What is CNC machining


Author: MULAN -Plastic Molding Manufacturer

CNC machining, also called numerical control machining, refers to the processing performed with numerical control processing tools. Because CNC machining is controlled by computer after programming, CNC machining has the advantages of stable processing quality, high processing accuracy, high repeatability, complex surface processing, and high processing efficiency. In the actual processing process, human factors and operating experience will largely affect the final processing quality.

Next, let us take a look at the twelve valuable experiences summed up by an old driver with ten years of CNC processing experience... 1 How to divide the CNC processing procedures in Shanghai? The division of CNC machining processes can generally be carried out in the following ways: The tool concentration and sequencing method is to divide the process according to the tool used, and use the same tool CNC to process all the parts that can be completed on the part. In other parts that they can finish with the second knife and the third. In this way, the number of tool changes can be reduced, the idle time can be compressed, and unnecessary positioning errors can be reduced.

For parts with a lot of CNC processing content, the processing parts can be divided into several parts according to their structural characteristics, such as inner shape, shape, curved surface or plane. Generally, the plane and positioning surface are processed first, and then the holes are processed; the simple geometric shapes are processed first, and then the complex geometric shapes are processed; the parts with lower precision are processed first, and then the parts with higher precision requirements are processed. The rough and fine CNC machining sequence method is used for parts that are prone to CNC machining deformation. Due to the possible deformation after rough machining, it is necessary to correct the shape.

To sum up, when dividing the process, it is necessary to flexibly grasp the structure and manufacturability of the parts, the function of the machine tool, the content of the CNC machining of the parts, the number of installations and the production organization of the unit. In addition, it is 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 cnc 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 need for positioning and clamping. The key point is that the rigidity of the workpiece is not damaged.

The sequence should generally be carried out according to the following principles: the cnc processing of the previous process cannot affect the positioning and clamping of the next process, and the processing process of general machine tools interspersed in the middle should also be considered comprehensively. The internal shape and cavity processing process is carried out first, and then the shape processing process is carried out. The same positioning and clamping method or the same tool cnc machining process are connected to reduce the number of repeated positioning, the number of tool changes and the number of moving the pressure plate.

For multiple processes in the same installation, the process with less rigid damage to the workpiece should be arranged first. 3 What aspects should be paid attention to when determining the workpiece clamping method? The following three points should be paid attention to when determining the positioning datum and clamping scheme: strive to unify the datum of design, process, and programming calculation. Minimize the number of clamping times, and try to achieve all the surfaces to be processed by cnc after one positioning.

Avoid using manual adjustment schemes that occupy the machine. The fixture should be open, and its positioning and clamping mechanism cannot affect the tool movement in cnc machining (such as collision). When encountering such a situation, it can be clamped by using a vise or adding a bottom plate to draw screws. 4. How to determine the reasonable point of tool setting? 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 the reference position or the part that has been finished. Sometimes the tool setting point is destroyed by cnc after the first process, which will cause the second process There is no way to find the tool setting points in the process and after that, so when setting the tool in the first process, pay attention to setting up a relative tool setting position at a place that has a relatively fixed size relationship with the positioning reference, so that it can be retrieved according to the relative positional relationship between them. Original tool setting point.

This relative tool setting position is usually set on the machine tool table or fixture. The selection principle is as follows: it is easy to find the alignment. Easy to program.

The tool setting error is small. It is convenient and can be checked 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 zero point of the machine tool.

Once the workpiece coordinate system is fixed, it generally does not change. The workpiece coordinate system and the programming coordinate system must be unified, that is, the workpiece coordinate system and the programming coordinate system are consistent during processing. 5 How to choose the cutting route? The tool path refers to the movement track and direction of the tool relative to the workpiece during NC machining.

The reasonable choice of processing route is very important, because it is closely related to the cnc processing accuracy and surface quality of the parts. The following points are mainly considered when determining the cutting route: to ensure the machining accuracy requirements of the parts. It is convenient for numerical calculation and reduces programming workload.

Seeking the shortest cnc processing route, reducing the empty tool time to improve cnc processing efficiency. Minimize the number of program segments. To ensure the roughness of the workpiece contour surface after cnc machining, the final contour should be processed continuously in the last one pass.

The cutting and retreating (cutting in and out) route of the tool should also be carefully considered to minimize the tool marks left by stopping the tool at the contour (sudden change of cutting force causes elastic deformation), and avoid cutting the knife vertically on the contour surface. Scratch the workpiece.

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