The Sooner You Know These CNC Machining Experiences, The Better

Due to the complexity of CNC machining (such as different machine tools, different materials, different cutting tools, different cutting methods, different parameter settings, etc.), to reach a certain level of CNC machining/programming, it must go through a relatively long period of time. The following content is a summary of CNC machining technology, procedures, selection of commonly used tool parameters, monitoring during machining, etc., based on the engineers' long-term actual production experience, for your reference.

1. How to divide the processing procedure?

The division of CNC machining processes can generally be carried out according to the following methods:

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

(2) According to the processing part order method, for parts with a lot of processing content, the processing part can be divided into several parts according to its structural characteristics, such as inner shape, shape, curved surface or plane. 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 parts with lower precision are processed first, and then the parts with higher precision are processed.

(3) For parts that are prone to processing deformation by roughing and finishing ordering method, due to the deformation that may occur after roughing, the shape needs to be adjusted, so in general, all the rough and finishing processes must be separated. .

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

2. What principles should be followed in the arrangement of the processing sequence?

The arrangement of the processing sequence should be considered according to the structure of the part and the condition of the blank, as well as the needs of positioning and clamping. The important point is that the rigidity of the workpiece is not destroyed. The order should generally be carried out according to the following principles:

(1) The processing of the previous process cannot affect the positioning and clamping of the next process, and the general machine tool processing processes should also be considered comprehensively.

(2) Carry out the inner cavity adding process first, and then the outer shape processing process.

(3) It is best to connect the processes of machining with the same positioning, clamping method or the same tool to reduce the number of repeated positioning, tool changes and the number of times of moving the platen.

(4) For the multiple procedures carried out in the same installation, the procedure should first be arranged with less rigid damage to the workpiece.

3. Which aspects should be paid attention to when determining the clamping method of the workpiece?

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

(1) Strive to unify the design, process, and programming calculation benchmarks.

(2) Minimize the number of clamping times, as far as possible to be able to process all the surfaces to 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 knife during processing (such as collision). In such a situation, use a vise or add a bottom plate to draw a screw.

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4. How to determine the tool setting point is more reasonable? What is the relationship between the workpiece coordinate system and the programming coordinate system?

1. The tool setting point can be set on the part to be processed, but note that the tool setting point must be a reference position or a part that has been processed. Sometimes the tool setting point is destroyed after the first process, which will cause the second process and There is no way to find the subsequent tool setting points. Therefore, in the first process of tool setting, pay attention to setting up a relative tool setting position where there is a relatively fixed size relationship with the positioning datum, so that the original position can be retrieved according to the relative position relationship between them. Knife point. This relative tool setting position is usually set on the machine tool table or fixture. The selection principles are as follows:

① Easy to find.

②Easy to program.

③The tool setting error is small.

④ It is convenient to check during processing.

2. The origin position of the workpiece coordinate system is set by the operator. It is determined by 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 is generally not changed. The workpiece coordinate system and the programming coordinate system must be unified, that is, during processing, the workpiece coordinate system and the programming coordinate system are the same.

5. How to choose the knife route?

The path of the tool is the path and direction of the tool relative to the workpiece in the index control process. The reasonable choice of the processing route is very important, because it is closely related to the processing accuracy and surface quality of the parts. The following points are mainly considered when determining the path of the knife:

①Ensure the machining accuracy requirements of the parts.

②It is convenient for numerical calculation and reduces the workload of programming.

③ Seek the shortest processing route, reduce the empty tool time to improve processing efficiency.

④ Reduce the number of blocks as much as possible.

⑤Ensure the roughness requirements of the workpiece contour surface after processing, and the final contour should be processed continuously in the last pass.

⑥The path of the tool's advance and retreat (cut-in and cut-out) should also be carefully considered, to minimize stopping at the contour (a sudden change in cutting force causes elastic deformation) and leaving tool marks, and avoid cutting vertically on the contour surface And scratch the workpiece.

6. How to monitor and adjust during processing?

After the workpiece is aligned and the program is debugged, it can enter the automatic processing stage. In the automatic machining process, the operator should monitor the cutting process to prevent abnormal cutting from causing workpiece quality problems and other accidents.

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