Product Info

Injection molding defects like flow marks, voids, and warping can severely impact part quality and production efficiency. Learn the root causes and proven solutions for common molding issues—plus how to prevent them with better design and machine control.

1. Flow Marks
Appearance: Wavy lines or streaks along the plastic flow direction
Causes:
- Low injection speed
- Inadequate mold or resin temperature
- Poor runner/gate design

Solutions:
- Increase injection speed
- Raise mold or melt temperature
- Redesign flow path (gate and runner) for smoother filling

2. Air Traps & Voids
Appearance: Internal cavities or rough surfaces from trapped air
Causes:
- Insufficient mold venting
- Improper temperature or pressure during filling
- Incomplete mold filling

Solutions:
- Add or enlarge air vents
- Increase packing or holding pressure
- Balance shot volume for full cavity filling

3. Warping
Appearance: Part is bent, twisted, or deformed
Causes:
- Uneven cooling
- Pressure imbalance across the part
- Inconsistent wall thickness

Solutions:
- Stabilize mold temperature
- Design parts with uniform wall thickness
- Extend cooling time if needed

4. Burn Marks
Appearance: Dark brown or black scorch spots, typically at flow ends
Causes:
- Compressed trapped gas or air
- Excessive injection speed
- Insufficient venting

Solutions:
- Reduce injection speed
- Improve mold venting
- Check for debris in the nozzle or runner

5. Short Shot
Appearance: Incomplete part filling
Causes:
- Low injection pressure
- High resin viscosity
- Small gate or runner channels

Solutions:
- Increase injection speed or pressure
- Raise melt temperature
- Widen gate or runner size

Final Advice: Preventing Defects with Smart Equipment
Recurring molding defects often result from inadequate control over speed, pressure, or temperature. Investing in highprecision injection molding machines with smart controls can significantly reduce defect rates and improve overall product quality.

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