Ultra-precision grinding of BK7 optical glass using coarse-grained electroplated diamond wheel

A novel conditioning technique is developed to precisely and effectively condition the 151 μm grain-sized nickel electroplated monolayer coarse-grained diamond grinding wheel in aiming to realize ductile grinding of brittle materials. During the conditioning process, a copper bonded diamond grinding wheel (91 μm grain size) dressed by ELID (electrolytic in-process dressing) is applied as a conditioner, a force transducer was used to monitor the conditioning force, and a coaxial optical distance measurement system are used to in-situ monitor the modified wheel surface status. Ultimately the coarse-grained diamond wheel is conditioned to achieve an ideal state in terms of less than 2 μm run-out error, top-flattened diamond grains and constant wheel envelop profile. Then the well-conditioned 151 μm wheel is applied to conduct taper grinding and contour grinding tests, the ground surface and sub-surface integrity are measured by WLI (white light interferometer), AFM (atomic force microscope) and SEM (scanning electrical microscope) respectively. The experimental results indicate that the well-conditioned 151 μm grain-sized diamond wheel is able to realize ductile grinding of BK7 with nano-scale surface roughness, as well as the almost damage free sub-surface integrity. The results also show the promising prospect of the conditioning technique and coarse-grained diamond wheels to be applied in machining the hard-machine-materials and the other brittle materials such as ceramic and silicon carbide, etc.