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Selective laser sintering of bonded anisotropic permanent magnets using an in situ alignment fixture

Martin Christopher Mapley (School of Engineering, Griffith University, Brisbane, Australia and Innovative Cardiovascular Engineering and Technology Laboratory, Prince Charles Hospital, Chermside, Australia)
Geoff Tansley (Faculty of Science Environment Engineering and Technology, School of Engineering and Built Environment, Griffith University Southport, Australia, and Innovative Cardiovascular Engineering and Technology Laboratory, Prince Charles Hospital, Chermside, Australia)
Jo P. Pauls (School of Engineering, Griffith University, Brisbane, Australia and Innovative Cardiovascular Engineering and Technology Laboratory, Prince Charles Hospital, Chermside, Australia)
Shaun D. Gregory (Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Australia)
Andrew Busch (School of Engineering and Built Environment, Griffith University, Brisbane, Australia)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 29 March 2021

Issue publication date: 4 June 2021

137

Abstract

Purpose

Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via several AM techniques to allow for rapid manufacture of complex geometries. These magnets, however, tend to suffer from lower residual induction than the industry standard of injection moulding primarily due to the lower packing density of the magnetic particles and secondly due to the feedstock consisting of neodymium-iron-boron (Nd-Fe-B) powder with isotropic magnetic properties. As there is no compaction during most AM processes, increasing the packing density is very difficult and therefore the purpose of this study was to increase the magnetic properties of the PMs without increasing the part density.

Design/methodology/approach

Accordingly, this research investigates the use of anisotropic NdFeB feedstock coupled with an in-situ alignment fixture into an AM process known as selective laser sintering (SLS) to increase the magnetic properties of AM magnets. A Helmholtz coil array was added to an SLS machine and used to expose each powder layer during part fabrication to a near-uniform magnetic field of 20.4 mT prior to consolidation by the laser.

Findings

Permeagraph measurements of the parts showed that the alignment field introduced residual induction anisotropy of up to 46.4 ± 2.2% when measured in directions parallel and perpendicular to the alignment field. X-ray diffraction measurements also demonstrated a convergence of the orientation of the crystals when the magnets were processed in the presence of the alignment field.

Originality/value

A novel active alignment fixture for SLS was introduced and was experimentally shown to induce anisotropy in bonded PMs. Thus demonstrating a new method for the enhancement in energy density of PMs produced via AM methods.

Keywords

Acknowledgements

This work was supported by the Prince Charles Hospital Foundation, Brisbane, Australia [NI2017-28, TM2017-04]. Jo P. Pauls was supported by a Fellowship (RF2018-04) from The Prince Charles Hospital Foundation, Brisbane, Australia. Shaun D. Gregory was supported by a Fellowship (102062) from the National Heart Foundation of Australia. .

Citation

Mapley, M.C., Tansley, G., Pauls, J.P., Gregory, S.D. and Busch, A. (2021), "Selective laser sintering of bonded anisotropic permanent magnets using an in situ alignment fixture", Rapid Prototyping Journal, Vol. 27 No. 4, pp. 735-740. https://doi.org/10.1108/RPJ-09-2020-0220

Publisher

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Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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