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Home » Plastic molding » ejector marks injection molding cause and troubleshooting

ejector marks injection molding cause and troubleshooting

January 11, 2019 by mechanicaleng blog Leave a Comment

In injection molding process, ejector marks is a concave or a convex on the surface. Samples are  stick in the mold under force of ejector system, it will create holes on products.

ejector marks injection molding
ejector marks injection molding

Cause of ejector mark.

+ Sample doesn’t have a draft angle at boss, rib. It is difficult to push sample out of the mold. Samples will have scratch, bite.

+ When design a mold, ejector pin is small or it is thin position.

+ Injection machine setup is not good, if we use high force for ejector system.

+ Cooling time is low so sample is not cold, sample will deform under force of ejector system.

+ Temperature difference between mold and ejector system.

How to improve ejector marks defect injection molding?

+ If sample has scratch at boss, rib -> lapping the mold at these position.

+ If ejector pin is too small, change to new ejector pin with bigger diameter, or change ejector pin to new position, we can change to rib area.

+ Increase cooling time.

+ Increase thickness of product  at ejector mark if we can.

+ Reduce holding pressure, holding pressure time, or mold temperature.

+ Check the mold, if ejector is over core surface, re-set ejector system.

 

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Filed Under: Plastic molding Tagged With: molding defect

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