There is an old adage about black specks in finished parts. It goes, “You either bought ‘em, or you made ‘em!” Either way, they can be very difficult to deal with. For our purposes, we will assume that you have eliminated off-spec resin or additives as the cause of the carbon contamination.
If the black specks are the result of a problem with your process and not with your supplier you know you have an issue with either temperature or residence time. Your material is exposed to an appropriate temperature for too long a period of time, or your material is exposed to an inappropriately high temperature.
So if you made ‘em, the first step is to find out at which part of the process they were made. We have them split up: