A robust thermomechanical sintering simulation for 3D printed parts with internal lattices

Most parts printed with additive manufacturing used a bioinspired filling strategy with a dense shell and internal lattices. Such strategy helps optimizing the part strength/weight ratio through topology optimization and significantly improve the printing time and quality. However, simulate such complex porous inner structures would imply calculation instabilities and a colossal increase of the simulation time through the high number of degrees of liberty. Consequently, there is today no robust solution to simulate the sintering of printed parts with inner lattices, despite the fact that it represents the majority of the printed objects. This study circumvents this issue by a continuum approach that can simulate real parts and the complex lattice behavior with a computation time representing a small fraction of the sintering time. The lattice geometry is first simulated by a sub-model with identifies their effective moduli for different porosity. These effective moduli are then used to simulate the sintering in the lattices zones of the printed parts. The lattices also significantly decrease the inner part thermal conductivity. An additional sub-model is used to extract the effective lattice thermal conductivity by a simulation considering the thermal conduction in the lattice skeleton and the cavities thermal radiation and convection. A robust thermomechanical simulation is then possible to quickly and efficiently predict the parts firing with the developed thermal gradients and the distortions it results as well as the inherent anisotropy that greatly influence the final part dimensioning.