Developing a trend prediction model of subsurface damage for fixed-abrasive grinding of optics by cup wheels

Fixed-abrasive grinding by cup wheels plays an important role in the production of precision optics. During cup wheel grinding, we strive for a large removal rate while maintaining fine integrity on the surface and subsurface layers (academically recognized as surface roughness and subsurface damage, respectively). This study develops a theoretical model used to predict the trend of subsurface damage of optics (with respect to various grinding parameters) in fixed-abrasive grinding by cup wheels. It is derived from the maximum undeformed chip thickness model, and it successfully correlates the pivotal parameters of cup wheel grinding with the subsurface damage depth. The efficiency of this model is then demonstrated by a set of experiments performed on a cup wheel grinding machine. In these experiments, the characteristics of subsurface damage are inspected by a wedge-polishing plus microscopic inspection method, revealing that the subsurface damage induced in cup wheel grinding is composed of craterlike morphologies and slender cracks, with depth ranging from ∼6.2 to ∼13.2 μm under the specified grinding parameters. With the help of the proposed model, an optimized grinding strategy is suggested for realizing fine subsurface integrity as well as high removal rate, which can alleviate the workload of subsequent lapping and polishing.