There are three ways of heat transfer: radiation, convection and conduction. In the mold, the heat generated by the plastic brought into the mold is 95% absorbed by the mold through conduction, and about 5% is emitted into the air by radiation and convection. During the processing, the temperature change is the most important influencing factor, and it has a great impact on the quality of the finished product, and indirectly affects the production efficiency.
The mold temperature control method is to cool the mold with a liquid flowing in the cooling pipe. Since water is quite cheap, water is used as the primary coolant to cool the mold. The water can shorten the rapid cooling time by guiding the mold. Usually colder molds are more effective because of faster production cycle times. However, this is not necessarily correct, because some materials are too cold and have the opposite effect.
Beryllium copper inserts are usually used in the mold to improve the cooling effect of the mold. The parts of the mold that are not good for heat dissipation (such as the part wrapped around the plastic parts) can also quickly transfer heat to the cooling water flowing through it through the beryllium copper material with good thermal conductivity, so as to achieve the cooling effect.
There are also plastics with high melting temperature that require the mold to be heated for injection molding. For example, a resistance wire heating rod is used to inlay the mold base to heat the mold.
The liquid used for mold cooling is water and oil; usually, there are three common types: water, ice water, and water plus antifreeze.
Conversely, when the mold temperature needs to be increased, hot water is used to heat the mold.
The thermal equilibrium control of the injection mold is one of the keys to determining the quality of the injection molded parts. How to choose and control must deeply integrate the structure, performance, function, requirements, etc. of the product to ensure the quality while controlling the cost to the lowest.