The cooling stage in plastic injection molding is an indispensable and important stage for injection molding products. How should we properly handle the cooling process? What are the common problems during cooling

The cooling process of injection molded parts in the mold refers to the whole process of releasing injection molded parts from the mold core when the plastic solution at the gate is completely frozen. At this stage, feeding or countercurrent will not continue, and the plastic in the mold cavity will continue to cool, harden and solidify

When the plastic injection molding is customized for demoulding, the plastic injection molding parts have sufficient rigidity, and will not produce shrinkage and deformation. As the cooling process continues, the temperature continues to decrease, the plastic in the mold cavity shrinks, and the pressure decreases. When demoulding, the pressure in the mold cavity drops to a low point, but not necessarily equal to the external atmospheric pressure. The difference between the pressure in the mold cavity and the external atmospheric pressure becomes the residual pressure, and the residual pressure is related to the length of the pressure holding stage of the injection molded part. When the residual pressure is exactly the same, it is difficult to exit the mold, and the injection parts are easy to be scratched or broken. When the residual pressure is negative, the surface of the injection molded part has defects or there are vacuum bubbles inside. Therefore, only when the residual pressure is close to zero, can the injection molded part be more convenient and satisfactory

The cooling rate of plastic parts shall be moderate. If the cooling speed is too fast, or the temperature of the parts in contact with the mold core and plastic solution is different, it will cause uneven cooling and inconsistent shrinkage, which will lead to thermal stress and warpage of the plastic injection molding process