Investigation of surface and subsurface damage in diamond grinding of optical glass using hybrid copper-resin-bonded diamond wheel

Abstract

Hybrid metal-resin-bonded diamond wheel has more advantages for ultraprecision machining of optical glass than the usually used resin- or metal-bonded diamond grinding wheel. In this article, the grinding performance is investigated using the copper-resin-bonded 5-μm-grain-sized diamond wheel via contour grinding assisted with electrolytic in-process dressing. The surface roughness and figure accuracy were measured with an atomic force microscope (AFM) and Taylor–Hobson profilometer, respectively. The subsurface damage was first evaluated by a new method presented in this article, which was realized via observing the subsurface damage by AFM along the magnetorheological finishing polished groove surface. Then a common method was used for measuring the subsurface-damage depth and observing subsurface cracks, which can also prove the feasibility in evaluating the subsurface damage of the new method. Furthermore, the energy-spectrum analysis was used to evaluate the surface and subsurface by an x-ray energy spectrometer. The experimental results show that the ground workpiece (optical glass BK7) with surface roughness of 6–30 nm and subsurface-damage depth of less than 2.2 μm was generated with the hybrid-bonded diamond grinding wheel. The grinding process introduces the carbide element as an impurity into the surface and subsurface. The results indicate that a copper-resin-bonded diamond wheel can generate surface and subsurface integrities of optical glass with high quality.