Experimental Validation of a Simulation Model for the Non-Return Valve Performance during the Injection Phase of an Injection Molding Cycle

A CFD model which simulates the flow of a polymer melt during an injection molding cycle is developed using the simulation software Ansys Fluent. With this model the closing behavior of a ring-type non-return valve during the injection phase is investigated. The flow conditions in the barrel from the metering zone of the screw to the nozzle tip are considered based on a viscous, compressible and non-isothermal polymer melt flow. In a quasi-static approach, the velocity of the non-return valve sliding ring is determined based on the equilibrium of forces acting on the sliding ring. The simulation model is validated by performing injection molding experiments for two thermoplastic polymers (PP and HDPE) with varying injection flow rates. Experimental data for validation is obtained by three melt pressure sensors which are installed in the barrel of the injection molding machine. The accuracy of the simulation model is analyzed by comparing the melt pressure occurring behind the non-return valve in simulation and experiment. The simulation results are in good agreement with the experimental data for the materials and setting parameters considered.