Subsurface damage mechanisms in diamond grinding of BK7 on tetraform 'C'

This research investigates the diamond grinding mechanism of optical glass and the resulted surface and sub-surface by a novel ultra-stiff machine tool, Tetraform 'C'. During the grinding process, an acoustic emission (AE) sensor and a piezoelectric dynamometer were used to monitor the grinding process and the grinding force components correlating to different characteristics of the material removal transition. SEM and AFM microscopes were used to evaluate the ground workpiece surface topography and sub-surface integrity. The nano-indentation technique was applied to evaluating the ground glass surface properties in terms of nano-hardness and elastic modulus. The Experimental results show that for BK7, nanometric quality surfaces (Ra < 5 nm) with minimal subsurface damage depth (<1μm) could be achieved with a relatively large diamond grit size (6-12μm) metal bonded grinding wheel at a high material removal rate, due to the ultra high closed loop stiffness of Tetraform 'C'.