Cutting model considering damage layer thickness for ultra-precision turning of quartz glass

Quartz glasses have been extensively used for many fields. However, quartz glass is a typical brittle material so that a certain thickness of damage layer appears after conventional mechanical machining. Single point diamond turning (SPDT) is usually employed in the non-ferrous metal machining to achieve nanoscale surface. Recently, there has been an increasing interest in research on the machining of brittle materials SPDT. This paper aims to study the process of turning quartz glass with diamond tools with certain edge radius (several micrometers), in which tool wear is practically taken into consideration. The cutting model is established to estimate the damaged layer thickness on the machined surface through volume of extrusion area. The undeformed chips shape considering the strain rate in this model is obtained by numerical simulation method, which is used to solve the above volume. Then, the experiments of turning quartz glass with different cutting depth, feed rate, and cutting speed are carried out. The experimental results show that the lateral crack depth calculated by the model has the same variation pattern as the surface roughness Sk value, and show good consistence when the feed rate is ranging 1–4 μm/r with the cutting depth which is 2 μm. In addition, the calculation results of the model show that the depth of median crack less than the depth of lateral crack can be achieved with cutting depth ranging 0.2–2 μm while feed rate is 1 μm/r. The research is useful to optimize the turning parameters to reduce the damage layer in quartz glass.