How to solve the problem of surface depression?

Basic Reasons: From the perspective of plastics, when the plastics are cooled and contracted, insufficient feeding will lead to dents on the external surface or holes in the interior of the products.

Depression occurs in different locations, and the causes and solutions of the defects are also different.

1. When the depression occurs at the final cooling position of the thick-walled product or at a distance from the gate:
Cause analysis: Typical surface depressions or voids at the thick wall and far away from the gate are usually due to the increase of effective viscosity and pressure loss, resulting in insufficient cavity pressure, resulting in insufficient feeding pressure.
Solution: Increase the pressure of feeding and speed up the feeding rate

2. Surface depressions or cavitations occur near the gate
Cause analysis: Depression occurs near gate, usually due to lack of gate freezing.
There are several reasons affecting gate freezing: it may be caused by the decrease of effective viscosity; in most cases, the gate does not freeze due to the increase of plastic temperature; the die temperature is too high will also affect gate freezing.

Solution: By adjusting the mould temperature, plastic temperature and increasing the holding time to ensure the gate freezing.

3. Attention: Voids and bubbles are easily confused. Cavitations are sometimes misinterpreted as bubbles. Bubbles are trapped in gases and vacuums.



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