1, the heat balance of injection mold controls the heat conduction between injection molding machine and mold, which is the key to produce injection molded parts. Inside the mold, the heat brought by plastics (such as thermoplastics) is transferred to the material and steel of the mold by thermal radiation, and to the heat-conducting fluid by convection. In addition, heat is transferred to the atmosphere and the mold matrix by thermal radiation. The heat absorbed by the heat conducting fluid is taken away by the mold temperature machine.

2. The purpose of controlling mold temperature and the influence of mold temperature on injection molded parts. In the process of injection molding, the main purpose of controlling the mold temperature is to heat the mold to the working temperature, and the other is to keep the mold temperature at the working temperature. If the above two points are successful, the cycle time can be optimized, thus ensuring the stability and high quality of injection molded parts. Mold temperature will affect surface quality, fluidity, shrinkage, injection cycle and deformation.

Too high or insufficient mold temperature will have different effects on different materials. For thermoplastics, higher mold temperature usually improves surface quality and fluidity, but prolongs cooling time and injection cycle. Lower mold temperature will reduce the shrinkage in the mold, but it will increase the shrinkage rate of injection molded parts after demoulding. For thermosetting plastics, higher mold temperature usually shortens the cycle time, which is determined by the time required to cool the parts. In addition, in plastic processing, higher mold temperature will also reduce plasticizing time and cycle times.

3. Preparation conditions for effective control of mold temperature The temperature control system consists of mold, mold temperature machine and heat conducting fluid. In order to ensure that heat can be added to or removed from the mold, all components of the system must meet the following conditions: First, the surface area of the cooling channel must be large enough inside the mold, and the diameter of the channel should match the capacity (pressure) of the pump. The temperature distribution in the cavity has great influence on the deformation and internal pressure of the parts. Reasonable setting of cooling channels can reduce internal pressure, thus improving the quality of injection molded parts.

It can also shorten the cycle time and reduce the product cost. Secondly, the mold temperature machine must be able to keep the temperature of the heat-conducting fluid constant within the range of 1℃-3℃, depending on the quality requirements of injection molded parts. Thirdly, the heat-conducting fluid must have good heat-conducting ability, and most importantly, it must be able to introduce or output a lot of heat in a short time. From a thermodynamic point of view, water is obviously better than oil.