Jiangmen Licheng Technology Co., Ltd.

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BMC product surface cracks (BMC molded product manufacturer)

2018-01-13 1142
Cracks appear on the surface but do not penetrate the substrate of the product.
 
Possible reasons and corrective measures
 
1. It is prone to occur in the root cutting (inverted) area, especially when the mold is opened, there will be significant stress acting on this area. If the product is too tightly clamped in the mold, it is easy to cause cracking at the ejector pin.
 
2. Uneven or abnormal movement of the ejector pin can cause cracking during demolding.
 
3. Excessive ejection speed also leads to excessive stress on the molded product.
 
4. Fully cured parts have sufficient strength to resist the stress during demolding, requiring extended curing time and slightly increased mold temperature to ensure sufficient curing.
 
5. The shorter the activity interval or the lower the material flow velocity inside the mold, the fewer opportunities for glass fiber orientation to occur, which also forces the probability of thin parts of the component to be produced.
 
6. During molding, the material strength at the fusion line of the product is weak, which means it can resist the stress of demolding. Adjusting the scale and orientation of the paving material may change this situation.
 
7. Using external release agents is beneficial for demolding and naturally reduces stress. But the external release agent is only used for new molds, damaged chrome plated surfaces, shear edges, and other occasions.
 
Reducing the dosage of initiators or decreasing their activity is effective in increasing the strength of newly demolded parts.
 
9. The flying edge of the ejector pin should be reduced to a small size. Excessive flying edge will create resistance when the part is ejected, increasing the risk of crack formation. There is a certain gap in the ejector pin to allow air to escape, but it cannot produce excessive flying edge.
 
10. Generally, it is beneficial to make the cavity of the mold 10-15 ℃ higher than the core to eliminate the effects of mold release locking and root cutting.
 
 

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