How to Remove Stuck Parts from Injection Molds

Sticking is a common injection fault where cooled parts fail to release from the cavity or core.Improper handling can scratch cavities, bend ejector pins, or damage inserts.The safe approach emphasizes gentle methods, prioritizing mold protection and personnel safety.Following standardized procedures ensures quick resolution with minimal risk.

Safety Preparation Before HandlingBefore any operation, switch the machine to manual mode, stop heating, and disable automatic operation.Confirm the mold is fully open and the ejection system is in a safe position.Prepare soft tools: copper blades, nylon pry bars, soft brushes, air guns, and cotton swabs.Steel needles, screwdrivers, and hard metal tools are strictly prohibited to prevent surface damage.

Wear protective gloves and goggles to avoid injury from flying chips or high‑temperature surfaces.

Ejector System Assisted Removal

For mild sticking, use short, repeated ejector pulses to gently vibrate the part loose.Use an air gun to blow along edges to reduce vacuum and adhesion.Adjust ejection pressure moderately if needed, but avoid sudden high force that may break the part.Maintain balanced force to prevent uneven stress and breakage.

Cooling Shrinkage RemovalCooling uses the higher shrinkage rate of plastic compared to steel.Apply uniform cool air for 1–3 minutes to shrink the part and reduce wrapping force.This works well for PP, PE, ABS, PC, and most structural parts.After cooling, use the ejector to remove the part smoothly.This method is non‑invasive and highly recommended for moderate sticking.

Local Heating Softening RemovalFor rigid, high‑shrink‑resistance materials like PC and PA, mild local heating can soften the surface layer.Increase mold temperature slightly or use a low‑temperature heat gun at a distance.Heat briefly to reduce adhesion without carbonizing plastic or annealing mold steel.Allow brief cooling before ejection to avoid deformation.

Manual Auxiliary Removal with Soft ToolsIf ejection alone fails, use copper or nylon tools to gently pry from edges.Apply force evenly at multiple points to avoid breaking the part inside the cavity.Work slowly and carefully to protect both the part and mold finish.

After removal, clean away all chips and residues.

Disassemble Mold Inserts for Removal

For complex undercuts, deep cavities, or broken parts, carefully remove inserts or slides.Mark positions before disassembly to ensure accurate reassembly.Once loosened, remaining material can be safely extracted.Reassemble, verify alignment, and test movement before resuming production.

Post‑Removal Inspection and RecoveryAfter resolving the stuck part, clean the cavity thoroughly.Apply a thin, uniform layer of release agent.Manually test opening, closing, and ejection several times.Run 1–2 trial shots to confirm stable demolding before automatic production.