Coupled injection moulding simulation-thermal and mechanical simulation method to analyse the operational behaviour of additively manufactured polymeric injection moulds

The appearance and the widespread application of additive manufacturing (AM) technologies has brought a sweeping change to the polymer processing industry. Hybridization of the technologies like printing moulds for conventional injection moulding opens new opportunities because parts can be manufactured in low volumes fast and cost effectively. This way, the greatest limitation of injection moulding can be overcome, which is economic viability only at large-volume production. We manufactured a low-volume mould insert from a polyamide powder with a Powder Bed Fusion (PBF)-based technology: Selective Laser Sintering (SLS). We performed material tests to determine the stiffness and the creep compliance of the material in the relevant temperature region. These parameters determine the suitability of the material for prototype mould making and they are inputs for the simulation of prototype moulds. We also applied comprehensive measurement technology consisting of simultaneous strain, temperature and cavity pressure measurement to get a broad view of the operational behaviour of the insert. We introduced a novel coupled simulation method, which can forecast the thermal and deformational state of the SLS-printed mould insert during operation. This coupled method first uses injection moulding simulation to create the mould mesh and to calculate the transient pressure and temperature fields during operation. The results are then exported to a finite element mechanical simulation, where a transient thermal and then a structural simulation is run. The transient thermal simulation is necessary to calculate the temperature field of the mould components, while the structural simulation requires the pressure load input from the injection moulding simulation and the temperature field from the transient thermal simulation. Our simulation method proved suitable for modelling the operational behaviour of polymeric mould inserts.