How to Address the Issue of Thin and Easily Broken Ejector Pins in Injection Molds

 1. Optimize the Ejection Process  

Adjust ejection parameters to minimize stress on delicate ejector pins.  

Reduce ejection speed: Excessively high ejection speeds generate significant impact forces, increasing the risk of breakage in thin ejector pins. A moderate reduction in speed can mitigate this risk.  

Implement multi-stage ejection: Utilize the multi-stage ejection capability of the injection molding machine. Initiate the first stage at a low speed and short stroke to release vacuum adhesion, followed by standard ejection in the second stage. This approach effectively reduces peak impact loads.  

Verify ejection stroke: Ensure the stroke is precisely calibrated to fully eject the part without over-extension, which may cause the ejector pin to lose guidance support and become unstable.  

Maintain proper lubrication: Regularly apply high-temperature mold release oil to the ejector pins to minimize friction between the pins and the mold core.

2. Revise Mold Design  

The most effective and long-term solution is to replace fragile, undersized thimbles with larger-diameter counterparts.  

This modification requires adjustments to the hole positions in both the mold core and the ejector plate. Although this involves higher initial costs, it provides a durable and reliable resolution.

3. Modify Ejection Methodology  

When spatial constraints prevent increasing the pin diameter, alternative ejection mechanisms should be considered.  

Use flat thimbles: In narrow regions such as rib areas, flat thimbles offer a greater cross-sectional area and superior resistance to bending compared to round thimbles.  

For boss columns with high shrinkage forces, employ stripper pins, which provide a broader and more uniform ejection surface.  

For deep cavities or thin-walled parts, consider air-assisted ejection systems. These introduce compressed air from within the cavity to disrupt vacuum formation, significantly reducing demolding resistance.  

Apply push plate ejection: For large, deep-container components, push plates offer full-surface contact, distributing ejection force evenly and minimizing localized stress compared to point-contact ejector pins.

4. Enhance Mold Structural Integrity  

Incorporate guide pillars: Install guide sleeves on the ejector plate to ensure precise alignment and smooth movement of the ejector system, thereby preventing lateral shear forces due to misalignment.  

Polish ejector pin bores: Inspect and refinish worn pin holes to reduce friction and improve operational smoothness.  

Inspect for and correct undercuts: Conduct a thorough mold inspection to identify any unintended undercuts that may contribute to excessive part retention force, and rectify them accordingly.