The temperature in the injection mold is uneven at each point and is also related to the time point in the injection cycle. The role of the mold temperature machine is to keep the temperature constant between 2 min and 2 max, which means that the temperature difference is prevented from fluctuating up and down in the production process or gap. The following control methods are suitable for controlling the temperature of the mold: controlling the fluid temperature is the most common method, and the control accuracy can meet most of the requirements. Using this control method, the temperature displayed in the controller and the mold temperature are not uniform; the temperature fluctuation of the mold is quite large, because the thermal factors affecting the mold are not directly measured and compensated for these factors including the injection cycle change, injection speed, melting temperature and Room temperature. The second is the direct control of the mold temperature. The method is to install a temperature sensor inside the mold, which is adopted when the mold temperature control accuracy requirement is relatively high. The main features of mold temperature control include: the temperature set by the controller is consistent with the mold temperature; the thermal factors affecting the mold can be directly measured and compensated. Typically, mold temperature stability is better than by controlling fluid temperature. In addition, mold temperature control is more reproducible in production process control. The third is joint control. Joint control is a combination of the above methods that simultaneously controls the temperature of the fluid and the mold. In joint control, the position of the temperature sensor in the mold is extremely important. When placing the temperature sensor, the shape, structure, and position of the cooling passage must be considered. In addition, the temperature sensor should be placed where the quality of the molded part is decisive. There are many ways to connect one or more mold temperature machines to the injection molding machine controller. It is best to use a digital interface from the standpoint of operability, reliability and immunity.