  In this publication we describe the extrusion process and the properties of
polymer-bonded anisotropic SrFe$_\text{12}$O$_\text{19}$ 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. By 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.
