Injection Moulding Troubleshooting Problems & its Recommendations

Brittleness
Reduce screw speed
Reduce back pressure
Reduce cylinder temperature
Check for material contamination
Dry material

Blisters
Increase back pressure
Reduce screw speed
Dry material

Excessive Flash
Increase back pressure
Reduce cylinder temperature
Reduce injection pressure
Clean mold faces
Increase clamp pressure
Check mold faces for proper fit

Gas Burns
Increase size of vent
Increase size of gate
Reduce injection speed

Poor part to part Uniformity
Check heater bands, controllers and thermocouples
Check hydraulic system for pressure variation
Check hopper for material bridging

Oversized Part
Increase mold temperature
Reduce overall cycle time
Reduce injection speed
Reduce injection and holding pressure
Reduce cylinder temperature

Silver Streaking
Increase mold temperature
Decrease screw speed
Dry material
Increase injection speed
Increase cylinder temperature

Poor Weld Lines and Poor Surface Finish
Increase cylinder temperature
Increase mold temperature
Increase injection pressure
Increase injection speed
Change gate location
Vent Mold
Clean cavity surface

Short Shots
Increase size of
- Sprue
- Runners
- Gates

Clean vents
Increase back pressure
Incorporate or enlarge venting
Increase amount of material
Increase injection pressure
Raise material temperature
Raise mold temperature
Increase injection time

Undersized Part
Increase holding time
Increase cylinder temperature
Increase size of gate
Decrease mold temperature
Increase injection and holding pressure
Increase injection speed

Sink Marks
Reduce cylinder temperature
Increase holding time
Increase holding pressure
Reduce mold temperature
Increase gate size
Increase injection pressure
Locate gates near heavy cross sections

Warping
Reduce molded in stress
- Raise molded in stress
- Reduce injection speed
- Relocate gating

Check for uneven mold temperature
Reduce temperature of ejected part
- Increase cooling time
- Lower mold temperature
Redesign ejection mechanism

Voids
Increase injection pressure
Reduce cylinder temperature
Use dry material
Increase mold temperature