The temperature control of hot runner systems
Hot runner thermocouple's position is the other key point for temperature control. There are two very critical position in the hot runner system.
One is the gate, where the temperatures are very important for mobility and continuous pressure melt; the other one is the point of maximum heat output.plastic here there is a risk of thermal decomposition.Therefore,the temperature of the thermocouple should be installed at the highest point of the expected never to be placed where heat loss occurs,such as a pressurized ring, near the seal ring, or outside the region hot runner body. At present,computer simulation can be carried out by the heat balance analysis, we can determine the basic nozzle, high temperature board split point.
Usually hot runner nozzle use external heating with spiral tubular heater sleeve outside the nozzle.There is also the choice of internal heating,heating rods inserted inside the nozzle. Heating manifold are generally used tubular heating rods,according to the shape of the curved manifold after the passage into the upper and lower surfaces of the plate.So we should pick up the best heater for each system.
Hot runner systems must be a state of thermal equilibrium, heat loss must be compensated by heating. Temperature control is extremely important, especially the gate and the nozzle portion of the hot runner mold which is extremely sensitive to changes in temperature, or even a few degrees change in temperature may lead to plastic failure.