Mold-Masters Hot Runner - Weld Lines

20.6.20 Weld Lines
The nished product has lines where two ow fronts meet and have not
fused, creating the possibility of weak areas and stress fractures.
Probable Cause:
1. Molding Machine
• Low injection speed
• Low injection pressure
• Short injection time forward
2. Mold
• Low mold temperature
• Poor venting
• Back ow valve / check ring malfunctioning
• Gates too far apart
• Redesign part
3. Material
• Cold melt
• Material wrong grade for application
Solution (in sequence):
1. Increase injection pressure
2. Increase injection holding time
3. Increase injection speed
4. Increase cylinder temperature
5. Increase mold temperature
6. Check for venting
7. Provide an overow well adjacent to the weld area
8. Modify the gate location
9. Decrease gate land length
20-24
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