What is the role of pressure control in the injection molding process?

Author: MULAN - Plastic Molding Manufacturer

During the mold injection molding process, the pressure control during the injection cycle: the actual applied pressure needs to be higher than the pressure of the filling cavity. During the injection process, the mold control pressure rises sharply and finally reaches a peak value. This peak is often referred to as injection pressure.

The injection pressure is significantly higher than the pressure of the filling cavity. Why hold pressure? The effect of this is as follows: ① After filling the cavity with plastic until the gate is completely cooled for a period of time before closing, the plastic in the cavity still needs a relatively high pressure support, that is, holding pressure. ② Supplement the amount of material near the gate, and prevent the unhardened plastic in the cavity from flowing back to the gate material source under the action of residual pressure before the gate condenses.

③Prevent shrinkage of parts and reduce vacuum bubbles. Reduce sticky mold cracking 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 pressure is maintained or the time is too long, the gate may be blocked, and the cold material on the runner is squeezed into pieces, so that the bright spot of the cold material increases to a position near the gate, thereby prolonging the cycle without any benefit. Generally, how to choose the injection pressure in the actual injection mold processing: ①Select according to the shape of the workpiece. ② Choose different plastic materials.

When the production conditions and quality standards of the parts allow, it is recommended to use low temperature and low pressure process conditions.