In the process of plastic injection parts, the magnitude of injection pressure affects the molding. The pressure in the plastic injection parts process includes plasticizing pressure and injection pressure, which directly affect the plasticizing of plastics and the quality of products.

　　1. Plasticizing pressure: When a screw injection machine is used, the pressure generated by the melt at the top of the screw when the screw rotates backward is the plasticizing pressure. Plasticizing pressure can be determined by adjusting the relief valve in the hydraulic system. In injection, the magnitude of plasticizing pressure is different due to the requirements of plastic injection parts and the types of plastics. If the rotating speed of the screw is constant, the shearing effect after the plasticizing pressure increases will be strengthened, the temperature of the melt will increase, the plasticizing strength will decrease, the counterflow and leakage flow will increase, and the driving power will increase. Plasticizing pressure affects the temperature uniformity of melt, the mixing uniformity of pigment and the size of gas discharged from a melt. In general operation, the plasticizing pressure should be as low as possible on the premise of ensuring good product quality, and the value will vary depending on the type of plastic used, but usually, it rarely exceeds 20 kg/cm2.

　　2. Injection Pressure: In the current production, the injection pressure on most injection machines is subject to the pressure exerted on plastic by the top of the plunger or screw. The injection pressure can reduce the flow resistance of plastic from the charging barrel of the cavity, push the filling rate of molten material and increase the pressure on molten material.

　　plastic injection parts in order to ensure the quality of plastic injection parts, pay attention to the pressure control method in the process of plastic injection parts. According to the required quality of the product, select the appropriate pressure control mode and pressure magnitude.