Process control is an important factor for improving the performance and consistency of thermoplastic parts manufactured by injection molding processes. A critical process parameter for manufacturing of high quality plastic parts is cavity pressure. This paper presents direct numerical simulation results of a new manufacturing concept developed to improve injection molding processing for all runner types by monitoring shot to shot product quality and controlling the filling of multi-cavity molds in real time. A cold runner system supplying polymer melt to a two-cavity mold incorporating mechanical valves in the runner systems was modeled. Each valve was controlled independently to meter flow and pressure to its portion of the mold. Simulations were performed for two different materials: PPS Ryton R-4-200 and LCP Vectra E130D-2. Shear-rate dependence of viscosity of the materials is modeled through the Cross rheological equation. Flow rates and maximum shear-rates through valves were calculated and the results of the simulations were analyzed to validate the concept of individual cavity filling modification. Flow through one valve system leading to a single cavity was simulated first, followed by flow through two-valve system for filling two cavities. For one valve simulations, pressure at the inlet was specified, whereas for flow through two-valve system, volumetric flow rate at the inlet was supplied for simulations. It was concluded that the flow control concept developed was numerically validated, and it was shown that the valve system proposed here is applicable to control melt flow through cavities at industrial manufacturing facilities. The future directions for the continuing project are also discussed.
Additive manufacturing of heat-sensitive polymer melt using a pellet-fed material extrusion
