Numerical Simulations of Fused Filament Fabrication

Numerical model and simulations of Fused Filament Fabrication where a filament of hot, viscous polymer is deposited to “print” a three-dimensional object, layer by layer, are presented. A finite volume/front tracking method is used to follow the injection, cooling, solidification and shrinking of the filament. The injection of the hot melt is modeled using a volume source, combined with a moving nozzle, modeled as an immersed boundary. The polymer is taken to be a viscoelastic fluid and an evolution equation for the confirmation tensor is solved along with the conservation equations of momentum and energy. As the polymer solidifies, the stress is found by assuming a hyperelastic constitutive equation. The accuracy and convergence properties of the method are tested by grid refinement studies for a simple setup involving two short filaments, one on top of the other. The effect of the various injection parameters, such as nozzle velocity and injection velocity are briefly examined and the applicability of the approach to simulate the construction of simple multilayer objects is shown. The role of fully resolved simulations for additive manufacturing, their use for validating models of the physics, and as the ``ground truth’’ for reduced order models, is discussed.