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1.The actual applied pressure should be higher than the pressure of the filled cavity. During the injection process of the injection molding process, the pressure controlled by the injection mold rises sharply and finally reaches a peak. This peak is usually called the injection pressure, and the injection pressure is significantly higher than the pressure of the filled cavity.
2. The role of injection molding equipment to maintain pressure: After filling the cavity with plastic until the gate is completely cooled, the plastic in the cavity still needs a relatively high pressure support, that is, pressure maintenance. Its specific function is to supplement the amount of material near the gate and prevent the unhardened plastic in the cavity from flowing back to the source of the gate material under the action of residual pressure before the gate condenses. Prevent parts from shrinking and reduce vacuum bubbles; reduce the phenomenon of sticky mold rupture or bending deformation caused by excessive injection pressure of parts. Therefore, the holding pressure is usually 50% to 60% of the injection pressure. If the holding pressure or time is too long, it is possible to squeeze the cold material on the gate and runner into a sheet, thereby increasing the bright spot of the cold material near the gate and prolonging the cycle time. In the sun, streaks may appear in the product. The problem needs to be considered from two aspects of the physical and mechanical properties of the plastic and the plastic molding process: the temperature control of the injection molding equipment is poor, and the masterbatch cannot be fully mixed with the resin after entering the mixing chamber. The injection molding machine does not increase a certain amount of back pressure, and the screw mixing effect is not good. The dispersion of the color masterbatch is not good or the plasticization of the resin is not good.