The solution of shrinkage phenomenon in plastic mold injection processing

Injection molding products use many platforms, widely used in: aerospace, electronic and electrical, ships, automobiles, electrical appliances and other machine platforms, especially a few relatively good function of plastic, after molding injection molding, some of the function of the product is even better than a few metal, which is why a lot of products selected injection parts for the sake of.

Injection molding process involves: plastic particles, injection mold planning and production, injection molding machine, injection molding technician and so on, any joint can not appear problems, otherwise it is very easy to lead to injection molding products.

Thermosetting plastic materials are characterized by extension after temperature rise, contraction after cooling, and gradually reduced volume after natural pressure. In the injection molding process of plastic mold, the molten plastic is injected into the cavity first, and after filling, the wear-resistant material is cooled and solidified, and the plastic parts shrink when they ejection from the plastic mold, which is called molding shrinkage. From the removal of plastic molds to the cooling era, specifications will still have a small change, one of which is to shrink again, known as post-shrinkage.

Injection molding

When a plastic mold is molded by injection, the shrinkage in the thick side of the plastic mold layout (such as the rib or rise) is more severe than in the adjacent side, because the cooling rate in the thick side is much slower than that in the thin side. Differential cooling rates can create indentations in the sustained surface, also known as shrinkage marks. This defect endangers the quality of processing and production, especially for large and medium-sized thin-walled products, such as TV slanted cases and display cases.

For products requiring strict appearance quality, traces of shrinkage should be removed, while a few products with lower technical function, such as small toys, are allowed to have traces of shrinkage.

To deal with such problems, consider the processing skills of plastic molds, geometric patterns of parts, the selection of raw materials and injection molding plans. Adjusting the working pressure and time of the injection is another technique for dealing with shrinkage problems.