A small amount of melt solidifies at the gate point before the start of injection and is pushed into the mould cavity via the melt stream.
Evidence of a cold slug normally occurs close to the injection point.


1. Increase the temperature of the nozzle slightly.

2. Reduce the back pressure.

3. Increase the retraction of the screw – decompression.

4. Add a “cold slug well” to the cold runner feed system.

5. Consider increasing the nozzle / gate diameter.

6. Consider use of a shut-off nozzle.

7. Reduce the time that the nozzle is contact with the cold mould.