Injection Moulding Troubleshooting

A moulding defect can have several interacting causes. Confirm the material, machine and mould condition first, then review the process record. Change one variable at a time within the material supplier’s and machine builder’s recommended window.

Short shots

Check material drying and supply, melt and mould temperatures, shot size, fill speed, pressure limits, gate restrictions and venting. Confirm the screw reaches the intended transfer point and cushion consistently.

Sink marks and voids

Review part-wall thickness, packing pressure and time, gate freeze, cooling balance and material shrinkage. Check whether the packing stage can transmit pressure to the affected area before changing settings.

Burn marks, flash and splay

Burn marks can indicate trapped gas or excessive shear; inspect vents and flow restrictions. Flash can result from parting-line damage or contamination, mould wear, clamping or process conditions. Splay may relate to moisture, material degradation or contamination; follow the resin drying guidance.