Arc Envelope Grinding of Sapphire Steep Aspheric Surface with SiC-Reinforced Resin-Bonded Diamond Wheel

In order to improve the grinding wheel wear during the sapphire steep aspheric surface grinding process, a SiC-reinforced resin-bonded hemispherical diamond wheel was used and the arc envelope grinding performance was investigated. Firstly, the mapping relationship between the contours of the grinding wheel and the aspheric surface was established based on the grinding conditions. The wear of the hemispherical diamond wheel was modelled, and the result indicates that the maximum wear occurred at the edge of the hemisphere, decreases along the generatrix and increases near the center. Then, the form-trued diamond wheel was used for grinding the sapphire steep aspheric surface. The concave and convex surface form error obtained at the central part of phi 50 mm are 2.5 mu m and 1.3 mu m, respectively. The surface roughness R-a is 230-450 nm, which is affected by the material removal rate and the sapphire crystal anisotropy. The SiC-reinforced resin-bonded diamond wheel possesses favorable self-sharpening ability and sufficient diamond grain retention capacity for sapphire grinding. The wear distribution shows that the most severe wear parts of the grinding wheel are at the edge and the center of the grinding zone, which is consistent with the model-predicted results.