Tool design and surface roughness optimization for novel in-situ laser-assisted diamond turning of single-crystal germanium

As a typical hard-and-brittle material, single-crystal germanium is characterized by inferior surface integrity and suboptimal material removal efficiency when subjected to conventional single point diamond turning. In contrast, in-situ laser-assisted turning (LAT) has demonstrated superior performance in achieving smooth surface machining of single-crystal germanium. In this study, a novel diamond tool and laser-assisted heating method were developed, in which the laser beam is refracted at the rake face and cutting edge and undergoes total internal reflection (TIR) at the flank face, thereby enhancing laser utilization efficiency. The effect of laser power on temperature distribution during in-situ LAT was investigated through thermo-mechanic coupled finite element cutting simulations. Using surface roughness as the response variable, optimal machining parameters for in-situ LAT of single-crystal germanium were determined via response surface methodology: laser power of 10 W, spindle speed of 2492 rpm, feed rate of 1.64 μ m rev –1 , and depth of cut of 1.50 μ m. Under these optimized conditions, the predicted minimum surface roughness was 10.28 nm, representing a 67.54% reduction compared to the maximum experimental value.