ELID grinding characteristics of glass-ceramic materials

Zerodur glass-ceramic materials have been widely used in optical, opto-electronic and precision engineering industries; their efficient ultraprecision machining, with extremely low surface roughness and high form accuracy, is in great demand in those fields. The authors have been conducting studies on realizing high-quality surface and form accuracy of zerodur glass-ceramic materials efficiently by use of electrolytic in-process dressing (ELID) grinding process. This paper proposes a new grinding mode in which top surface and sides of zerodur block were ground by cylindrical surface and side surface of grinding wheel. Grinding experiments were carried out using #1200, #2000 and #4000 diamond cast-iron bond wheels, and grinding characteristics such as grinding performance, ground surface roughness, surface topographies and perpendicularity between ground surfaces were investigated. Experiments on grinding using #4000 wheel successfully produced smooth top surface and side surfaces that were about 10 nmRa in surface roughness, 1.5 μm/□400×400 mm2 in flatness and 90°±6″ in perpendicularity. AFM observation of the ground surface also showed that material removal in the ductile mode occurs for fine abrasive wheels. The results showed that grinding was stable without severe clogging for wheels by choosing suitable ELID parameters and grinding conditions.