Experimental study on in-situ laser-assisted diamond turning of single crystal germanium

Abstract

For typical optical crystals like silicon and germanium, conventional ultra-precision machining ensures high machining quality but significantly reduces efficiency. Consequently, in-situ laser-assisted turning has emerged as a viable alternative. This study focuses on the single crystal germanium (111) surface and establishes a temperature-dependent model for calculating the critical cutting thickness of ductile-to-brittle transition. Orthogonal experiments were conducted on in-situ laser-assisted turning, followed by variance analysis, signal-to-noise ratio analysis, and mean analysis of the post-machining surface roughness. The contribution of each machining parameter to reducing surface roughness is as follows: rake angle > laser power > spindle speed > feed rate > cutting depth. The optimized parameter combination identified is: rake angle of −35°, laser power of 10 W, spindle speed of 2000 r/min, feed rate of 1 μm/r, and cutting depth of 1 μm. Machining with these parameters reduced surface roughness by 22.4 % compared to conventional machining under the same conditions, resulting in a surface free of fractures and pits.