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Brief Discussion On Temperature Control Of Hot Runner System
May 23, 2017

Brief discussion on temperature control of hot runner system
Hot runner system must be a thermal equilibrium state, heat loss must be compensated by heating. The temperature control of the hot runner system is extremely important, especially the gate and nozzle parts of the hot runner mold are extremely sensitive to the temperature change, even several degrees of temperature change may result in plastic products unqualified. Therefore, accurate temperature control is very important for a hot runner system which has good function and can be operated automatically. The current temperature controller mostly adopts PIDD structure, which can control the temperature change within 1 Shan.

The arrangement of hot runner thermocouple is another key point of temperature control. There are two very critical places in the hot runner. One is the gate, where the temperature is important for the fluidity and constant pressure of the melt; the other is the biggest point of heat output, where the plastic is in danger of thermal decomposition. Therefore, thermocouples should be installed at the highest expected temperature, in no place where heat loss occurs, such as the pressure ring, near the seal ring, or the outer area of the hot runner body. At present, the thermal equilibrium can be analyzed by computer simulation, which can be used to determine the high temperature point on the nozzle and the shunt board.

Hot runner nozzles are generally heated by external heating methods, with spiral tubular heaters outside the nozzle. Also has the choice internal heating way, uses the heating stick to insert inside the nozzle. The heating of the runner plate is usually tubular heating rod, and the upper and lower two surfaces of the inflow path plate are bent according to the shape of the runner plate.