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Pressure control during the injection cycle

Update:11 May 2018
Summary:

The actual pressure applied should be higher than the f […]

The actual pressure applied should be higher than the full cavity pressure. During the injection process, the mold pressure rises sharply and eventually reaches a peak. This peak is the so-called injection pressure. The injection pressure is obviously higher than the full cavity pressure.

The role of pressure holding pressure: After the cavity is filled with plastic until the gate is completely cooled and closed for a period of time, the plastic in the cavity still needs a relatively high pressure support, that is, maintaining pressure, and its specific role is:

The quantity of material near the gate is supplemented, and before the gate condensation closes, the uncured plastic in the mold cavity is controlled to flow back toward the gate material source under residual pressure.

Prevent shrinkage of parts and reduce vacuum bubbles.

Reduce the phenomenon of sticking or bending deformation caused by excessive injection pressure of the parts. Therefore, the holding pressure is usually 50%~60% of the injection pressure. The pressure of the holding pressure or the time is too long, the gate may be too large. The cold material on the flow path slams into the part, adding bright spots near the gate and prolonging the cycle without any benefit.

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