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How to avoid plastic mould deformation


Plastic molds are an important tool for the production of plastic products. They can give the plastic products a complete configuration and precise size. When the plastic mold is deformed, it will directly affect the quality of the plastic products, so we need to pay special attention.

1. For symmetrical plastic molds, the deformation tendency can be considered according to the cavity size, outer dimensions and height. When the wall of the mold is thin and the height is small, it is easier to harden, and it is also possible that the tissue stress plays a major role. Therefore, the cavity tends to expand. Conversely, if the wall thickness and height are large, it is not easy to harden. At this time, it may be the main role of thermal stress. Therefore, the cavity tends to shrink. What is said here is the general trend. In the production practice, it is necessary to consider the specific shape of the part, the steel type used and the heat treatment process, etc., and continue to summarize the experience through practice. Due to the actual production, the outer dimensions of the mold are often not the main working size, and can be corrected by grinding after deformation, so the above analysis is mainly the deformation trend of the cavity.

2. For the deformation of the asymmetric mold, it is also the result of the combined effects of thermal stress and tissue stress. For example, for a thin-walled mold, since the mold wall is thin, the internal and external temperature difference during quenching is small, and thus the thermal stress is small; but it is easy to be hardened and the tissue stress is large, so the deformation tends to expand the cavity.

3. In order to reduce the deformation of the mold, the heat treatment department should work together with the mold design department to improve the mold design, such as avoiding the mold structure with different cross-sectional dimensions as much as possible, the shape of the mold to strive for symmetry, and the complex structure of the mold.

4. When the shape of the mold cannot be changed, in order to reduce the deformation, some other measures can be taken. The overall consideration of these measures is to improve the cooling conditions so that the parts are evenly cooled; in addition, various coercive measures can be assisted to limit the quenching deformation of the parts.