When machining parts on a numerical control machine, there are generally two situations. The first situation: there are parts drawings and blanks, and a numerical control machine tool suitable for machining the part should be selected. The second situation: there is already a numerical control machine tool, and the parts suitable for machining on the machine should be selected. In either case, the main factors to be considered are the material and type of blanks, the complexity of the contour shape of the parts, the size, machining accuracy, the number of parts, heat treatment requirements, etc. In summary, there are three points: ① To ensure the technical requirements of the processed parts and process qualified products. ② It is conducive to improving productivity. ③ Reduce production costs (processing costs) as much as possible.