Numerical simulation of the filling stage of injection moulding process using OpenFOAM®

Injection moulding is an important manufacturing process that allows producing large quantities of complex parts by shaping molten plastics into a mould cavity and presents several engineering/scientific challenges. Numerical simulation is a useful tool, which has been helping scientists and engineers optimizing resources like time, energy and material waste. There are several computational fluid dynamics codes available. Among them, OpenFOAM® has attracted considerable attention by both academia and industry, because it is an open source computational library which can simulate a large range of multiphysics problems and can be easily adapted to very specific needs. The purposes of this work are to evaluate the ability of OpenFOAM® to model the filling stage of injection moulding, and extend its capabilities with a new boundary condition for mimicking the mould air vents behaviour. Moreover, several exploratory studies were performed with the aim to identify the model parameters that allow minimizing the computational time, which is in general achieved when the flow is modelled with the highest possible Courant number. The new boundary condition proposed to model air vents is an optimization of the one developed in [1] for the same purpose, which comprises a different behaviour when in contact with the two phases present in the system, air and polymer melt. In brief, as it happens in practise, this boundary condition allows air to leave the mould but limits the polymer melt passage. The results attained allowed faster and more stable solutions, since it was possible to obtain physically sound predictions, even for cases with an averaged time step about 200 times larger than the highest one used in Magalhães [1], to prevent unphysical oscillations.

Acknowledgments

This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT -Portuguese Foundation for Science and Technology under the projects UID/CTM/50025/2013, PTDC/EMS-ENE/3362/2014, POCI-01-0247-FEDER-017656 and NORTE-07-0162-FEDER-000086.

References [1] Magalhães, A. C. L. “OpenFOAM simulation of the injection moulding filling stage”, Master Thesis, University of Minho, September 2016.