There are three ways of heat transfer: radiation, convection, and conduction. The heat generated when the plastic enters the mold is absorbed by the mold through conduction, and about 5% of the heat is dissipated into the air through radiation and convection. In the automotive plastic part manufacturer's injection mold processing process, temperature changes are the most important factor, which has a great impact on the quality of finished products and indirectly affects production efficiency.
The mold temperature control mode of automotive plastic part manufacturers is to cool the mold with liquid flowing in the cooling pipe. Because water is very cheap, water is used as the main coolant to cool the mold, which can shorten the rapid cooling time by guiding the mold. Generally, it is more effective than cold mold because it can have a faster production cycle. However, this is not necessarily true, because some materials are too cold, which has the opposite effect.
Beryllium copper inserts are usually used in molds to improve the cooling effect of injection molds. The mold can quickly transfer heat to the cooling water flowing through the beryllium copper material with good thermal conductivity and take it away to achieve the cooling effect.
There are also high-melting plastics that need to be heated and injected into the mold. For example, resistance wire heating rods are embedded in the mold blank to heat the mold. Liquid, water, and oil are used for plastic mold cooling; usually, water, ice water, and water plus antifreeze are used. Conversely, when the mold temperature needs to increase, hot water is used to heat the mold.
The large temperature difference also indicates that the design of the cooling water circuit is not ideal. The pressure loss of the cooling water circuit in the mold can also be obtained by measuring the pressure difference between the water circuit and the inlet and outlet, and it can be judged whether the water circuit design is reasonable.
The thermal balance control of the injection molds of automotive plastic part manufacturers is one of the keys to determining the quality of injection molded products. How to choose and control should be closely integrated with the structure, performance, function, and requirements of the product to ensure quality and reduce costs.