Investigation of mechanical anisotropy of the fused filament fabrication process via customized tool path generation

To aid in the transition of 3D printed parts from prototypes to functional products it is necessary to investigate the mechanical anisotropy induced by the Fused Filament Fabrication (FFF) process. Since the mechanical properties of an FFF part are most greatly affected by the bead orientation and printed density, or solidity ratio, techniques to precisely control these variables are required. An open source Python program, SciSlice, was developed to create the desired tool paths/layer orientations and convert them into machine commands (e.g. G-Code). SciSlice was then used to develop tool paths which either directly printed tensile specimens or printed sheets from which specimens could be water-jet cut. The effects of proper bed leveling and feed wheel adjustment are noted and a careful analysis of both bead orientation and solidity ratio are presented. Printing artifacts related to turns made at the part edges are discussed having been found to have strong effects on the measure strength in the weakest orientation. Finally, it is shown that with proper bead orientation, low layer heights, and a maximum solidity ratio, tensile strengths within 3% of injection molded parts are achievable.