3D Non-Newtonian deposition flow and thermal simulations to evaluate the scale-up potential for material extrusion of single walled ABS parts with overhang

Abstract

Material extrusion (MEX) is one of the most widely used additive manufacturing (AM) techniques for polymeric materials. In the present work, 3D simulations using Ansys Polyflow are employed to address two MEX challenges: (i) avoiding sub-optimal thermal control in the deposited part, with a too low temperature leading to a weak bond between individual strands and a too high temperature resulting in too much deformation, so that a dimensionally accurate part with the same mechanical properties of the bulk material can be printed; (ii) applicability for larger nozzle diameters away from the original application of a sub 1 mm size and going to 10 mm or more, implying a higher industrial relevance. Focus is on the scale-up potential for a single walled acrylonitrile butadiene styrene (ABS) part with an overhanging structure (e.g. 30 or 45°) and strand aspect ratios between 2 and 4, considering up to 4 layers in the simulations. The small scale results are experimentally validated, showcasing the relevance of accurate 3D deposition simulations at other scales with more difficult validation procedures. It is shown that upscaling of the MEX process changes the cooling mechanism from conduction to convection driven. It is further demonstrated how simulations can be used to predict the failure of a print at a given scale and how the printing speed can be adapted to avoid such failure.