Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Silver streaks (also known as splay marks) are linear, silvery defects on molded plastic parts, often appearing as hazy or shiny lines. They are typically caused by moisture in the resin (which vaporizes during processing), material degradation from overheating, poor mold venting, or improper processing parameters. Preventing them involves addressing root causes like material preparation and machine settings.

Key Strategies to Avoid Silver Streaks

Here are proven steps to minimize or eliminate this defect, based on industry best practices:

1.Thoroughly Dry the Resin: Moisture is the most common culprit, as it turns to steam and etches the surface. Always pre-dry hygroscopic materials (e.g., nylon, ABS) using a dehumidifying dryer at the recommended temperature (typically 80–120°C for 2–6 hours). Measure moisture content to ensure it's below 0.02–0.05% before processing. Increase drying time if needed and verify dryer functionality.

2.Optimize Processing Temperatures:

Gradually increase barrel/melt temperature (e.g., by 10–20°C) to help evaporate residual moisture without degrading the material. Avoid overheating, which can cause off-gassing and worsen streaks.

Raise mold temperature slightly (5–10°C) to improve flow and reduce condensation.

For nozzle-specific issues, increase nozzle temperature to prevent premature freezing.

3.Adjust Injection Parameters:

Accelerate injection speed to reduce shear heating and moisture entrapment.

Increase hold (packing) pressure and time to ensure complete cavity filling without voids.

Shorten cycle time if possible to minimize heat buildup, but balance with cooling needs.

4.Improve Mold Design and Maintenance:

Enhance venting: Add or enlarge vent holes (0.01–0.03 mm deep) at the end of flow paths, or use vacuum venting to expel trapped gases.

Enlarge the cold slug well to capture early moisture or degraded material.

Ensure proper runner design to avoid dead spots where moisture can accumulate.

5.Select and Handle Materials Properly:

Choose resins with good fluidity to reduce shear-induced issues.

Store pellets in sealed, dry conditions to prevent reabsorption of humidity.

Purge the barrel regularly to remove contaminants or degraded resin.

6.Monitor and Troubleshoot Systematically:

Check for leaks in the feed throat or hopper that could introduce moisture.

Use adequate mold cooling to prevent surface defects from uneven contraction.

If streaks persist, test for material contamination or machine wear (e.g., worn screw/barrel).

Implementing these changes iteratively—starting with drying and temperatures—often resolves the issue quickly. For persistent problems, consult material suppliers for specific resin guidelines. If you're dealing with a particular material or setup, providing more details could help refine these recommendations.