Oct 9, 2026Material Guides
PC/ABS Molding Defects: How to Prevent Silver Streaks, Warpage and Poor Surface Finish
Solve common PC/ABS injection molding defects, including silver streaks, warpage and poor surface finish. Use this practical resin and process checklist.
PC/ABS is widely evaluated for electronic housings, appliance parts, automotive interiors and other injection molded components because it can balance toughness, heat resistance, flow and surface appearance.
But when a part shows silver streaks, warpage, flow marks or inconsistent gloss, changing the resin grade is not always the right first response.
This troubleshooting guide helps processors review the most common causes before making a costly material or tooling change.
1. Silver Streaks and Splay Marks
Silver streaks usually appear as visible lines or streaks on the molded surface. They can create cosmetic rejects even when the part’s dimensions remain acceptable.
Common areas to check include:
- Resin moisture condition before processing
- Drying method and dryer performance
- Hopper exposure time
- Regrind control
- Contamination in the feed system
- Excessive shear or unsuitable barrel-temperature settings
Start with the specific grade’s current TDS. Do not copy drying conditions from a different PC/ABS grade without confirming that the recommendation applies.
2. Warpage and Dimensional Instability
Warpage often results from uneven shrinkage, part geometry or unbalanced cooling—not from one single cause.
Review:
- Wall-thickness variation
- Gate position and flow direction
- Mold-temperature consistency
- Cooling time
- Packing pressure and holding time
- Fibre, filler or regrind content where applicable
- Grade-specific shrinkage information
A resin change may help in some cases, but mold design and processing stability should be checked first.
3. Poor Surface Gloss or Flow Marks
For visible housings, surface quality is often a purchasing requirement, not simply a production preference.
Poor gloss or flow marks may be connected to:
- Mold-surface condition
- Melt temperature outside the recommended window
- Mold temperature that is too low or inconsistent
- Incomplete venting
- Long flow paths
- Moisture or contamination
- A grade mismatch between the material and the appearance requirement
Before ordering resin, share a photo or sample of the required finish with the supplier. “Natural black PC/ABS” or “general-purpose PC/ABS” alone may not define the correct grade.
4. Brittle Parts or Low Impact Performance
If the finished part becomes brittle, inspect the complete process history.
Potential contributors include:
- Excessive residence time
- Material degradation caused by unsuitable processing conditions
- Incorrect use of regrind
- Storage or handling issues
- Grade selection that does not match the impact requirement
- Test-method differences between supplier data and your own test
Do not compare impact values without checking specimen thickness, conditioning and test standard.
5. Colour Variation Between Batches
Colour variation can affect both black housings and custom-coloured consumer products.
To reduce disputes, agree before shipment on:
- Approved colour standard or master sample
- Batch traceability
- Inspection method
- Acceptable colour tolerance
- Packaging and storage requirements
- Whether a colour-matching approval is needed before bulk production
A Pre-Order Checklist for PC/ABS Buyers
Before confirming an order, request:
- Current TDS, COA and SDS
- Exact grade name and manufacturer identification
- Processing guidance for the proposed grade
- Colour and appearance specification
- Flame-retardancy documentation where required
- Packaging details and batch traceability
- A sample for production testing
Final Takeaway
Most PC/ABS molding defects are not solved by changing resin blindly. Start with moisture control, process stability, tooling conditions and the exact grade specification. Then use a documented trial to determine whether a resin adjustment is necessary.
Request PC/ABS Technical Support
Lema Plastic can help buyers compare PC/ABS grades for electronic housings, appliance components, automotive interior parts and molded consumer products. Send your defect description, current grade, process information and target application for a practical review.
