How can bubbles be avoided inside a thick-walled molding?

This fault points to various causes:

• Mold not optimally filled
• Shrinkage not adequately compensated for
• Air entrapment (fluctuations in material feed)

Remedies:

• Examine material feed
• Reduce melt temperature
• Extend hold time
• Increase holding pressure
• Reduce injection speed
• Increase mold temperature
• Reduce screw speed
• Raise back pressure
• Improve predrying
• Enlarge gates and possibly runners

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