Optimization of mold thermal control for minimum energy consumption in injection molding of polypropylene parts

The environmental impact of the injection molding process is mostly due to electricity consumption. This is particularly significant for packaging products, which are the largest application sector for the plastics industry. In this work, electricity consumption measurements of the process were performed, considering a large production plant processing polypropylene packaging parts. In particular, the electricity consumption of mold thermal control was analyzed and minimized through a representative case study. The effects of alternative configurations of cooling channels and different process parameters were experimentally and numerically investigated, considering both the electricity consumption and the molded parts quality. The results indicated that the industrial common practice of maximizing the water flow rate and connecting the mold cooling circuits in parallel, to minimize the increase of coolant temperature, can be satisfactory in terms of part quality but not optimal when considering the energy consumption related to mold thermal control. By setting the hot runner and nozzle temperatures to the lowest suitable values, the coolant flow rate could be reduced significantly (−66%) without compromising the quality of the molded parts and reaching a minimum value of the energy consumption.