Effect Of Cooling Effect And Production Efficiency Of Injection Mold
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.
Despite this, mold designers are still working to improve the cooling efficiency of the cooling system. Different types of water channels, such as spiral type, baffle point cooling type and screw plug type, are proposed to achieve uniform and effective cooling of the front and rear molds. However, the above methods are not completely effective when designing molds for products with complicated structures and high quality requirements. In order to solve this problem, conformal cooling technology came into being.
Conformal cooling means that the cooling water path changes as the geometry of the cavity surface changes. The emergence of built-in conformal cooling waterway mold manufacturing technology not only provides mold designers with a larger mold design space, but also simplifies the design method of cooling waterways.
It is well known that in a typical injection molding process, it takes a certain period of time for the mold to reach a stable production state, because when the molten plastic is injected into the mold, heat transfer between the injection mold and the molten plastic occurs at the contact surface, and The mold conducts heat pulse conduction to the cooling water passage by itself.
As a result, the mold temperature rises while transferring heat to the coolant. If the cooling water path is a long distance from the surface of the mold, a continuous heat pulse will continue to raise the temperature of the mold until the pulsed heat carried by the cooling system and the pulsed heat of the molten plastic to the mold are balanced. If the cooling water path is closer to the surface of the mold, the heat accumulated in the mold is greatly reduced, and the heat is confined to the area between the cooling water channel and the mold surface, so that the path for transferring heat from the surface of the mold cavity to the cooling water path is also shortened. a lot of. In this way, the mold can reach a stable working state in one injection cycle.