Injection Molding
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Unbalanced ejection of general-purpose polyethylene injection mold causing product deformation
Fenómeno del problema
The product is deformed or cracked during ejection, the ejector pin marks vary in depth, and white marks or cracks appear at some ejector pins.
Unbalanced ejection directly causes product deformation and scrap, and in severe cases the product is stuck in the mold.
Análisis de la causa
（1）The number of ejector pins is insufficient or the distribution is uneven, and the ejection force is concentrated on a few ejector pins
（2）The lengths of the ejector pins are inconsistent, and the ejection is not synchronized
（3）The draft angle is insufficient, and the friction between the product and the cavity is large
（4）The mold temperature is uneven, and the shrinkage of each part of the product is different, resulting in large local clamping force
（5）The ejection speed is too fast, and the impact force causes the product to deform
Solución
（1）Increase the number of ejector pins and distribute them reasonably to ensure that each ejector pin is evenly stressed
（2）Check and adjust the length of each ejector pin, and the synchronization error should not exceed 0.02mm
（3）Increase the draft angle, at least 1-2° for polyolefin materials, and polish the side of the cavity
（4）Control the mold temperature uniformly, and the temperature difference between each part should not exceed 5°C (within the range of 30-80°C)
（5）Reduce the ejection speed and adopt a slow-fast-slow ejection speed curve
Conclusión clave
Unbalanced ejection is caused by the design of the ejector pin system or large demolding resistance, and the ejector pin layout and demolding conditions need to be optimized.
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