority of raster milling in fabricating structures on brittle materials without fractures. Compared with diamond turning, raster milling achieves much uniform finished surface quality on single-crystal silicon, due to its unchanged cutting direction. Ultra-precision raster milling has the potential to be applied to fabricate different functional surfaces with ultra-high form accuracy on brittle materials.