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What are the reasons for the occurrence of black spots in injection molded parts

2022.03.21
The creation of black / brown specks is one of the most common defects you’ll find in injection molding.  This defect can often be a nightmare for processors as they can appear and quickly disappear at irregular intervals during the molding process.  Black specks tell the processor that there is certainly some level of contamination present within the system.There are times when a post-molded part can come in contact with grease or dirt on the molding surface.

But if the injection screw barrel for injection machine defect is within the molded part then a processor can be sure that there is contaminated material present in the system.It can be tough to get control of degraded material with processing adjustments alone.  A good commercial grade purging compound like Asaclean is the best solution for purging the system of degraded material so the processor can reestablish the process with a clean screw and barrel.  It is always a good idea to use a purging compound when changing over resins that will run on the same press.  This will ensure that the previous resin that could be more heat sensitive is not lingering in the system to possibly cause problems with the next run.

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