(1) Roughing stage. Most of the machining allowances of each machining surface are removed, and the precision benchmark is machined, and the primary consideration is to improve the productivity as much as possible.

  (2) Semi-finishing stage. To remove the defects that may occur after rough machining, to prepare for the finishing of the surface, it is required to achieve a certain machining accuracy, ensure the appropriate finishing allowance, and complete the machining of the non-essential surface together.

  (3) Finishing stage. At this stage, a large cutting speed, small feed and cutting depth are selected to remove the finishing allowance left by the previous process, so that the surface of the part can meet the technical requirements of the drawing.

  (4) Finishing stage. It is mainly used to reduce the surface roughness value or strengthen the processed surface, and it is mainly used for surface processing with high surface roughness requirements (ra≤0.32μm).

  (5) Ultra-fine processing stage. The processing accuracy is 0.1-0.01μm, and the surface roughness value is ra≤0.001μm. The main processing methods are: fine cutting, fine mirror grinding, fine grinding and polishing.