Computational fluid dynamics modelling of the dimensional stability of deposited layers in material extrusion additive manufacturing

Material Extrusion Additive Manufacturing (MEX-AM) is an umbrella term for a number of different fabrication methods such as Fused Filament Fabrication, Robocasting, and 3D Concrete Printing. These layer-by-layer fabrication methods are used to manufacture 3-dimensional components/structures of materials like thermoplastics, thermosets, reinforced polymers, ceramic pastes, and concrete. Finding the processing conditions that lead to high dimensional accuracy and print layer stability, for many materials, is a non-trivial task that requires a lot of experimental trial and error.
A computational fluid dynamics (CFD) model has been developed that simulates the deposition flow during MEX-AM of two layers. Three different modelling approaches (i.e., wet, semisolid, and solid bottom layer) are considered during the deposition of the second layer, thereby mimicking the printing of various materials. The semisolid bottom layer is modelled with a customized viscous solver utilizing the scalar approach to differentiate the layers' viscosity. This enables the model to simulate the structural buildup of materials such as thermosets, ceramic pastes, and concrete. The results of the CFD model illustrate its strong predictive capabilities when it comes to determining proper printing strategies that provide layer stability and high geometrical precision.