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Commonly Used CNC Machining Programming Skills

29   |   Published by VMT at Aug 10 2021

When we start CNC machining programming, we first consider the process division, machining sequence, workpiece clamping and tool setting points. Next, VMT will lead you to understand the common skills of CNC machining programming.



How to divide the process of CNC machining parts? 



CNC machining parts process division: tool centralized division process method, CNC machined parts division process method, rough machining and finishing division process method.


Generally, it can be carried out according to the following methods:


A. The tool centralized ordering method is to divide the processes according to the tools used, and use the same tool to CNC machine all the positions that can be completed on the part. Use the second knife and the third knife to complete other positions they can complete. This can reduce the number of tool changes, reduce idle time, and reduce unnecessary positioning errors.


B. According to the NC machining parts ordering method, for parts with many machining positions, the NC machining parts can be divided into several parts according to their internal shape, external shape, curved surface or plane and other structural features. Generally, the plane and positioning surface are processed first, and then the hole is processed; the simple geometric shape is processed first, and then the complex geometric shape is processed; the position with lower precision is processed by CNC first, and then the position with higher requirements is processed.


C. Sequential method for roughing and finishing. For parts that are prone to deformation in CNC machining, calibration may occur because they may be deformed after rough machining. Therefore, generally speaking, all roughing and finishing processes must be separated.

In summary, when dividing processes, we must flexibly grasp the structure and manufacturability of parts, the functions of machine tools, the number of CNC machined parts, the number of devices, and the production organization of the unit. It is also recommended to adopt the principle of process concentration or process dispersion, which should be determined according to the actual situation, but should be reasonable.



Commonly Used CNC Machining Programming Skills




What aspects should be paid attention to in the clamping method of CNC machining parts?




The following three points should be paid attention to when determining the positioning datum and clamping plan:


1. Unified design, technology and calculation benchmarks for CNC machining programming.

2. Minimize the number of clamping times to ensure that the machined surface can be processed after one positioning.

3. Avoid using manual adjustment schemes.

4. The fixture should be opened smoothly, and its positioning and clamping mechanism should not affect the cutting (such as collision) during processing. In this case, use a vise or add a base plate to pull the screw.





3. How to make sure that the tool setting point of CNC machining programming is more reasonable?



a.When setting the tool, please note that the tool setting point must be the reference position or the position where the finishing has been completed. Sometimes the tool setting point is processed and damaged after the first process, which will cause the second process and subsequent tool setting. There is no way to find the tool set point. Therefore, in the first process of tool setting, pay attention to setting a relative tool setting position that has a relatively fixed size relationship with the positioning reference, so that the tool point can be calibrated according to the distance between the tool points. This relative tool setting position is usually set on the machine tool table or fixture.


The selection principles are as follows:

1) Easy to align.

2) Easy to program for CNC machining.

3) The tool setting error is small.

4) It is convenient to check during CNC machining.



b. The origin position of the coordinate system of the CNC machining parts is set by the operator. It is determined by the tool setting after the workpiece is clamped. It reflects the distance position relationship between the workpiece and the machine zero point. Once the workpiece coordinate system is fixed, it generally does not change. The workpiece coordinate system and the data processing programming coordinate system must be unified, that is, the workpiece coordinate system is consistent with the programming coordinate system during processing.





How to choose the knife route?



The tool path is the movement path of the tool to the workpiece in the CNC machining process. The reasonable choice of machining route is very important, because it is related to the machining accuracy and surface quality of CNC machined parts. When determining the path of the tool, the following points are mainly considered:


1. Ensure the accuracy requirements of CNC machining of parts;

2. It is convenient for numerical calculation and reduces the workload of p process;

3. Seek the shortest machining route, reduce the time of empty tool, and improve the efficiency of CNC machining;

4. Try to reduce the number of CNC machining program segments;

5. Ensure the roughness requirements of the contour surface of the workpiece after processing. The final contour should be arranged at the end and processed continuously at one time;

6. The advance and retreat (cut-in and cut-out) route of the tool should also be considered to minimize tool stoppage (elastic deformation caused by sudden changes in cutting force) and knife marks. Also avoid cutting the workpiece vertically on the contour surface to cause scratches on the CNC machined parts.





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