How can black streaks and dark clouding and / or milky bubbles be avoided?
This faults point to various possible causes:
1. Air intake, fluctuations in material feed
Remedy:
- Increase back pressure
- Vary feed temperature
- Cool water in feed section
- Clean cylinder
- Avoid contamination (other thermoplastics)
- Add lubricant to the surface of the pellets
2. Fluctuations in material feed due to brief or prolonged interruptions of cycle (screw becomes too hot)
Remedy:
- Avoid interruption
- Always retract screw when machine is not in operation
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