Modeling and evaluation of freeform extruded filament based on numerical simulation method for direct ink writing

Direct ink writing (DIW) is an extrusion-based additive manufacturing (AM) technique. One of the required factors for printing quality in DIW to extrude continuous and tubular freeform extruded filaments (FEF) with diameters close nozzle inner diameter. This paper established a simulation model FEF volume fluid (VOF) method then evaluated based on results. First, properties including density, surface tension coefficient, rheological were determined by tests. Then, was using VOF software OpenFOAM two evaluation indicators, mean diameter stability, proposed evaluate FEF. Two inks, cellulose Nivea Crème, used under three levels piston velocity verify universality different inks variable process parameters. The prediction accuracy verified as relative error between experimental results less than 10.22%. In this work, it found that (1) needed be set higher minimum value overcome yield stress successfully filaments; (2) decreased while stability firstly increased increased. indicators gave accurate effective framework analyze effect FEF, characterize printability, find suitable printable windows parameters DIW.