CNC machining experience sharing (Part 2)

20. Common problems encountered in the die after processing:

The cutting tool should be made of the same material as that of the large one. The back die drawing is usually made of Copper drawing, which is made by reducing the material level plus PL surface, pillow position and the original body. If the material level is relatively uniform, negative material level can be directly reserved in the processing information, but pl (parting surface), pillow position and impact surface can not shrink the material level. At this time, you can first correct these surfaces by a material level or draw a section. One of the problems encountered by the original body department is that the ball knife can not clear the sharp angle. At this time, the flat knife can be used to process the sharp angle of the curved surface. For example, if the inlay section is used, the back mold is divided into the hidden frame and the core. When adding the Tibetan section, pay attention to the empty knife several times, otherwise the frame will have a slope, the upper edge is accurate, and the lower side is small, so it is difficult to match the mold. Especially for the deeper frame, we must pay attention to this problem, and the smooth frame knife should be new and good And choose a larger knife. If the core is too high, you can turn it over to process the frame, and then assemble it into the frame, and then process the shape. Sometimes there is a branch mouth. Be careful not to over cut. When using a ball knife to polish the shape, you must protect the edge steps. In order to facilitate the matching mode, the frame size can be smaller than the overall dimension of the core-0.02/s, and the tolerance and step distance of the core optical knife can be slightly larger, the tolerance is 0.01 ~ 0.03, and the feed is 0.2 ~ 0.5.

21. Problems in bulk copper processing:

Sometimes it is difficult to process the whole copper male, there is a dead angle that cannot be processed, or it is difficult to process. If the required tool is too long or too small, it can be considered to divide another copper male. Sometimes, it is necessary to clear the angle clearing copper male. However, it is not difficult to process this kind of copper male. However, it is necessary to make sure the deviation of flame time and check the benchmark.

22. Processing of thin disk copper male:

This kind of copper male is easy to be opened during processing. A new knife should be used. The knife should be small and the feed should not be too large. When processing, the length a should be set correctly, but D should be left with a large allowance (such as 1.0 mm) and then walk on both sides. Each time, the depth h = 0.2 ~ 1. The depth feed should not be too much, nor should it be moved around the knife, but should be divided into two sides.

23. Direction of left and right parts and one out two parts:

Sometimes a set of mold will produce two parts, for the left and right parts, the graphics can be produced by mirror. If two identical parts are produced, the figure must be balanced or rotated in XY, and must not be mirrored. Be careful not to reverse the direction.

24. CNC machining direction:

The four guide bolt holes of the die are not completely symmetrical, and one of them is asymmetric. Therefore, it is not clear when processing the front and rear dies. There is a benchmark on each template. When the front and rear dies are closed, they must be based on the datum, especially on the original die. When drawing, pay attention to the direction. The direction of the copper male is consistent with that of the front view (top view), the direction of the core of the family and the frame of the Tibetan family is the same as that of the copper male, while the direction of the front model is opposite. Some decorative lines such as grooves or boss on the surface are not easy to process because they are relatively narrow. For the groove, we generally avoid the groove empty, that is, milling deeper, and then add a loose male to make the sink surface. Generally, the boss can only be made into a loose joint separately, and the large copper male can not be made, so as to ensure the quality.

25. Fitting tolerance of mould and product:

A set of products usually has several or more than ten parts. The main matching dimensions of these parts are guaranteed by computer gong processing. It is very important to select reasonable tolerance, especially some product design drawings do not consider the matching problem. For the fit of bottom and surface shell, the shape is no doubt 0-0 fit, and the positioning is guaranteed by the support mouth. The tolerance of concave and convex support is generally 0.1 mm, single side. The shape of the accessories on the large body, such as transparent mirror, is 0.1 ~ 0.2 smaller than the size of the large body. The shape of the movable parts on the large body, such as buttons, is 0.1 ~ 0.5 smaller than that of the large body. The surface shape of the accessories on the big body should be consistent with the surface shape of the large body, and it can come down from the surface of the body.

26. Draft angle (draft angle)

Plastic mold must be made to the mold slope, otherwise it will be scratched. If the drawing does not indicate, you can consult with the mold maker. The mold angle is generally 0.5 ~ 3 degrees. If the etched mold, the mold angle should be larger, 2 ~ 5 degrees, depending on the thickness of the etch.

27. Cutting problem:

Most of the time, when the blade is just milled, the cutting amount is relatively large, which is easy to cause the knife to break and snap. At this time, you can first open the lower cutter position, or lift the knife away, or cut the knife outside the material in the daytime. In short, we should fully consider this problem. When the processing capacity is relatively large, the knife clip is too long and the knife is too small. It is easy to happen when the processing amount is relatively large, especially when there are more concentration feed. For example, if the smooth side depth h = 50 mm and the diameter is 3 / 4 cutter, we can process it in 25 mm twice, which is not easy to happen. If the tool holder is too long, the length of the tool installation is very important for processing. It should be as short as possible. Beginners can easily ignore this problem. The clamping length of the tool must be marked on the program paper. It is easy to grab the knife when turning the corner. The solution is to clean the corner with a smaller knife layer by layer, and then change the large knife to smooth the side. For the semicircular groove with diameter 8 as shown in the figure, if it is directly processed with R4 cutter, the cutting position is easy to grab the knife. The solutions are: (1) use R3 to scan the tool path; (2) use R3 to roughen first, and finally use R4 knife to clear the angle.