Plastic injection mold

The air shot will help you know if the degradation is happening in the screw or in the plastic injection mold. This is key information. The material is probably burned by either excess heat or excess shear. The suggestion to involve the Color supplier is right. The worry about the tip could be right. A hot spot could cause a burn. Shear from a cold spot or bad clearance can cause it. You need to narrow it down.

It appears that this is a hot runner mold. So far, the problem is isolated to one gate. A couple of things. The runner may have a hang up area. If so taking the manifold out and cleaning and inspecting all the runners of the plastic injection mold may help you out. There are cleaning services that can remove all organic materials from the runners without taking out the plugs. Then you can inspect the inside of the runner for hang up spots.

Probably check the screw and barrel's id surfaces for dent, scratches, that may cause material stagnate and end up degradation... would suggest before doing so, put up some other injection mold with this machine to see whether the same problems pops up. Follow Aco Mold on Facebook.