Cause of damage of syringe mold

The design of the injection mold cooling system 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 not suitable for the mold principle of the syringe. For small plastic parts, internal stress will be generated, while for large plastic parts with thin walls, deformation or even stress cracking will be caused. Moreover, insufficient cooling will lead to prolonged molding cycle, thus reducing production efficiency.

In the following, the complex cooling process of the injection mold is studied in some simplified forms, and the practical formulas are derived. Based on these formulas, the methods for determining the size of the cooling system are discussed. Determining the size of the cooling system is no doubt not an easy task, and in general, the die designer is not familiar with some aspects. This kind of work is complex, and even in the technical literature it is difficult to find a satisfactory answer to certain questions. Some of the heat transfer equations are well known and can now be solved using computers and pocket programmable calculators.

However, the situation encountered in the actual problem often brings difficulties to the solution of the problem. For example, the cavity walls are periodically heated by the injection of a 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 piece is ejected, the cavity is cooled by the surrounding air. Therefore, the temperature on the surface of the cavity changes periodically. Solving the problem was made more difficult by the fact that the injection of high-temperature plastic melt was in contact with only part of the mold cavity, while the entire mold was cooled by the cooling water in the cooling channel. In addition, the cooling water is heated as it passes through the mold's cooling channels, which changes the temperature difference between the mold and the cooling water.