Cold Slug

Cold Slug

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.

Solution: 

         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.