CNC numerical control processing programming refers to the automatic generation of numerical control processing with the support of a computer and corresponding computer software system The course of the program. It gives full play to the fast calculation and storage functions of the computer.

1. The principle of rough first and refined later

The processing sequence of each surface is carried out in the order of roughing, semi-finishing, finishing and finishing, with the purpose of gradually improving the accuracy and surface quality of the processed surface of the part. If all surfaces of the part are processed by CNC machine tools, the process arrangement is generally carried out in the order of roughing, semi-finishing, and finishing, that is, semi-finishing and finishing are performed after all roughing is completed. During rough machining, most of the machining allowance can be quickly removed, and then each surface can be finished in turn, which can improve production efficiency and ensure the machining accuracy and surface roughness of the parts. This method is suitable for machined surfaces that require high position accuracy. This is not absolute. For example, for some machined surfaces that require high dimensional accuracy, considering the rigidity, deformation and dimensional accuracy of the parts, these machined surfaces can also be considered in the order of rough machining, semi-finishing, and finishing. Finish. For machining surfaces with high precision requirements, it is best to leave the parts for a period of time between roughing and finishing processes, so that the surface stress of the parts after roughing can be completely released, and the degree of stress and deformation on the surface of the parts can be reduced, which is beneficial to improve The machining accuracy of the parts.
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2. The principle of face first and hole second

For box, bracket, machine body and other parts, the plane outline size is larger, and the plane positioning is more stable and reliable, so the plane should be processed first, and then the hole should be processed. In this way, not only the subsequent processing has a stable and reliable plane as the positioning reference surface, but also the processing of holes on a flat surface makes the processing easier, and it is also conducive to improving the processing accuracy of the holes. Generally, the processes can be divided according to the processing positions of the parts. Generally, simple geometric shapes are processed first, and then complex geometric shapes; the lower precision parts are processed first, and then the higher precision parts are processed; the plane is processed first, and the hole is processed later.
3. The principle of processing datum plane first

At the beginning of processing, the surface used as the finishing reference is always machined. Because the surface of the positioning reference is accurate, the clamping error is small, so the processing of any part is always roughing the positioning reference surface first And semi-finishing, finishing if necessary, for example, shaft parts are always roughing and semi-finishing the positioning reference surface, and then finishing. For example, shaft parts always machine the center hole first, and then machine the hole system and other surfaces based on the center hole surface and the positioning hole as a precision reference. If there is more than one precision datum surface, the processing of the datum surface should be arranged in accordance with the order of datum conversion and the principle of gradually improving the processing accuracy.

4. The principle of first inside and then outside

For precision sleeves, the coaxiality between the outer circle and the hole is required. Generally, the principle of hole first, outer circle is adopted, that is, the outer circle is used as the positioning reference to machine the hole, and then the hole with higher precision is used as the positioning The outer circle is processed by the datum, which can ensure that the outer circle and the hole have high coaxiality requirements, and the fixture structure used is also very simple.

5. The principle of reducing the number of tool changes

In CNC machining, the machining sequence should be arranged as far as possible according to the order in which the tool enters the machining position.