Problem:
Evidence of a cold slug normally occurs close to a direct feed injection point, a small amount of melt solidifies at the gate point before the start of injection.

Solution:

1. Increase the temperature of the nozzle slightly.
2. Reduce the back pressure.
3. Increase the retraction of the screw - decompression.
4. Consider increasing the nozzle / gate diameter.
5. Consider use of a shut-off nozzle.
6. Reduce the time that the nozzle is in contact with the cold mould.

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Moldflow Consulting