The design of a syringe mold cooling system is often considered a minor issue. Not enough attention has been paid to the size and structural design of the cooling system. The design of the cooling system is unreasonable, it will cause internal stress for small plastic parts, and it will cause deformation and even stress cracking for large plastic parts with thin walls. Moreover, insufficient cooling can lead to prolonged molding cycles, which reduces production efficiency.
In the following, some simplified forms are used to study the complex cooling process of injection molds, practical formulas are derived, and the methods for determining the size of the cooling system are discussed based on these formulas.
Determining the size of a cooling system is undoubtedly not a simple task. Generally speaking, mold designers are not familiar with certain aspects. This kind of work is very complicated, and even in the technical literature, it is difficult to find a satisfactory answer to some questions. Some heat conduction equations are known, and these equations can now be solved using computers and pocket programmable calculators.
Nevertheless, the situations encountered in actual problems often bring difficulties to the solution of the problems. For example, the cavity wall is periodically heated by the injected high-temperature plastic melt. As a result, the temperature difference between the mold and the cooling water increases, and the cooling effect becomes stronger. After the mold is opened and the plastic part is ejected, the cavity is cooled by the surrounding air. Therefore, the temperature of the cavity surface changes periodically. Solving the problem becomes more difficult, because the injected high-temperature plastic melt only contacts a part of the mold, the cavity, and the entire mold is cooled by the cooling water of the cooling channel. In addition, the cooling water is heated as it passes through the cooling channels of the mold, thereby changing the temperature difference between the mold and the cooling water.