- molds and plastics  injection troubleshooter -



• Discoloration - plastic injection troubleshooter


• Description:

The appearance of areas in the moulding with a deviating colour.


• Causes:
machine · contamination
mould · check sprue diameter
· pin-point too small
· poor venting
material · melt too hot or too low, may create shear
· long residence time
· instability of polymer / pigments


• Actions:

1st. purge heating cylinder
2nd. lower material temperature by
- reducing cylinder temperature
- decreasing screw speed
- reducing back pressure
3rd. lower nozzle temperature
4th. check residence time
5th check machinery purging
6th shorten overall cycle
7th check hopper and feed zone for contaminants
8th check for proper cooling of ram and feed zone
9th provide additional vents in mould
10th move mould to smaller shot size press to reduce residence time


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