Study on ductile-mode mirror grinding of SiC ceramic freeform surface using an elliptical torus-shaped diamond wheel

Abstract

An elliptical torus-shaped diamond wheel is proposed to perform a freeform axial-feed grinding of SiC ceramics. In elliptical form-truing, a new mutual-wear between rotary grinding wheel and fixed dresser is developed to produce an elliptical wheel-profile along elliptical interpolation paths. The objective is to understand how the ductile-mode mirror grinding of hard and brittle material is related to the diamond wheel-profile along with microscopic grain protrusion parameters and macroscopic grinding variables. First, the models of grain cutting depth and surface roughness were constructed by considering grinding variables, grain protrusion parameters, machined curve surface and wheel curve surface; then, the transfer from brittle-mode grinding to ductile-mode grinding was experimentally investigated in connection with elliptical torus eccentricity and grinding variables; finally, the surface quality and the form accuracy of ground freeform surface were observed. It is shown that the elliptical wheel-profile produces larger wheel working area and more valid diamond grains than the arc wheel-profile even in axial-feed grinding of steep freeform surface. It contributes to decreasing the grain cutting depth to the critical cutting depth without nanometer-scale depth of cut, leading to efficient ductile-mode grinding. The experimental results also show that the number of brittle micro-crack and surface roughness easily decrease to ductile-mode mirror grinding state with increasing elliptical torus eccentricity. It is confirmed that accurate and mirror freeform grinding of hard and brittle material may be realized by using an elliptical wheel-profile along with valid grain protrusion and suitable grinding variables.