RSM and MD—a roughness predictive model and simulation comparison of monocrystalline optical grade silicon

Abstract

Silicon is a major material for manufacturing high-quality optical components, a process requiring silicon roughness to be below 8 nm. Lately, the popular choice for manufacturing these high-quality components has been the use of single-point diamond on ultra-high precision machines. Diamond properties such as clear grain structure, low coefficient of friction, and well-defined grain structure are well harnessed in this process. To achieve the demanded roughness level, there is a need for an appropriate choice of machining conditions which does not only ensure ductile regime machining but also form a good starting point for an improved prediction. The present study varied three well-known strong determinants of surface roughness, namely, rake angle, nose radius, and feed rate, as design input factors to facilitate Ra prediction. One important discovery made that constitutes the novelty of this research which to the best of our knowledge has not been reported before is that high negative rake angle reduces the negative influence of high feed rate on surface roughness. Simulation was carried out using MD and the result was compared with the experiment. High form accuracy with Ra values between 1.8 and 7 nm, close approximation of actual turning/prediction results, and the conformity of MD and experimental results attested to the success of the research.