Quality monitoring and control for plasticization of acrylonitrile-butadiene-styrene regrind polymer in injection molding

To meet net-zero carbon emissions in injection molding, it is desirable to use regrind polymers in plastic parts fabrication. However, the quality of regrind polymer differs from virgin polymer due to the effects of temperature, pressure, and shear stress in the prior molding process. Consequently, the molded components differ in quality compared to those made from virgin material. This study investigates the feasibility of enhancing the quality consistency of regrind plastic components by controlling melt quality in plasticization. The evaluation of melt quality involves extracting two quality metrics from the pressure signal (i.e., the peak pressure and the pressure integral). They are then used to adjust the plasticization parameters as required to ensure that the weight and dimensions of the final regrind parts approach those of parts produced using virgin polymer. The experimental results show that the pressure integral effectively indicates the quality variation of the molded part during the injection molding of regrind polymer. Notably, by adjusting the back pressure, the quality of the molded part closely resembles that of the part made from virgin feedstock after six shots.