As is well known, injection molding is an important method for producing plastic products. Molten plastic is injected into plastic product molds under pressure and cooled to form various desired plastic parts. Injection molding is an industry with a wide range of knowledge, strong technical and practical aspects. Therefore, when conducting injection molding, we must be more rigorous to avoid affecting the effectiveness of injection molding.

During the injection molding process, there are often two types of pressures that can affect the plasticization of plastic and the quality of the product. One is the plasticization pressure, and the other is the injection pressure. Poor control of these two pressures can directly affect the plasticization of plastic and the quality of the product.

Plasticizing pressure: When using a screw injection machine, the pressure exerted by the molten material at the top of the screw when it rotates and retreats is called plasticizing pressure, also known as back pressure. The magnitude of this pressure can be adjusted through the overflow valve in the hydraulic system. In injection, the size of the plasticizing pressure needs to be changed according to the design of the screw, the requirements for product quality, and the type of plastic. If these conditions and the rotational speed of the screw remain unchanged, increasing the plasticizing pressure will strengthen the shear effect, which will increase the temperature of the melt, but will reduce the efficiency of plasticizing, increase countercurrent and leakage flow, and increase driving power.

In addition, increasing the plasticizing pressure often results in a uniform temperature of the melt, a uniform mixing of pigments, and the discharge of gases from the melt. In general operations, the determination of plasticizing pressure should be as low as possible while ensuring good product quality. The specific value varies depending on the type of plastic used, but usually rarely exceeds 20 kilograms per square centimeter.

Injection pressure: In current production, the injection pressure of almost all injection machines is based on the pressure applied to the plastic at the top of the plunger or screw (converted from oil pressure). The role of injection pressure in injection molding is to overcome the flow resistance of plastic from the barrel to the cavity, provide the rate of mold filling for the molten material, and compact the molten material.