Micromechanics of diamond composite tools during grinding of glass

Precision optical components are now manufactured by CNC (computer numerically controlled) grinding technology using diamond composite tools. Tooling performance, and in particular consistency of performance, is an important issue in this automation. A key measure of performance is the power/forces required for material removal, often summarized in terms of the specific grinding energy or ‘Prestonʹs coefficient’. In this study measurements of grinding energy were used, along with optical profilometry measurements of tool surface features, to quantitatively characterize the performance and development of a bronze-bond composite diamond tool during grinding of three optical glasses with distinctly different grinding behavior. Evolution of grinding performance is strongly related to both the process conditions and the glass type. These effects can be understood in terms of changes in the relative rates of bond and abrasive wear and the consequent evolution of the tool surface. In particular in certain cases the evolution of tool surfaces can be adjusted toward a state of dynamic equilibrium (‘selfsharpening’) by adjusting process conditions.