Polymer-bonded anisotropic SrFe$_\text{12}$O$_\text{19}$ filaments for fused filament fabrication

TL;DR

This paper presents the development of polymer-bonded anisotropic SrFe12O19 filaments for fused filament fabrication, enabling magnetic anisotropic structures with enhanced remanence, using a process compatible with standard 3D printers.

Contribution

It introduces a new process for producing highly filled, anisotropic magnetic filaments compatible with conventional FFF 3D printers, and demonstrates their magnetic properties and potential applications.

Findings

Remanence increased by 40% with external magnetic field alignment.

Achieved a remanence of 212.8 mT and coercivity of 307.4 mT in printed samples.

Demonstrated printing of magnetic structures using a Halbach-array.

Abstract

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.