The design of injection mold cooling systems is often considered a secondary 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, and it will generate force for small plastic parts. For large plastic parts with thin walls, it will cause deformation and force cracking. Moreover, insufficient cooling results in an extended molding cycle, which reduces production efficiency.

   Next, in some simplified forms, the complex cooling process of the injection mold is studied, practical formulas are derived, and methods for determining the size of the cooling system are discussed based on these formulas.

   Determining the size of the cooling system is certainly not a simple task. In general, mold designers are still unfamiliar 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 problems. Some heat transfer equations are known, and computers and pocket programmable calculators can now be used to solve these equations. Despite this, the situation encountered in practical problems often brings difficulties to the solution of the problem. For example, the cavity walls are periodically heated by the injected high temperature plastic melt. As a result, the temperature difference between the mold and the cooling water is increased, 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. The solution to the problem becomes more difficult because the injected high temperature plastic melt only contacts a portion of the mold, the cavity, while the entire mold is cooled by the cooling water of the cooling passage. Further, the cooling water is heated while passing through the cooling passage of the mold, thereby changing the temperature difference between the mold and the cooling water.

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