Manipulating magnetic anisotropy in fused filament fabricated parts via macroscopic shape, mesoscopic infill orientation, and infill percentage

The application space for three-dimensional (3D) printing, such as fused filament fabrication (FFF), has grown significantly through the use of high-performance composite materials. While the mechanical, thermal, optical, and electrical properties of additive manufacturing (AM) polymer composites are being actively studied, the magnetic properties of AM parts have seen much less attention. Prior research has shown that the structural print settings for FFF influence the magnetic properties of the printed part (Bollig et al., 2017). However, the structural hierarchy present in the FFF process complicates a simple analysis of how these magnetic differences arise. Here, a magnetic filament consisting of polylactic acid (PLA) polymer and 40 wt% iron was used to print a variety of samples to investigate how the macroscopic sample shape and the mesoscopic infill orientation and infill percentage affects the magnetic properties. The array of samples systematically covered different aspect ratios (length:width), edge contours (rectangular vs. ellipsoidal), two infill orientations (long axis alignment vs. short axis alignment), and varying infill percentages. The key results show that the highest magnetic susceptibility was seen for magnetic fields applied parallel to the infill orientation. The macroscopic geometry increased the magnetic susceptibility parallel to the long axis of the sample. Lastly, certain factors, such as edge contours and infill percentage, only affected the magnetic susceptibility when the magnetic field was applied transverse to the infill orientation, but had no effect when field was applied along the infill direction. Elucidating how the part shape, infill orientation, and infill percentage affects the magnetic properties of AM parts will help the community better understand how an FFF process can be utilized to make optimal magnetic components, such as transformer cores, electric motors, and electromagnetic interference shielding.