Just goes to show that having a purging compound representative with actual processing experience goes a long way.
During a recent trial to remove carbon (black specs) from a 300T injection molding machine running white polypropylene resin we used Asaclean EX grade. We began to purge the barrel and screw when we noticed the nozzle tip began to clog. We removed the tip and found it to be a mixing tip with a screen filter. The injection molding techs replaced the tip with a more conventional tip that had a straight through bore. We finished purging the barrel and started the Sumitomo Demag injection molding machine. After just a couple shots, the parts were free of black specs, however we had some charring of the resin at the gate.
The tech immediately began to adjust injection speeds and temperature to correct the problem. Frustrated, the tech did not understand why they were seeing this burning. One tech had mentioned he did not understand why since they had all the original process parameters restored. They started questioning the material, colorant and even the ASACLEAN. When trouble shooting a problem it is always best to start at the beginning and look at what had changed. In this case, the techs had removed a mixing nozzle tip and replaced it with a standard one. I reminded them to replace the tip (to mixing nozzle tip), we started the machine, and within a couple shots had good parts with all process parameters were back to normal.
If you’d like more info of how you can use purging compounds to improve efficiency at your thermoplastic processing plant, contact me