Auto Parts Injection Molding

Back pressure refers to the pressure that the screw needs to overcome when the screw is reversed and withdrawn to store the material. The use of high back pressure is conducive to the dispersion of the pigment and the melting of the plastic, but at the same time, it prolongs the retraction time of the screw, reduces the length of the plastic fiber, and increases the pressure of the injection molding machine. Therefore, the back pressure should be lower, generally not more than the injection molding machine. 20% of the pressure. When injection molding foam, the back pressure should be higher than the pressure created by the gas, otherwise the screw will be pushed out of the barrel. Some injection molding machines can program back pressure to compensate for the reduction in screw length during melting, which reduces heat input and reduces temperature. However, because the results of such changes are difficult to estimate, it is not easy to make corresponding adjustments to the machine.