Additive Manufacturing of Hard Magnetic Passive Shims to Increase Field Homogeneity of a Halbach Magnet

Abstract

Obtaining a highly homogeneous magnetic field is desired for field‐controlled applications. For example, the resolution of magnetic analysis methods can be improved by generating a stronger and more homogeneous field over the region of interest (ROI). A set of 3D‐printed passive shims is fabricated using additive manufacturing to improve the magnetic field homogeneity of a Halbach magnet assembly. The feedstock is a custom acrylonitrile butadiene styrene (ABS)‐hard magnet composite filament filled with 60% wt. isotropic NdFeB. Additionally, a method for investigating the remanence is developed and validated. The result reveals a good agreement between the new method and existing measurement techniques for the remanence of permanent magnets. It is also shown that the additive manufacturing procedure has negligible effects on the magnetic properties. Performing a parametric study over a rectangular ROI, an optimized shim configuration is achieved. In the optimized and 3D‐printed configuration, the average norm of the magnetic flux density, Bnorm, is increased by 13% and, more importantly, a 43% increase in the magnetic uniformity is obtained. These results highlight the great potential of freeform manufacturing, namely, additive manufacturing, to tailor the properties of magnet structures.

3D Printing Technologies for Fabrication of Magnetic Materials Based on Metal–Polymer Composites: A Review

“…In [58], the use of ATs, in particular, the FDM technology, was studied to improve the Halbach magnetic assembly. The Halbach magnetic assembly is a special configuration of permanent magnets, characterized by the fact that the magnetic field on one of its sides is almost completely absent due to the special arrangement of the assembly elements, and it is homogeneous inside.…”

“…This insert tends to improve the uniformity of the magnetic field in a rather simple Halbach assembly, consisting of only four cubic magnetic blocks. The use of the hard magnetic shimming method with the optimal configuration of the shimming element made it possible to increase the average value of magnetic induction by 13% and, more importantly, to increase the magnetic uniformity in the region of interest by 43% [58].…”

“…To prepare it, single or twin screw extruders are used [71,72]. The production of composite filaments can be carried out by any other manufacturer [41,58] or directly in the FDM printer with the connection of such an extruder to it [48,71,73]. To obtain a uniform distribution of the filler in the filament, various techniques are used.…”

“…The magnetization of each structure is represented by the white arrows. The solid black lines illustrate the dipole magnetic fields obtained within the plane of the Halbach assemblies[58].…”