Variable Extrusion Width for Interlocking Features in Fused Filament Fabrication 3D Printing

Following from developments in continuously variable extrusion width in fused filament fabrication additive manufacturing, this work explores the combination of in-plane bead width variation with bead trajectory variation as a technique to improve in-plane strength in polymer material extrusion additive manufacturing. Sinusoidal in-plane waveforms are used for the extruder trajectory instead of maintaining a straight line. The varied bead width, in conjunction with the non-straight bead trajectory, reduces anisotropy of strength within the layer. The findings apply to fully dense infill of single layers, commonly called horizontal perimeters in common slicing/toolpath planning computer programs. Experimental tensile testing results show a 48.6% reduction in anisotropy of tensile strength driven by 43% and 29% increases in the ultimate tensile strength in the 0° and 45° orientations, respectively. However, this comes at the cost of 99.6% reduction in toughness in the 90° orientation. We also present the principal concept behind the machine code generating script, that allows for the increase and decrease of the extruded bead width continuously along the extruded bead.