Shape Heat Treatment Of Plastic Bottle Cap Capping Machine

The influence of the heat treatment deformation of the plastic mold geometry of the plastic bottle cap capping machine is actually acted on by the thermal stress and the tissue stress. Due to the various shapes of plastic molds, it is still difficult to summarize the exact deformation laws.

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

The deformation of the asymmetric mold by the plastic bottle cap capping machine is also the result of the combined effect of thermal stress and tissue stress. For example, for a thin-walled and thin-sided mold, because the mold wall is thin, the temperature difference between the inside and the outside is small during quenching, so the thermal stress is small; but it is easy to be quenched and the structure stress is large, so the deformation tends to expand the cavity.

In order to reduce the deformation of the mold, the heat treatment department should work with the mold design department to improve the mold design, such as avoiding mold structures with large differences in cross-sectional size, symmetrical mold shapes, and split structures for complex molds.

When the plastic bottle cap capping machine cannot change the shape of the mold, in order to reduce the deformation, some other measures can be taken. The general consideration of these measures is to improve the cooling conditions so that each part can be cooled uniformly; in addition, various compulsory measures can also be assisted to limit the quenching deformation of the parts. For example, adding process holes is a measure for uniform cooling of all parts, that is, opening holes in some parts of the mold, so that all parts of the mold can be uniformly cooled to reduce deformation. It can also be wrapped with asbestos around the mold that is easy to expand after quenching to increase the cooling difference between the inner hole and the outer layer and shrink the cavity. Retaining ribs or reinforcing ribs on the mold is another compulsory measure to reduce deformation. It is especially suitable for die with swelling cavity and die with notch that is easy to expand or shrink.