Poor Demolding / Ejection Defects:
Poor demolding occurs when the mold structure is unreasonable, manufacturing precision is insufficient, or overfilling makes it difficult to eject the part. It can also cause the part to be scratched, stretched, or deformed after ejection.
| 16.1 Causes | 16.2 Solutions |
|---|---|
| 16.1.1 Mold surface not smooth. | 16.2.1 Polish the mold to meet surface finish requirements; reduce demolding force. |
| 16.1.2 Mold draft angle insufficient. | 16.2.2 Increase the draft angle. |
| 16.1.3 Large gaps at mold inserts, causing flash. | 16.2.3 Tighten the mold, repair and grind mold surfaces. |
| 16.1.4 Injection time too short or too long. | 16.2.4 Adjust injection time to make shrinkage uniform and facilitate demolding. |
| 16.1.5 Mold core has no vent, forming vacuum. | 16.2.5 Modify mold design to allow air in during demolding, balance pressure, increase draft, reduce mold opening speed. |
| 16.1.6 Improper mold temperature (moving/ fixed side). | 16.2.6 Adjust mold temperatures. |
| 16.1.7 Mold surface has scratches. | 16.2.7 Repair the mold by polishing, welding, or scrapping if necessary. |
| 16.1.8 Ejector system malfunction. | 16.2.8 Repair ejector system for smooth demolding. |
| 16.1.9 Long holding time, high material/mold temperature, excessive feed, long injection time, large gate size. | 16.2.9 Reduce injection/holding time, reduce feed, adjust mold, decrease gate size. |
| 16.1.10 Improper release agent. | 16.2.10 Use a suitable release agent. |
| 16.1.11 Pull rod failure. | 16.2.11 Repair the pull rod. |
| 16.1.12 Material stuck between nozzle and gate bushing; gate bushing sticks to mold. | 16.2.12 Repair nozzle and gate bushing to ensure proper fit. |
| 16.1.13 Large cavity deformation or mold rebound causing part to stay in cavity. | 16.2.13 Adjust process parameters or repair mold. |
| 16.1.14 Poor cooling system; cooling time too long or short. | 16.2.14 Repair mold or adjust cooling time. |
| 16.1.15 Movable core not demolding in time. | 16.2.15 Repair core for timely demolding. |
| 16.1.16 Insufficient feed. | 16.2.16 Increase feed quantity. |
| 16.1.17 Brittle material, prone to sticking, high shrinkage. | 16.2.17 Use brittle-resistant materials; ensure mold surface finish and larger draft angle. |
| 16.1.18 Part geometry unfavorable for demolding; wall too thick/thin or insufficient strength. | 16.2.18 Make wall thickness as uniform as possible, increase draft, add fillets at sharp corners without affecting use. |
| 16.1.19 Hot runner temperature too high or thermocouple failure, molten material entering mold. | 16.2.19 Lower hot runner temperature or replace thermocouple. |
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