Polymer-bonded anisotropic SrFe12O19 filaments for fused filament fabrication

In this publication, we describe the extrusion process and the properties of polymer-bonded anisotropic SrFe12O19 filaments for fused filament fabrication (FFF). Highly filled polyamide 12 filaments with a filling fraction from 40 vol. % to 55 vol. % are mixed and extruded into filaments with a diameter of 1.75 mm. Such filaments are processable with a conventional FFF 3D printer. No modifications of the 3D printer are necessary. Detailed mechanical and magnetic investigations of printed samples are performed and discussed. In the presence of an external alignment field, the Sr ferrite particles inside the PA12 matrix can be aligned along an external magnetic field. The remanence can be increased by 40% by printing anisotropic structures. For the 55 vol. % filled filament, a remanence of 212.8 mT and a coercivity of 307.4 mT are measured. The capabilities of printing magnetic anisotropic structures in a complex external field are presented with a Halbach-array arrangement. With the aim of an inverse field model, based on a finite element method, the orientation of the particles and the quality of the print can be estimated by a nondestructive method. (C) 2020 Author(s).