What should we pay attention to when using the PVC injection molding machine?

PVC raw materials are sensitive to impurities and should not be mixed with other plastics during the production process. Clean the barrel and screw before injection molding. Especially when changing raw materials, PE or PP materials should be used as cleaning agents to prevent impurities from remaining. If the PVC raw materials are stored for more than 6 months or in a high temperature and humid environment, they should be dried at 60-80℃ to remove excess moisture and avoid bubbles during the molding process.

The screw design of the PVC injection molding machine is particularly critical. When using it, a gradient screw with a length-to-diameter ratio of 20:1 and a compression ratio of 1:1.6-1:1.2 is recommended. This design can balance plasticizing efficiency and thermal stability and reduce material retention time. Temperature control needs to be adjusted in stages. The temperature at the front end of the barrel is controlled at 160-180℃, and the rear end is maintained at 190-200℃ to avoid local overheating and PVC decomposition. The injection speed needs to be controlled in multiple stages, starting slowly in the initial stage and gradually accelerating as the mold is filled to prevent shear heat from causing coking. At the same time, back pressure control is required to avoid material degradation due to excessive shear force.

Before starting the PVC injection molding machine, the hydraulic system, electrical circuits and cooling water circuits need to be fully checked to ensure that there is no leakage or blockage, especially to verify whether the safety door switch and emergency stop function are sensitive. During the injection process, the melt temperature fluctuation needs to be monitored regularly (within ±2°C), and the decomposition gas should be discharged in time through the vacuum exhaust system to prevent equipment corrosion and product defects. The mold design needs to avoid sharp corners, the runner adopts a circular cross-section to reduce flow resistance, and the mold temperature is controlled at 30-60°C to balance the cooling rate and molding accuracy.