Investigation of subsurface damages and surface roughness in grinding process of Zerodur® glass-ceramic

Subsurface damages and surface roughness are the two significant parameters which determine the efficiency of optical components. In this study, a cup diamond wheel is used in grinding process of the specimens made of Zerodur® glass-ceramic, to investigate the influences of grinding parameters on the SSD and SR. The grinding parameters used in this study are depth of cut, cutting speed and feed rate; and effects of these parameters are studied. The experimental results are compared with the modified model of Lambropoulos, proposed by Li, and a good accordance is observed between them. Two measuring techniques were used to study the SSD. Cross-sectional polishing method and angle polishing method; the first one, suitable for studying the material removal mechanism and the other one convenient for examining the depth of subsurface damages and distribution of micro-cracks in the ground surface, respectively. A novel technique is introduced to measure the cracks length in which the sum of all cracks in a specific area of a SEM micrograph is calculated by image processing method and regarded as a factor to study the cracks length. Also, a statistical model is developed in order to predict the surface roughness and a good agreement is observed between the experimental results and the predicted values.