An investigation of melt temperature development in injection molding and extrusion

This work focuses on understanding the melt temperature development in injection molding machines and extruders. An experimental program was undertaken to measure melt temperatures and pressures in real time and study them as functions of machine and material parameters. Melt temperature was found to be most sensitive to screw speed, back pressure, injection speed and polymer rheology. It was also determined that an injection molding process never approaches the steady state of an extrusion process. The experimental technique developed was also able to characterize melt temperature and melt pressure within a screw channel.; Application of the experimental program for melt temperature development was studied in reference to recycling. Resins with different percentages of regrind were molded. Two control strategies were used to maintain constant part properties in the presence of changing feedstock.; Mathematical models were developed to predict the temperature rise during melt conveying. The models used were the existing extrusion analyses, as well as an alternative melt conveying analysis. This alternate melt conveying analysis was also extended to the solids conveying section. The predictions of the alternate conveying analyses were in agreement with data collected in-house as well as literature data.