Mold-Masters Hot Runner - 20.6 Troubleshooting Typical Problems

20.6 Troubleshooting Typical Problems
20.6.1 Dark Specks
The nished product contains dark specks. Usually occurs when transparent
resins are used.
Probable Cause:
1. Molding Machine
• O󰀨-line for extended period
• Barrel o󰀨-line for extended period
• Barrel improperly purged
• Contamination in plasticizer
• Wrong nozzle
• Use of wrong screw
2. Mold
• Gate and / or runner has dead spots
3. Material
• Physical contamination of raw material
• Chemical contamination of raw material
• Particulate contamination from machine barrel
Solution (in sequence):
1. Purge system with appropriate material
2. Trace source of contamination and repair, remove or discard
3. Adjust melt temperature if necessary
4. Inspect for dead spots: gates, runners, nozzle, back ow valve
5. Inspect feed screw for degradation
20-5TROUBLESHOOTING
Hot Runner User Manual
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