20.6.16 Splay
The nished product display splay / splash marks and / or silver streaks.
Probable Cause:
1. Molding Machine
• Resin degraded from overheating
• Cylinder contains hot spots
• Material trapped at nozzle tip
• Wrong injection pressure
• Wrong injection speed
• Low back pressure
2. Mold
• Friction related burning in gate, nozzle or Hot Runner
• Trapped volatile compounds
3. Material
• Hot melt
• Contaminated resin (moisture, dirt, organics)
• Degraded resin
Solution (in sequence):
1. Dry resin according to procedure; check drying equipment for
functionality
2. Reduce nozzle temperature
3. Reduce material temperature:
• lower cylinder temperature
• reduce screw speed
• reduce back pressure
4. Decrease injection speed
5. Increase mold temperature
6. Decrease or eliminate screw decompression
7. Reduce cycle time
8. Check for drooling
9. Check for contamination in mold cavity
10. Open gates
11. Try mold in smaller shot-size press
20-20
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