Persistent deposits in the screw
Cost-efficient color and material changes as well as cleaning processes are always a major challenge for every practitioner in plastics processing. They often take several hours to days and therefore cause immense costs.
One cause of these long cleaning processes often are the deposits in the screw. There are also flow dead zones in the bottom of the screw. As in all other dead zones, the plastic is exposed to the high temperatures for too long, burns, builds up layer by layer and above a certain size, is carried away by the flowing plastic melt (black specks).