I’ve talked in past columns about measuring melt temperature and the four evils of overheating: Polymer degradation, cooling problems, sizing problems and the effect on additives. Summertime seems like a good time to revisit and expand on this theme.
Most of the energy needed to melt the plastic comes from the motor, but external heaters are also important for small machines, some twins, high-melting polymers and most extrusion coating. They are also necessary in all extruders for startup.
Many lines have water cooling in the takeoff, directly or through rolls, as well as on the barrel (including a separate circuit in the feed casting) and sometimes inside the screw. Make sure those circuits are running normally, that all controllers are working OK, and systems are kept clean and free of hard-water buildup, which may limit cooling capacity.