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Summary of our CNC processing experience

CNC machining is usually refers to the computer digital control of precision machining, also known as numerical control machining. CNC processing is controlled by computer after programming and processing, therefore, CNC processing has the advantages of stable processing quality, high processing accuracy, high repetition accuracy, processing complex surface and high processing efficiency. In the actual processing process, human factors and operation experience, to a large extent, will affect the final processing quality. In this regard, this article summarizes ten experiences on CNC processing.

What principles should be followed in arranging the CNC processing sequence?

The arrangement of processing sequence should be considered according to the structure of the parts and the blank condition, as well as the need of positioning clamping, the focus is that the rigidity of the work-piece is not destroyed. The sequence shall generally be conducted according to the following principles:

1.The best to connect with the same positioning, clamping mode or the same knife CNC processing process, in order to reduce the repeated positioning times, knife change times and moving plate times.

2.In the same installation of multiple processes, should first arrange the rigid damage of the work-piece process.

3.The CNC processing of the last process can not affect the positioning and clamping of the next process, and the general machine tool processing process should also be considered comprehensively.

4.The first internal cavity plus process, and then the shape processing process.

How to divide the CNC processing process?
Generally, the CNC machining process can be divided according to the following methods: the processing part sequence method for CNC processing content a lot of parts, according to its structural characteristics of the processing part into several parts, such as inner shape, shape, surface or plane. Generally, process the plane and the positioning surface before machining the simple geometry shapes and then the complex geometry shapes; the parts with low accuracy and the parts with high accuracy.

2.The tool centralized sequence method is to divide the process according to the tool used, with the same tool CNC processing parts on all the parts that can be completed. At the other parts that they can do with the second knife and the third one. This can reduce the number of knife changes, compress the empty-range time, and reduce the unnecessary positioning error.

3.With coarse, fine CNC processing sequence method for CNC processing deformation parts, due to the deformation may occur after rough processing and need to adjust the shape, so generally speaking, all to rough, fine processing to separate the process. To sum up, in the division of the process, we must depend on the structure and process of the parts, the function of the machine tool, the number of parts CNC processing content, installation times and the production organization of the unit flexible grasp. In addition, it is suggested 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.

What should be paid attention to when determining clam method?
The following four points should be paid to when determining the positioning reference and clamping scheme:

1.Try to reduce the number of clamping, as far as possible to CNC processed after a positioning.

2.Avoid the use of the manual adjustment scheme.

3.Strive to unify the benchmark of design, process and programming calculation.

4.the fixture to open free, its positioning, clamping mechanism can not affect the CNC processing in the knife (such as collision), encounter such cases, can use the vice or bottom plate screw to install the clip.

What are the principles of setting the security height in programming?
The principle of setting the safety height: generally higher than the highest surface of the island. Or set the programming zero in the highest surface, so that you can also avoid the danger of knife collision.

How to choose the knife route?

The knife route is the trajectory and direction of the tool relative to the processed piece in the process of exponential control. The reasonable selection of the processing route is very important, because it is closely related to the CNC machining accuracy and surface quality of the parts. In determining the knife route, the following points are mainly considered:

1.Convenient for numerical calculation and reduce the programming workload.

2.Seek the shortest CNC processing route and reduce the time of empty knife to improve the CNC processing efficiency.

3.Reduce the number of program segments.

4.Ensure the machining accuracy requirements of the parts.

5.Ensure the roughness of the CNC surface of the work-piece contour after processing, and the final outline should be arranged for the last blade.

6.The tool advance and retreat knife (cutting in and cutting out) route should also be seriously considered, to minimize the stop knife at the outline (sudden change of cutting force causes elastic deformation) and leave knife marks, but also to avoid vertical cutting knife on the contour surface and cut the work-piece.

How to choose a reasonable processing tool? How many materials are available? How to determine the tool speed, cutting speed, cutting width?

1.The plane milling should be selected with not heavy grinding carbide end milling cutter or vertical milling cutter. General milling, as far as possible to use the second walking knife processing, the first walking blade best with the end milling cutter rough milling, along the surface of the work-piece continuous walking knife. The width of each blade is recommended to 60% -75% of the tool diameter.

2.vertical milling cutter and cemented carbide blade end milling cutter is mainly used for processing convex platform, groove and box mouth surface.

3.Ball knife, round knife (also known as round nose knife) is often used in processing surface and oblique profile. The ball knife is mostly used for semi-finishing and finishing. Round knives with carbide tools are mostly used for opening thickness.

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