Investigation on the effect of laser energy distribution in in-situ laser-assisted diamond cutting single-crystal silicon

Abstract

Diamond cutting is a widely utilised ultra-precision machining technique. In-situ laser assistance helps in heating and softening hard and brittle materials, thereby enhancing the machinability. However, conventional Gaussian beams suffer from significant thermal gradients, high thermal stress, and poor energy utilisation. In this study, we present the novel integration of the beam shaping techniques with the in-situ laser-assisted diamond cutting process to analyse the impact of laser energy distribution on the machining performance. The equipment with top-hat beam assistance was developed based on optical simulation. The effect of the laser energy distribution was analysed via thermodynamic simulations and experiments. Furthermore, the temperature-stress distribution, surface forming mechanism, cutting force, and residual stress were analysed. The results indicate that a top-hat beam can achieve a more uniform temperature field, thereby effectively reducing the peak temperature and the heat-affected zone depth. It further reduces the generation of thermal stress and inhibits the thermal damage. The laser energy efficiency is improved by softening the material at the edge of the irradiation zone. When compared with Gaussian beam assistance, the top-hat beam increases the critical cutting depth for the brittle-ductile transition from 274 nm to 378 nm by 38.0 %. Consequently, the brittle defects and cutting force are significantly suppressed. It generates increased residual compressive stress, thereby further improving the machining quality.