A Design Method for Graded Density Components by Polylactic Acid Foaming via Material Extrusion

The availability of foaming materials with properties that vary according to the heat transferred to the filament in the fused filament fabrication (FFF) process provides the opportunity to develop new design methodologies that allow the exploitation of the range of characteristics offered by these materials. In this work, an integrated CAD-CAM method to realize graded density foamed components via FFF is proposed. The method consists in the post-processing of a G-code file obtained from a CAD model according to functional requirements defined by a density map volumetric model. The method relies on the material property-process parameters correlation to drive the foaming in a specific extruder configuration. The temperature effect on extrusion width and density is experimentally investigated as the primary process parameter driving the foaming behaviour of a commercially available filament. Based on the density map of the volumetric model and the experimental characterization, temperature and extrusion amount are updated in the G-code file. The method is applied to a simple buoyant 3D shape to ensure its orientation in water.