Mainly talks about the pressure control of injection molding processing
As is known to all, injection molding processing is an important method in the production of plastic products, the use of the molten plastic into the plastic mould, injection pressure cooling molding get all kinds of plastic parts. Injection molding processing is a broad scope, technical and practical industry, so we in the injection molding processing, must be careful, lest affect the effect of injection molding processing.
In the process of the injection molding processing, tend to be influenced by two kinds of pressure, pressure is a kind of plasticizing, another is the injection pressure, the two pressure control is not good, can directly affect the quality of plasticizing and plastic products.
Plasticizing pressure: using screw injection machine, screw at the top of the molten material in the screw rotating back pressure is called the plasticizing, which is also called back pressure. The size of the pressure can be found on the overflow valve to adjust the hydraulic system. In injection, the size of the plasticizing pressure is depending upon the design of the screw, the product quality requirements, and the type of plastic and needs to change, if the situation and the screw rotation speed is constant, increase plasticizing pressure will strengthen shearing action, which will raise the temperature of the melt, but will reduce the plasticizing efficiency, increase the current and leakage flow, increase the driving power.
In addition, increase plasticizing pressure often can make the melt temperature uniformity, color mixing and discharge gas in the melt. The decision of the general operation, the plasticizing pressure should be on the premise of guarantee the products quality is lower, the better, the specific values are vary with the varieties of the plastic, but usually rarely more than 20 kg/cm2.
Injection pressure: in the current production, almost all the injection pressure of injection machine are in plunger or it can be applied to plastic screw top pressure (by oil pressure conversion) shall prevail. Injection pressure in injection molding, the role of is, to overcome the flow resistance of plastic flowing from cylinder cavity, given the rate of molten material molding and compaction of molten material.