1. To ensure precision machining accuracy. A large number of workpieces are subject to large cutting force, clamping force and heat, so they should be rough machined and finish machined respectively. Due to rough machining. It is easy to cause surface hardening and there is a large internal stress in the workpiece. If the finishing and rough machining are continuous, the precision of precision parts will be redistributed with the stress after finishing, and will be lost soon. For some parts with high machining accuracy. Low temperature annealing or aging treatment shall be carried out after rough machining and before finishing to eliminate internal stress

2. The main process of rough machining is to cut off most of the machining allowance. The rough machining machine tool only needs high-power and low-precision machining. Finishing requires more sophisticated machine tools. Rough and finish machining on different machine tools does not require higher machining accuracy. Therefore. It can not only give full play to the performance of the equipment, but also prolong the service life of precision machine tools.

3. Heat treatment is often required during machining. The arrangement of heat treatment process is as follows: in order to improve the cutting performance of metal. Usually before machining. In order to eliminate internal stress, such as annealing, normalizing, quenching and tempering, etc. For example, aging treatment and quenching and tempering treatment are generally carried out after rough machining and before finishing machining. In order to improve the mechanical properties of parts, carburizing, quenching and tempering are generally carried out after machining. If there is deformation after heat treatment, follow-up processing procedures must be arranged.