(1) Roughing stage. Most of the machining allowance of each machined surface is removed, and the fine reference is machined, and the main consideration is to increase 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 an appropriate finishing allowance, and complete the machining of the secondary surface at the same time.

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

(4) Finishing stage. It is mainly used to reduce the surface roughness value or strengthen the machined surface. It is mainly used for surface machining with high surface roughness requirements (ra≤0.32 μm).