Improving the strength of Fused Filament Fabrication parts by non-planar alignment of material extrusion with stress vectors

Current applications of Fused Filament Fabrication in additive manufacturing tend to produce heavily anisotropic parts. This is largely due to the discretization of heterogeneous planar layers, resulting in weak thermal fusion bonding that fundamentally limits the strength of end-use parts. To improve the mechanical properties of these parts, this work develops a novel method to generate non-planar, stress-aligned layers and toolpath plan that is feasible on consumer hardware. The approach uses a region-based stress alignment scheme starting with select layers and preserving local boundaries and printability. This approach relies on the local rotation of sets of points on a surface to achieve coplanarity between mesh regions and their largest tensile stresses. Interest regions are weighted to high stress areas using local von Mises stress, with intermediate layers generated from linear interpolation between respective sets of aligned regions. The fitness of model slicings is assessed by analyzing the intrinsic coplanarity of each first principal stress vector on the sliced layers to that of the finite element mesh indicating how close layers are to the ideal alignment. Simulation results show fitness scores increased by up to 120% from commercial planar slicing. Physical testing of printed samples confirms mechanical property improvements and more ductile failure modes.