A CNC workpiece often has several surfaces to be machined. These surfaces not only have certain accuracy requirements, but also have certain position requirements between the surfaces. In order to achieve these accuracy requirements, the machining sequence of each surface of CNC machining parts can not be placed casually, but must be in accordance with the positive principle, that is, the selection and conversion of the positioning benchmark determines the processing sequence, and the principle that the previous process plans the positioning benchmark for the subsequent process.
1. Before the important surface machining, the precision datum should be trimmed once to ensure the machining accuracy of the important surface.
2. After finishing the fine datum machining, rough machining, semi finish machining and finish machining shall be carried out for the key surfaces with high precision requirements. The surface with unique high precision also needs finishing.
3. The surface used as the precision reference should be machined at the beginning of the CNC machining process, because it should be used to locate other surfaces in the subsequent process. That is, “benchmark before others”.
4. When machining the fine datum, it is necessary to use the coarse datum for positioning. In the process of single piece, small batch production and even batch production, for castings and forgings with complex form or large size, and workblanks with large size deviation, the marking process shall be arranged before the machining process, so as to provide the alignment benchmark for the precision machining.
5. As for the simple process of waste products, finishing and finishing can be properly placed in the front, and some secondary small surface processing can be placed later.
