The temperature of the mold has a profound impact on the injection molding process. Mold machines are employed to heat the molds and maintain their working temperatures, ensuring the stability of the quality of injection molded parts and optimizing the processing time. In the injection molding industry, the mold temperature plays a decisive role in both the quality of injection molded parts and the injection molding time. The temperature control system consists of three components: the mold, the mold temperature machine, and the heat conduction fluid.

1. Heat Balance of Injection Molds: Controlling the heat conduction of injection molding machines and molds is crucial for the production of injection molds.

Inside the mold, the heat brought by the plastic is transferred to the mold material and steel through thermal radiation and then conveyed to the heat conduction fluid by convection. Additionally, heat is dissipated to the atmosphere and the mold via thermal radiation. The heat absorbed by the heat fluid is removed by the mold temperature machine. The heat balance of the mold can be expressed as: P = Pm - Ps, where P represents the heat removed by the mold temperature machine, Pm is the heat introduced by plastics, and Ps is the heat emitted by the mold to the atmosphere.

2. Purpose of Controlling Mold Temperature and Its Influence on the Injection Molding Process:

The primary objective of controlling the mold temperature is to heat the mold to the working temperature and maintain it at a constant level. This enables the optimization of the cycle time and ensures the production of stable and high-quality injection parts. The mold temperature affects various aspects such as surface quality, fluidity, shrinkage, injection cycle, and deformation. For different materials, excessive or insufficient mold temperatures yield different effects. In the case of thermoplastics, a slightly elevated mold temperature generally enhances surface quality and fluidity but prolongs the cooling time and injection cycle. A lower mold temperature reduces shrinkage within the mold yet increases the shrinkage rate of the injection part after demolding. For thermoset plastics, a higher mold temperature typically reduces the cycle time, which is determined by the cooling time required for the part. Moreover, during plastic processing, a higher mold temperature also shortens the plasticizing time and decreases the number of cycles.

3. Preparation Conditions for Effective Control of Mold Temperature:

To ensure that heat can be added to or removed from the mold, all parts of the system must fulfill the following requirements. Firstly, inside the mold, the surface area of the cooling channel should be sufficiently large, and the diameter of the flow channel must be compatible with the pump capacity. The temperature distribution within the cavity significantly influences the deformation and internal pressure of the part. Reasonable design of cooling channels can mitigate internal pressure, thereby improving the quality of injection parts, shortening cycle times, and reducing product costs. Secondly, the mold temperature machine must be capable of maintaining the temperature of the heat conduction fluid within a range of 1 °C - 3 °C, depending on the quality requirements of the injection parts. Thirdly, the heat conducting fluid must possess excellent heat conductivity and, more importantly, be able to transfer a large amount of heat in a short time. From a thermodynamic perspective, water exhibits superior performance compared to oil.