Comparison of the subsurface damage induced when precision grinding ULE® and Zerodur® surfaces

A precise and rapid grinding process, with low levels of surface waviness and subsurface damage, can improve the total cycle time for producing large ULE® and Zerodur® optics. In this paper, the subsurface damage level of ULE® and Zerodur® were investigated and compared. Resin bonded diamond cup wheels were employed. The grinding response was characterized by measuring: surface roughness, surface profile and subsurface damage. The amount of defects beneath ULE® and Zerodur® surfaces ground using the selected grinding mode were compared. The observed subsurface damage can be separated in two distinct depth zones, the first 'process' related and the second being 'machine dynamics' related.