TROUBLESHOOTING GUIDE FOR INJECTION MOLDING
The following table provides an overview of most problems/defects. Please click on the desired problem phrase for a quick view of problems and potential causes:
Please click a problem phrase to the left
Burn spots on part Probable Causes - Injection rate too high
- Screw rpm too high
- Back pressure too high
- Clamp pressure too high
- Venting
Burn marks at gate Probable Causes - Gate size
- Restricted gate
- Injection speed too high
- Back pressure too high
- Mold temperature too high
- Front zone temperature too high
Discolored streaks or chunks Probable Causes - Incompatible color or additive carriers
- Prior runs contaminated plastification system
- Insufficient blending of color concentrate
Distorted parts (warping) Probable Causes - Material orientation
- Molded part stresses
- Difference in packing density
- Ejection operating improperly
Flash on parting line Probable Causes - Injection pressure too high
- Melt temperature too high
- Mold function incorrect
Material drool from nozzle Probable Causes - Material degradation
- Pressure build up
- Barrel and nozzle temperature
Part dimensions too large Probable Causes - Mold over-packed
- Mold designed incorrectly
Part dimensions too small Probable Causes - Mold is under-packed
- Mold temperature too high
- Mold design
Part sticks in mold cavity/sprue Probable Causes - Part over-packed
- Part not sufficiently cooled
- Mold design
- Tool steel
Poor finish Probable Causes - Mold fill is too slow
- Mold function incorrect
Poor surface detail Probable Causes - Mold filling improperly
- Packing conditions improper
- Polymer cooling rate too high
Poor welds on part Probable Causes - Polymer cooling rate too high
- Mold design
Short shots prevent complete mold filling Probable Causes - Available melt volume insufficient
- Mold has high pressure drop
- Mold function incorrect
Silver streaking Probable Causes - Material has trapped moisture
- Melt temperature too high
- Mold condensation
Sink marks Probable Causes - Part design
- Mold function incorrect
- Processing parameters
Splay marks near gate Probable Causes - Low pressurization at gate area
- Mold set up incorrect
Voids in parts Probable Causes - Material in core sets up slower than surface material
- Moisture in the pellets
The AnswerPersonSM