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Written by Jinnfeng Plastic on . Posted in News.

Solution to sticky mold in injection molding

‌Solution to Sticky Mold in Injection Molding‌ In the realm of injection molding, main runner sticking poses a significant challenge. It occurs when the main runner of an injection-molded product fails to detach smoothly from the plastic mold during the demolding process. This issue not only hinders production efficiency but may also compromise product quality.

sticky mold in injection molding

Causes of Main Runner Sticking

  • Improper Cooling Time: A commonly encountered reason for main runner sticking is the inadequate setting of cooling time during injection molding. When the cooling time is insufficient, the main runner remains partially uncooled and unsolidified, making it difficult to separate smoothly upon mold opening. Adjusting the cooling time appropriately is crucial in preventing this issue.
  • Insufficient Demolding Slope Design: Another factor contributing to sticking is the inadequate design of the demolding slope for the main runner. The main runner necessitates a specific slope to facilitate smooth ejection during demolding. If the slope is inadequate, it should be increased to diminish demolding resistance.
  • Dimension Mismatch: Improper matching dimensions between the main runner bushing and the injection mold nozzle can lead to leakage, ultimately causing main runner sticking. Ensuring precise matching dimensions during mold design and manufacturing is essential to prevent leakage.
  • Surface Roughness and Cold Well Setting: The roughness of the main runner surface and the absence of a cold well also play pivotal roles in affecting demolding. A rough main runner surface without a cold well increases demolding difficulty. Improving surface roughness and appropriately setting cold wells can reduce demolding resistance.
  • Low Nozzle Temperature: Lastly, a low temperature of the injection molding machine nozzle can contribute to main runner sticking. When the nozzle temperature is too low, it impairs the fluidity of the plastic melt, thereby enhancing adhesion between the main runner and the mold. Increasing the injection temperature appropriately ensures good plastic melt fluidity.

Conclusion

Main runner sticking in injection molding stems from various factors, but by adjusting the cooling time, enhancing the demolding angle of the main runner, ensuring precise mold matching dimensions, refining surface roughness, setting cold wells, and optimizing injection temperature, this issue can be effectively mitigated. These measures contribute to enhancing production efficiency and product quality in injection molding.