Polymer-bonded anisotropic SrFe12O19 filaments for fused filament fabrication

Christian Huber,Iulian Teliban,Martin Groenefeld,Santiago Cano,Dieter Suess,Stephan Schuschnigg

doi:10.1063/1.5139493

Abstract

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.

Highlights

Fused filament fabrication (FFF) or fused deposition modeling (FDM) is a well-known and widely used additive manufacturing (3D printing) process that uses a thermoplastic wire-shaped filament to build a workpiece layer-by-layer.1 By mixing magnetic particles with a thermoplastic matrix material, fused filament fabrication (FFF) can be used to print polymer-bonded hard or soft magnets.2–10 Most recent publications about FFF of hard magnetic materials use isotropic NdFeB powder for the filament fabrication
We describe the extrusion process and the properties of polymer-bonded anisotropic SrFe12O19 filaments for fused filament fabrication (FFF)
The remanence can be increased by 40% by printing anisotropic structures

Summary

INTRODUCTION

Fused filament fabrication (FFF) or fused deposition modeling (FDM) is a well-known and widely used additive manufacturing (3D printing) process that uses a thermoplastic wire-shaped filament to build a workpiece layer-by-layer. By mixing magnetic particles with a thermoplastic matrix material, FFF can be used to print polymer-bonded hard or soft magnets. Most recent publications about FFF of hard magnetic materials use isotropic NdFeB powder for the filament fabrication. By mixing magnetic particles with a thermoplastic matrix material, FFF can be used to print polymer-bonded hard or soft magnets.. Most recent publications about FFF of hard magnetic materials use isotropic NdFeB powder for the filament fabrication. NdFeB has the highest maximum energy product (BH)max of all commercially available magnetic materials, but due to the large amount of rare-earth materials, it is one of the most expensive magnets. Another disadvantage is the low working temperature compared to other materials and the negative temperature coefficient of the coercivity.. Magnetic fields larger than 1.2 T are necessary to align anisotropic NdFeB powder particles inside a plasticized thermoplastic matrix.. Structures with a complex magnetization distribution are printed and characterized by an inverse field computational model

FILAMENT EXTRUSION

MATERIAL CHARACTERIZATION

INVERSE FIELD MODELING

Findings

CONCLUSION