Ultra-precision grinding of hot-pressed zinc sulfide

To overcome the shortcomings of traditional lapping and polishing methods in machining large size aspherical hot-pressed zinc sulfide lenses, a machining experiment on hot-pressed zinc sulfide materials was performed by diamond wheel grinding method.. The single-point diamond scratching and orthogonal grinding experiments were carried out to research the ductile regime removal mechanism and subsurface damage during machining hot-pressed zinc sulfide and to obtain optimal machining parameters. The results of micro-indentation experiment show that hot-pressed zinc sulfide materials under a load are easy to produce radial cracks and micro cracks, the toughness value is 2.643842 MPa/m^1/2 and the critical cutting depth is 1.808 μ m. Based on the results of single-point diamond scratching, it verifies that hot-pressed zinc sulfide is removed in ductile regime at a smaller cutting depth although much kinds of subsurface damage will appear during machining process. The results of orthogonal grinding experiments demonstrate that the depth of grinding is a main influencing factor on surface roughness values, which decreases with decreasing depth of grinding, and the best value is 7.6 nm. The feed rate of the working table influences the surface figure precision PV values mostly, it offers the surface accuracy (PV) between 0.185 μ m and 0.395 μ m. These results show that the roughness of hot-pressed zinc sulfide surface by grinding has been up to nano level.