20.6.8 Flash
Also known as “ns” or “spew”. The nished product contains a thin lm of
material attached at the mold parting line.
Probable Cause:
1. Molding Machine
• Low clamping pressure
• High injection pressure
• High injection speed
2. Mold
• Inadequate mold supports
• Low clamping force
• Damaged mold
• Projected area too large for machine capacity
3. Material
• Low melt viscosity
• High melt temperature
Solution (in sequence):
1. Reduce the injection speed
2. Reduce the injection pressure
3. Reduce the injection time
4. Increase clamping force
5. Inspect the mold for irregularities
6. Reduce the melt temperature
7. Inspect vent depth
8. Switch to higher tonnage clamping machine
9. Establish correct transfer position
10. Reduce hold pressure
20-12
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