A multiphase Eulerian approach for modelling the polymer injection into a textured mould

Micro-injection moulding is frequently used for the fabrication of devices in many different fields such as micro-medical technologies, micro-optics and micro-mechanics thanks to its effectiveness for mass production. This work focuses mainly on offering numerical methodology to model the injection into textured moulds. Such approach can predict the different filling scenarios of the micro-details and consequently can provide optimal operating conditions (mould and melt temperatures, flow rate) according to the desired final part quality. In fact, numerical simulations made with industrial software can only describe the injection process at the macroscopic scale where the micro details are not detected. Although the melt temperature and front evolution are tracked throughout time, neither the micro details nor the local heat transfer are properly represented. Since the latter impacts the local viscosity and solidification, simulation of both mould and cavity temperature evolutions is primordial to insure a complete and accurate representation of textured mould filling. The present computations are made at both macro- and micro- scales by using a full Eulerian approach in which the three phases (melt, mould and air) are described by level-set functions. Our numerical approach is checked to the replication of a textured mould for which two dimensional computations are relevant. This replication is properly modelled by taking into account viscosity dependence with temperature in the thermal boundary layer at the melt/mould interface. In particular the expected solidification below a specific temperature is taken into account by either increasing drastically the viscosity or by imposing a vanishing velocity by penalty method. The influence of flow rate and mould temperature are also analysed whereas it is shown that the surface tension can be neglected during injection stage.