Sequential valve gate hot runner molding technology is widely used in large-sized automobile exterior parts, large household appliance shells and extra-large flat plastic parts, which can effectively eliminate weld lines, reduce internal product stress and improve overall forming quality. The stable operation of the whole sequential molding system relies on accurate zoning temperature control of the hot runner and real-time temperature feedback of matched high-precision thermocouples.
The core principle of sequential valve gate production is to control the opening and closing sequence and delay time of each group of nozzle valve needles according to the melt filling progress, so as to realize orderly feeding and sequential filling of different positions. In this process, independent temperature control zones must be divided for each sequential nozzle, and each nozzle is equipped with exclusive special thermocouples to independently monitor and adjust the gate local temperature. According to the filling distance and melt flow speed demand of different positions, differentiated temperature values are set to balance the melt fluidity of each feeding port.
For the early opening feeding nozzles, appropriately lower the gate temperature to slow down the melt flow speed and avoid excessive melt accumulation in the front section; for the delayed opening rear nozzles, properly increase the set temperature to ensure that the melt maintains good fluidity after delayed start-up and smoothly connects with the front melt flow front. Accurate temperature data provided by thermocouples can help technicians quickly optimize the temperature difference matching scheme of each group of valve gates, making the whole filling process smooth and orderly.
Stable manifold overall constant temperature is the basic guarantee for sequential molding. The main flow channel manifold maintains a stable overall temperature through multi-point distributed thermocouples to ensure that the temperature of the melt delivered to each branch nozzle is uniform and stable, avoiding fundamental fluidity difference caused by manifold temperature imbalance. On this basis, fine-tune the local temperature of each nozzle gate to realize perfect coordination of overall temperature stability and local temperature difference adjustment.
Reasonable temperature matching can also effectively reduce the failure rate of sequential valve needle actions. Stable and appropriate gate temperature can prevent valve needle jamming caused by melt solidification or excessive viscosity, ensure flexible and accurate opening and closing actions of each group of valve needles according to the set program. In daily production debugging, technicians can quickly optimize the sequential delay time and temperature matching parameters by relying on real-time temperature data of thermocouples, greatly shorten the mold trial optimization cycle, effectively eliminate obvious weld lines on large parts, improve product surface flatness and dimensional stability, and greatly improve the yield of large complex injection molded parts.
