According to the structure of the part, the state of the blank and the needs of positioning and clamping, the arrangement of the CNC machining sequence is considered, and the rigidity of the workpiece is emphasized. The sequence of procedures should generally follow the following principles:
1: Basic priority principle
At the beginning of machining, the base surface is machined first, because the more accurate the base surface, the smaller the clamping error, so any CNC precision parts must be roughed, semi-finished, and finished when necessary. For example: box parts generally process the positioning plane and two positioning holes first, and then process the hole system and other planes with the plane and positioning holes as the fine reference. The principle of improving machining accuracy is to arrange the machining of the base surface and the main surface.
2: thick first and then thin
The processing sequence of each surface is processed in the order of rough processing and finishing, so as to gradually improve the precision of the processed surface and reduce the surface roughness.
3: The principle of priority
The accuracy of the part surface and assembly surface is high, and it belongs to the main surface, which should be processed first, so as to detect possible defects on the main surface of the blank as early as possible. For surfaces such as empty surfaces, keyways, closed screw holes, and smooth empty surfaces, the accuracy requirements are not high, and they belong to secondary surfaces, which can be interspersed. Generally, finishing is arranged after the main processing surface reaches a certain accuracy.
4: The principle of front and back
For boxes, brackets, and body parts, the plane dimensions are relatively large, and the dimensions are usually the surface to be processed first, and the hole to be processed later. Therefore, on the one hand, it is stable and reliable to use the machined plane for positioning; on the other hand, it is easier to machine holes on the machined plane, and can improve the machining accuracy of the hole, especially when drilling, the hole axis is not easy to tilt.
5: Preconceived principles
That is to say, the inner cavity processing process is carried out first, and then the external shape processing process is carried out.
6: The processing of the previous process does not affect the positioning and clamping of the next process.
7: It is best to use the same installation method or the same tool processing process continuously to reduce the number of repeated positioning.
8: When performing multiple processes in the same installation process, the process with less damage to the rigidity of the workpiece should be arranged first. In addition, when arranging the CNC machining sequence, pay attention to the arrangement of the undercut, chamfering and other operations.