Black Specks, Flow Marks and Color Streaks: A Plastic Resin Troubleshooting Checklist
Troubleshoot black specks, flow marks and color streaks in molded plastic parts. Use this buyer and processor checklist before changing resin grades or suppliers.
1. Black Specks: Check for Contamination and Degradation
- Contamination in resin handling or conveying equipment
- Material left in the barrel or dead spots in the melt path
- Degraded residue from a previous production run
- Contamination from regrind
- Foreign pellets, dust or packaging debris
- Excessive residence time or unsuitable processing conditions
2. Flow Marks: Review the Full Process, Not Just the Resin
- Gate location and flow length
- Mold-surface condition
- Melt and mold temperatures
- Injection speed and holding pressure
- Wall-thickness changes
- Venting condition
- Moisture control
3. Color Streaks: Trace Every Material Input
- Masterbatch ratio and feeding accuracy
- Mixing consistency
- Colour-change cleaning procedure
- Regrind separation
- Hopper and conveyor cleanliness
- Storage conditions
- Batch-to-batch colour standard
4. Compare the COA With the Actual Production Batch
- Resin grade and batch number
- Current COA
- Production date
- Packaging condition on arrival
- Photos of the resin before processing
- Drying record
- Processing settings
- Defect photos and defect rate
- Retained samples from both good and defective production
5. Review Storage and Handling Conditions
- Bags remain sealed until use
- Opened material is identified and protected
- Conveying lines are cleaned between grades
- Regrind is separated and controlled
- Feed hoppers and dryers are maintained
- Warehouse handling prevents bag damage and contamination