How do you set the process for injection molding?

The program control of the injection speed is to divide the injection stroke of the screw into 3~4 stages, and use the appropriate injection speed respectively in each stage.
For example: at the beginning of the molten plastic through the gate to slow down the injection speed, in the process of filling the mold using high-speed injection, in the end of the filling mold to slow down the speed. In this way, the overflow can be prevented, the flow trace can be eliminated and the residual stress of the product can be reduced.
At low speed, the flow rate is stable, the size of the product is relatively stable, the fluctuation is small, the internal stress of the product is low, the internal and external stress of the product tends to be consistent (for example, a polycarbonate parts dipped in carbon tetrachloride, with high-speed injection molding parts have a tendency to crack, low speed does not crack).
Under the condition of slow mold filling, the temperature difference of material flow, especially before and after sprue, is large, which is helpful to avoid the occurrence of shrinkage cavity and depression. However, due to the long duration of filling time, it is easy to make the parts appear layered and bad combination of weld marks, which not only affects the appearance, but also greatly reduces the mechanical strength.
When the high-speed injection, the material flow speed is fast, when the high-speed mold filling is smooth, the molten material quickly fills the cavity, the material temperature drops less, the viscosity drops less, can use lower injection pressure, is a hot material filling situation. High speed filling can improve the glossiness and smoothness of the workpiece, eliminate the phenomenon of seam line and layering, small shrinkage depression, uniform color, the workpiece more than most can ensure fullness.
But easy to produce products fat blister or parts yellow, or even burn zoom, or cause mold removal difficulties, or the phenomenon of uneven mold filling. For high viscosity plastics may lead to melt rupture, so that the surface of the parts produced by fog spots.