Injection troubleshooting

Injection Molding Troubleshooting Guide
Problem

Bubbles (cont.)

Source(s) Machine

Mold

Operator Machine

Material

Discoloration

Material

Mold

Material

Machine

MachineOperator Machine

Flow Lines

Mold

Mold Material

Machine

Mold

Cause(s) Excessive residence time in barrel Hang-up of molten material in injection barrel or runner systemContamination of injection barrel Degradation due to malfunctioning heater bands or thermocouples Defective nozzle shutoff mechanism Inefficient injection conditions Cracked injection cylinder or pitted screwOil leaking into the injection unit Sprue bushing nicked, rough, or not seating Burned material caused by improper venting Contamination caused by grease or lubricants Mold too small for machine sizeContamination of raw material Wrong material used for particular mold Inconsistent process cycle Injection screw rotation (RPM) too high Screw back pressure too low Injection speed too high Cycle timetoo short Mold temperature too low Improper gate location Insufficient venting Use of regrind that is too coarse Use of highly volatile materials Excessive moisture Injection fill speed too fast Melttemperature too high or too low Injection pressure too low Nozzle diameter too small Nozzle temperature too low Clamp opens too quickly Ejector system not level or parallel Cooling time too shortParts not packed properly Temperature too low Inconsistent mold temperature Improper gate location Parts mishandled after ejection Improper injection screw design Cycle time too short Excessive packingExcessive back pressure, screw RPM, or injection speed Nozzle too hot Injection pressure too low Gate and/or runner restrictions Condensation Resin too cold Excessive moisture in resin Resin is degradedInjection temperature too high Injection pressure too low Injection forward time too low Insufficient material feed Improper injection temperature profile Excessive injection speed Insufficient...