During the injection molding process of plastic varieties, due to the volume changes caused by crystallization, the pressure during injection molding is high, the viscosity difference of the molten material is small, the interlayer shear stress is small, and the elastic rebound after demolding is large. Therefore, the shrinkage during injection molding can also be moderately reduced. During injection molding, the material temperature is high and the shrinkage is large, but its directionality is small.

When the pressure increases during pressure injection molding, the molten material is subjected to greater shear, and the fluidity will also increase. Especially, PE and POM are more sensitive, so the pressure during injection molding should be adjusted to control the fluidity. During molding, factors such as material temperature, mold temperature, pressure during injection molding, and injection speed can also be controlled to appropriately adjust the filling situation to meet molding needs.