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.
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.