Ultra-high-speed grinding of Si3N4 ceramics

Fine ceramics, especially Si4N4 ceramics, are promising as structural materials. In using Si4N4 ceramics as structural parts, it is important to develop more economical machining of the ceramics with low damage for finished surface. This paper presents feasibility of the Ultra-High-Speed (wheel speed: 60-180 m/s) and low damage grinding process for Si4N4 ceramics with the newly developed metal-bonded wheel. Grindability was evaluated by grinding force, specific grinding energy and material strength after processing in the Ultra-High-Speed cylindrical grinding of Si4N4 ceramics by using the metal-bonded diamond wheel with homogeneously controlled distribution of grain cutting edges. Main results are summarized as follows: High efficiency grinding of a stock removal rate of Z'=50 mm(3)/mm.s was achieved at a wheel speed higher than 60 m/s, and 10-20% strength degradation was observed by grinding at a stock removal rate of Z'=50 mm(3)/mm.s vis-a-vis to mateial strength before processing. These results indicate the experimental achivement of high efficiency and low damage processing. The point of this study is the small wheel depth of cut necessary for low damage grinding was achieved by increasing the wheel speed at an even high material removal rate. The metal-bonded wheel with homogeneously controlled distribution of grain cutting edges was used to decrease damage for finished surface.