Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and molding systems continue to produce defective components during production. The capability of the injection molding process is limited by the thermal and flow dynamics of the heated polymer melt.
This paper discusses some of the difficulties posed by complex and distributed nature of the injection molding process. The flow and thermal dynamics of the process are analyzed with respect to transport and rheology. Then, two novel processing methods are described to enable in-cycle flow, pressure, and thermal control. Simulation and experimental results demonstrate effectiveness of these innovations to increase the consistency and flexibility in polymer processing. Such system design changes simplify the requisite control structures while improving the process robustness and productivity.