Thermal analysis and machinability for laser-assisted machining of fused silica

Machining of fused silica to obtain high precision dimension and surface property has been an industry wide problem. In this study, laser-assisted machining (LAM) of fused silica has been introduced with three-dimensional thermal models been built to perform detailed analysis. The accuracy of the model is validated by measuring the temperature of workpiece and poly crystalline diamond (PCD) tool. The appropriate combination of machining parameters has been analyzed, as well as the temperature distribution at material removal layer, cutting zone of workpiece and PCD tool. A uniform temperature distribution is obtained at workpiece surface, with a very small temperature gradient of 20 K at the radial depth range of 100 µm after preheating. Although the temperature at cutting zone of workpiece is 1490 K, it is much lower at nose of tool with a value of 510 K, which is contrary with common belief. In addition, the experiments under higher temperature in LAM and lower temperature in conventional machining (CM) are carried out to study the machinability with respect to subsurface damage, chip morphology and tool wear. The results indicate that the machinability in LAM of fused silica is greatly improved, attributed to the maintenance of excellent performance of the PCD tool, and along with the changes in hardness, strength and viscoplasticity of fused silica.