Computer Simulation and Experimental Investigations of Wall-Thickness Distribution in High Impact Polystyrene and Amorphous Polyethylene Terephthalate Thermoformed Parts

Abstract

The focus of this study was to determine the influence of molding parameters such as types of mold, sheet and mold temperatures on the wall-thickness distribution of thermoformed parts. The materials used were high impact polystyrene (HIPS) and amorphous polyethylene terephthalate (A-PET). All the thermoformed parts were molded only after the machine had attained a steady state with respect to the preset sheet temperature from 130 to 170 oC and mold temperature of 30, 60, and 80 oC, respectively. Several settings were tried and those leading to an overall satisfactory quality with regard to visual properties were finally chosen. Furthermore, the commercial simulation package (T-SIM) was also extensively verified against experiments performed with simple mold geometry as well as with a more complicated part. Both simulated and measured results suggested that in order to obtain a more uniform wall thickness throughout the entire area of a thermoformed part, it was necessary to use a plug mold as well as a suitable mold temperature. The numerical results were in good agreement with the experimental ones, which suggested that the simulation program can be used as a valuable tool for avoiding the time-consuming and burdensome trial-and-error process.