Analysis of common injection molding defects | poor exhaust

Surface phenomenon
There are black stains on the surface of the product away from the gate and flow line. Sometimes products are not fully filled in these places.
Physical causes
The air wrapped in the mold is easy to be affected by high pressure and high temperature. Due to the high injection speed, the molten material far away from the material head will often be at the joint and material flow line. Coking occurs after edges and blind holes.
The main reason is that coking is easy to occur at high temperature. Because the mold cavity used in modern times only contains a few parts, almost all of them are produced by electrical erosion, and it is the most difficult problem to let air out. In the past, mold inserts were used to exhaust air through small gaps.