Numerical study of the multi-strand deposition using a boundary-conforming free-surface approach

  • González, Felipe (RWTH Aachen University)
  • Elgeti, Stefanie (TU Wien)
  • Behr, Marek (RWTH Aachen University)

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A numerical study of the multi-strand deposition in a fused deposition modeling (FDM) process is carried out in this work. The FDM process is a popular fabrication process mainly used in manufacturing functional parts and rapid prototyping, Due to the complexity of simulating the process, it is common to focus the study on a single-strand extrusion [1]. This work extends the FDM simulations presented in [1] to a multi-strand extrusion simulation. A spline-based representation of the previously printed strand boundaries is used to include the effect of neighboring strands in the simulation. In contrast to the single-strand simulation, the focus moves to compute the interfilament void remaining after every deposition, which is responsible for the porosity of the final object. Accurately predicting a quantity like porosity is crucial in an FDM process since it directly impacts the final object's mechanical properties. The simulation framework is based on the stabilized finite-element method. The arbitrary Eulerian-Langrangian (ALE) formulation addresses the deformation of the domain and a boundary-conforming free-surface approach [2] is used to track the filament motion. Furthermore, by using a boundary-conforming approach, the computational domain matches exactly the filament shape and allows an accurate description of the free-surface movement. The mesh motion is enhanced by using a sophisticated mesh-update method called the surface-reconstruction virtual-region method (SR-VR) [3], which is designed for problems with large mesh translation and topology changes. Particularly for the FDM simulation, the SR-VR method allows augmenting the domain with new elements, which translates into extruding new material from the printed nozzle. The Cross-WLF viscosity model is used to represent the shear rate-dependent and the temperature-dependent behavior of the polymer material.