CAUSES OF MELT TEMPERATURE VARIATONS OBSERVED IN THE NOZZLE DURING INJECTION MOLDING

摘要

Injection molders often assume that the temperature of the melt prior to injection is either equal to the barrel temperature or the temperature measured from a purge shot. Data obtained via an intrusive temperature probe in the nozzle showed a sharp increase in the melt temperature during injection followed by gradually decaying temperatures during holding and cooling. The effects that adiabatic compression, shear heating, and the initial thermal variation have on the observed temperature increase were determined through experimentation. It was found that adiabatic compression had a significant affect on the temperature increase, but the majority of the observed variation occurred as hot melt from the barrel flushed cooler melt out of the nozzle.