In the injection molding process, the cooling process plays a very important role in the quality of the molding, because it directly affects the production efficiency of the injection molding and the intrinsic performance and apparent quality of the injection molded product.
The excellent cooling system can significantly reduce the cooling time, shorten the injection cycle, reduce the residual thermal stress and warpage of the product, and enhance the mechanical properties and internal and surface quality of the product. If the injection molded article is unevenly cooled, thermal residual stress is generated, which has a serious influence on the shape, size, and performance of the injection molded article.
Tests have shown that the thermal residual stress of the injection molded parts is at least an order of magnitude larger than the flow residual stress. Therefore, in the injection molding process, the factors affecting the thermal residual stress should be mainly considered.
When the viscoelastic polymer melt is cooled below the glass transition temperature in the mold, uneven density changes and uneven temperature changes will form thermal residual stresses. In the injection molding process, the thermal residual stress is easily generated in the following two stages: one is the cooling stage of the injection molded article in the cavity, and the other is the stage in which the injection molded article is cooled from the demolding temperature to the room temperature. Therefore, in order to achieve high-efficiency production and obtain excellent injection molded articles, the mold must be temperature-regulated.
In the injection mold, the cooling effect of the mold is related to the production efficiency and the quality of the final injection molded product. Therefore, the design of the cooling system is one of the key issues to be considered in the mold design process. However, due to the limited means of mold manufacturing at the present stage and the lack of suitable cooling channel design theory, the design and manufacture of the cooling water circuit can only be limited to a relatively simple structure.