In the numerical control process analysis, the process analysis of the part drawing must be carried out to analyze whether the structural manufacturability of each processing part of the part conforms to the characteristics of the numerical control processing. The main contents include:

1. The dimensions of the part drawing should conform to the convenience of programming

In the numerical control processing drawing, it is advisable to use the same datum to cite the size or directly give the coordinate size. This marking method is not only convenient for programming, but also convenient for coordinating the setting and calculation of design benchmarks, process benchmarks, inspection benchmarks and programmed zero points.

2. The geometric element conditions of the contour structure of the part should be sufficient

When programming, define all the geometric elements that constitute the contour of the part. When analyzing a part drawing, it is necessary to analyze whether the conditions of various geometric elements are sufficient. If not, it is impossible to program or model the processed part.

Parts CNC Machining

3. Can the machining accuracy and dimensional tolerance required by the parts be guaranteed?

Although the machining accuracy of CNC machine tools is very high, but for some special situations, such as the processing of thin-walled parts, due to the poor rigidity of thin-walled parts, the cutting force generated during machining and the elastic retreat of the thin-wall are prone to vibration of the cutting surface. This makes it difficult to guarantee the thickness tolerance of the thin wall, and the surface roughness increases accordingly. According to practical experience, when the thickness of a thin wall with a larger area is less than 3mm, this issue should be fully paid attention to in the process.

4. Whether the geometric type and size of the inner contour and the outer contour of the part are uniform

In CNC programming, if the geometrical types of the inner contour and the outer contour of the part are the same or similar, consider whether they can be compiled in the same program to reduce the tool specifications and the number of tool changes as much as possible to reduce auxiliary time and improve processing efficiency. It should be noted that the diameter of the tool is often limited by the radius R of the inner contour arc.

5. Can the process structure design of the parts be processed with larger diameter tools?

The use of a larger diameter milling cutter for machining can reduce the number of tool passes and improve the rigidity of the tool. Not only the machining efficiency is improved, but the machining quality of the workpiece surface and bottom surface is also improved accordingly.

6. The fillet radius of the groove bottom of the milling surface of the part or the fillet radius r at the intersection of the bottom plate and the edge plate should not be too large

Because the large diameter of the milling cutter in contact with the milling plane is d=D-2r, where D is the diameter of the milling cutter. When D is constant, the fillet radius r (as shown in Figure (1), the larger, the poorer the ability of the end edge of the milling cutter to mill the plane, the lower the efficiency, and the worse the manufacturability. When r is large enough It is necessary to use a ball-end milling cutter for machining, which should be avoided. When D is larger and r is smaller, the area of ​​the milling plane of the end edge of the milling cutter is larger, and the ability to process the plane is stronger. Of course, the milling process is also The better. Sometimes, when the milling bottom surface area is larger and the bottom arc r is also larger, you can use two milling cutters with different r to cut in two times.

7. Uniform principle of guarantee benchmark

If the part is milled on one side and then reinstalled on the other side of the milling surface, because the datum is not uniform, the tool will often be poorly connected due to the reinstallation of the part, and the contour positions and dimensions on the front and back sides will be inconsistent after processing. Therefore, try to use the appropriate holes of the part itself or use the reference edge of the part contour or specially set process holes (such as adding process bosses on the blank or setting reference holes in the subsequent process to remove the margin, etc.) as the positioning reference. Ensure the accuracy of the relative position after two clamping processes.

8. Consider the deformation of parts

When the parts are deformed during the CNC milling process, not only the processing quality of the parts is affected, but sometimes, the phenomenon of knife jumping occurs. At this time, the processing technology of milling should be considered, and the rough and fine processing should be separated as much as possible or the method of symmetrical removal of margin should be adopted. Of course, it can also be solved by heat treatment….