Research on the high-quality, low-wear single point diamond turning process of single crystal germanium

Single crystal germanium, which is a typical infrared optical crystal used for aerospace and astronomy applications due to their excellent mechanical, optical, and chemical property is difficult to obtain super smooth surface in ultra-precision turning and easy to cause tool wear owing to its inherent brittleness and hardness. In the processing process of single crystal germanium optical elements, good surface roughness is beneficial to improve the diffraction efficiency of single crystal germanium, while small cutting force can effectively lower the diamond tool wear caused by high hardness of germanium. In this paper, the single variable method is used to study the influence of the main factors in the single point diamond turning process on the surface roughness and cutting force of single crystal germanium, including spindle speed back cutting depth and feed. The experimental results are used to guide the machining process of the single crystal germanium diffraction surface, and the appropriate process parameters are selected to perform ultra-precision turning on the single crystal germanium with a very small cutting force to obtain a sub-nanometer ultra-smooth surface to improve the diffraction efficiency and reducing tool wear.