3-D-printed permanent magnets outperform conventional versions, conserve rare materials

November 1, 2016 by Stephanie G. Seay
This isotropic, neodymium-iron-boron bonded permanent magnet was 3-D-printed at DOE's Manufacturing Demonstration Facility at Oak Ridge National Laboratory. Credit: Oak Ridge National Laboratory

Researchers at the Department of Energy's Oak Ridge National Laboratory have demonstrated that permanent magnets produced by additive manufacturing can outperform bonded magnets made using traditional techniques while conserving critical materials.

Scientists fabricated isotropic, near-net-shape, neodymium-iron-boron (NdFeB) bonded magnets at DOE's Manufacturing Demonstration Facility at ORNL using the Big Area Additive Manufacturing (BAAM) machine. The result, published in Scientific Reports, was a product with comparable or better magnetic, mechanical, and microstructural properties than bonded magnets made using traditional injection molding with the same composition.

The additive manufacturing process began with composite pellets consisting of 65 volume percent isotropic NdFeB powder and 35 percent polyamide (Nylon-12) manufactured by Magnet Applications, Inc. The pellets were melted, compounded, and extruded layer-by-layer by BAAM into desired forms.

While conventional sintered magnet manufacturing may result in material waste of as much as 30 to 50 percent, additive manufacturing will simply capture and reuse those materials with nearly zero waste, said Parans Paranthaman, principal investigator and a group leader in ORNL's Chemical Sciences Division. The project was funded by DOE's Critical Materials Institute (CMI).

Composite pellets are melted, compounded, and extruded layer-by-layer into desired forms. Credit: Oak Ridge National Laboratory

Using a process that conserves material is especially important in the manufacture of made with neodymium, dysprosium—rare earth elements that are mined and separated outside the United States. NdFeB magnets are the most powerful on earth, and used in everything from computer hard drives and head phones to clean energy technologies such as electric vehicles and wind turbines.

The printing process not only conserves materials but also produces complex shapes, requires no tooling and is faster than traditional injection methods, potentially resulting in a much more economic manufacturing process, Paranthaman said.

"Manufacturing is changing rapidly, and a customer may need 50 different designs for the magnets they want to use," said ORNL researcher and co-author Ling Li. Traditional injection molding would require the expense of creating a new mold and tooling for each, but with additive manufacturing the forms can be crafted simply and quickly using computer-assisted design, she explained.

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Credit: Oak Ridge National Laboratory

Future work will explore the printing of anisotropic, or directional, bonded magnets, which are stronger than isotropic magnets that have no preferred magnetization direction. Researchers will also examine the effect of binder type, the loading fraction of magnetic powder, and processing temperature on the magnetic and mechanical properties of printed magnets.

Alex King, Director of the Critical Materials Institute, thinks that this research has tremendous potential. "The ability to print high-strength magnets in complex shapes is a game changer for the design of efficient electric motors and generators," he said. "It removes many of the restrictions imposed by today's manufacturing methods."

"This work has demonstrated the potential of to be applied to the fabrication of a wide range of magnetic materials and assemblies," said co-author John Ormerod. "Magnet Applications and many of our customers are excited to explore the commercial impact of this technology in the near future," he stated.

Explore further: For the first time, magnets are be made with a 3-D printer

More information: Ling Li et al, Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets, Scientific Reports (2016). DOI: 10.1038/srep36212

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Eikka
not rated yet Nov 01, 2016
Considering the material is magnetic to start with, could you effectively print over nothing by applying a suitable magnetic field to cancel gravity?

Saves the use of support material with overhangs.
optical
Nov 01, 2016
This comment has been removed by a moderator.
optical
Nov 01, 2016
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Gigel
5 / 5 (1) Nov 02, 2016
Considering the material is magnetic to start with, could you effectively print over nothing by applying a suitable magnetic field to cancel gravity?

Saves the use of support material with overhangs.

That would make printing more complicated and there would still be some support material to print the first layer on. The powder is essentially a fluid so it won't stay mid-air.
optical
Nov 02, 2016
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antialias_physorg
not rated yet Nov 02, 2016
The powder is essentially a fluid so it won't stay mid-air.

Yeah. This would require to adjust the magnetic base field on the fly during printing to account for the already printed material (by weight, distribution and its own magnetic field) as well as that coming out of the nozzle to keep this stuff from flying everywhere. If you've ever played around with magnets you'll know that this is extremely difficult.

It would take some serious fast and micrometer level capability (not to mention that the carrying power of such a non-contact bed would severely limit the size of stuff you could print.)
At some magnetic field strength - with the constant adjustments needed - you'd run into all sorts of problems with induced currents in your printed material, electronics, ... )

If you really want to print while levitating then do so in space where you have zero (or micro) gravity
fidh
not rated yet Nov 03, 2016
@antialias, while difficult and limiting for mass production, it could enable printing of impossible assemblies. Like a magnetic sphere inside a magnetic sphere with no support material to hinder it's performance (whatever that could be) once finished.
I.e., it could be a viable way to produce limited quantity components for highly specialized purposes.
antialias_physorg
not rated yet Nov 03, 2016
Like a magnetic sphere inside a magnetic sphere

That would be an extremely unstable thing to print (in any case the outer shell would shield the magnetic field of your base and there'd be no way you'd get the inner sphere/material to float during printing.

There are already ways tp print such structures with very limited support structures (or even without if you include a small hole and a sacrificial material) e.g. like here:
http://www.123dap.../3938598
fidh
not rated yet Nov 04, 2016
@antialias,
Do you mean it's impossible to get the inner material floating even with a pentagon sized electromagnet assembly handling the 'floatage'?
Like I said before, with enough effort it would offer the choice to create something that we aren't capable of producing. I.e. a completely solid magnetic outer sphere and another equally solid magnetic inner sphere.
Just saying it makes something that was impossible, possible.
For what purpose? Not the slightest clue.
Eikka
not rated yet Nov 06, 2016
The powder is essentially a fluid so it won't stay mid-air.


It's not a powder. The powder is suspended in a thermoplastic that is extruded out of an ordinary 3D printer - read the article.

Such printers can already print overhangs because the material solidifies as it cools down. The amount of free overhang is limited by the cooling rate and the sagging of the material under its own weight, which then requires supports to be printed in, which waste material and require extra work to remove.

If the material is magnetic, you can essentially "cancel" gravity by an external field, which then enables you to make longer overhangs and bridges without printing in supports, which enables more complex geometries.

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