How can a chipped surface and striation be avoided in moldings?

This fault points to various causes:

1. Material is too damp

Remedies:

• Predry material
• Lower melt temperature
• Raise injection pressure
• Increase injection speed
• Increase back pressure

2. Decomposition due to overheating of melt

Remedies:

• Check melt temperature (cylinder nozzle and hot runner) and reduce if necessary
• Lower back pressure
• Reduce screw speed
• Reduce injection speed
• Enlarge gates and possibly runners

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