Common Plastic Molding Issues & Remedies

Low mold temperature, molten plastic temperature or low injection pressure or speed.

Air trap.

Low flowability of molten plastic.

Material thickness is too thin. Or gate size is too small.

Solidifying rapidly due to design model.

Increase pressure and packing.

Increase vent.

Enlarge runner and gate size.

Move the gate to the thicker area.

Shrinkage rate of plastic resin is too high.

Insufficient cooling time for plastic part.

Uneven ejector systems.

Adjust molding parameters or change plastic materail.

Increase cooling time.

Plastic resin is not dried sufficiently.

Injection speed is too high.

Inappropriate design of cold runner.

Ensure plastic resin is dried sufficiently.

Adjust molding parameters.

Move gate position.

Oversaturated filling.

Insufficient clamping force.

Poor mold structure: mold parting line mismatched.

Adjust injection pressure.

Change to another injection machine at more approriate tonnage.

Check mold joint surface. Repair mold if joint surface is worn.

Injection temperature is too high.

Plastic resin is not dried sufficiently.

Add too much regrind resin.

Decrease barrel temperature.

Dry plastic resin surely according to resin properties.

Decrease the ratio of adding regrind resin.

Inapproriate molding termperature.

Poor mold polishing.

Part undercut. Or no enough draft angle.

Adjust molding parameters.

Polish mold cavity side.

Increase draft angle or improve mechanical feature in mold.

Uneven material thickness.

Gate size is too small.

Molding cycle time is too short.

Modify plastic part’s structure to make the thickness distribute evenly.

Enlarge gate size.

Adjust molding parameters.

Plastic resin is not dried sufficiently.

Injection speed is adjusted inappropriately.

Gate position is inappropriate.

Ensure plastic resin is dried sufficiently.

Adjust molding parameters.

Change gate position.

Poor vent on mold.

Mold temperature or molten plastic temperature is high.

Improve mold vent.

Adjust mold temperature, decrease the time while molten plastic remaining in the barrel.