How can dull spots be avoided behind sharp edges or in the gate area?

Possible cause:

• Cold slug that protrudes into the mold

Remedies:

• Check that nozzles are tight
• With mechanical shut-off nozzle, check that the latter functions properly- Increase nozzle temperature
• Raise mold temperature
• Avoid sharp edges, particularly at the transition from the gate to the mold cavity
• Round off and gates polish well
• Polish the nozzle, which should be conical to allow reliable extraction of the cold slug
• Provide a blind hole in front of the ejector
• Raise melt temperature

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