3-D printers offer better way to make some magnets

New method conserves expensive materials
Dec 13, 2016 — 7:00 am EST
printed magnet

This magnet was created on a 3-D printer at Oak Ridge National Laboratory in Tennessee. (A ruler is shown for scale.) The method wastes less material than other ways of making magnets.

Oak Ridge National Laboratory

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

Powerful magnets are all around you. They’re found in electronic devices, ranging from speakers to the hard drives of computers. They’re also key to the many motors that keep an elevator or car working. They're almost everywhere and in high demand. So scientists and engineers are chasing ways to improve them. And now a group of researchers have found a novel way. They build them with 3-D printers.

The magnets in all of these devices aren’t like the ones that you use to stick art on the fridge. These magnets are made of "rare earths." These are a group of similar metallic elements that tend to be difficult to find and to mine in large quantities. That makes them expensive. So scientists would like to find ways to use these elements more efficiently.

Parans Paranthaman is a materials scientist at Oak Ridge National Laboratory in Tennessee. His group figured out a way to make strong magnets in any size or shape. These researchers used additive manufacturing. It's a type of 3-D printing, where a machine “prints” a solid object by building it layer by layer, from the bottom up.

New devices — in everything from cars to cell phones — often need custom-shaped magnets, notes Paranthaman. One advantage of 3-D printing is that it lets people customize magnets to fit any project. 

This type of manufacturing “gives you the ability to make these magnets in more complex shapes than are possible with conventional machining,” says Randy Bowman. He studies magnets at NASA's Glenn Research Center in Cleveland, Ohio, and was not part of the new study. (NASA stands for the National Aeronautics and Space Administration.)

Paranthaman and his team printed “bonded” magnets. That means they contain magnetic powders held together with a polymer, molecules made from long chains of identical molecules. (A polymer tends to be plastic, resin or related material.) Combining some magnetic material with a polymer means bonded magnets don't break as easily as pure magnets.

Bonded magnets usually are made with a technique known as injection molding. That process involves heating the magnetic material until it's liquid, then forcing it into a mold. When the liquid cools, it solidifies into the right shape. Injection molding is useful for making lots and lots of magnets that all have the same shape. But it’s not so great for making just a few magnets. That's because it takes time, money and materials to build a single mold, even before the first magnet is made. Building the mold for an injection-created produce to make just a single magnet would be like building a photocopying machine to copy just one sheet of paper.

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Magnets made with a 3-D printer conserve rare materials and outperform conventional magnets.
Oak Ridge National Laboratory

Permanent magnets also can be made through a process called sintering. Here, the metal particles are heated and squished together until they stick. This produces a slab of magnet, which later must be cut and grinded into the desired shape. Paranthaman says sintering can waste as much as half of the raw material.

3-D printing, however, is good for small batches. The process lets inventors print magnets and test them. These tests help them find the best magnet design before going to the trouble and effort of building a mold. 3-D printing also may be useful to companies that only want to make a small number of magnets. And because 3-D printing directly forms the material into the shape of the magnet, it produces little waste. That's important, in part, because the ingredients in bonded magnets tend to be so expensive.

Bowman says scientists are searching for ways to make less costly magnets. To do that here, they must use less of the magnet’s very expensive raw ingredients. And with 3-D printing, he says, “there tends to be less scrap.”

To nail down the 3-D-printing process, Paranthaman and his group took two years of trial and error. But their work paid off. They now they have a working recipe.

Their magnet-making process starts with magnetic pellets. These contain the elements iron, boron and neodymium (Nee-oh-DIM-ee-um) in powder form. Neodymium is a soft metal. It is also a rare earth. The pellets contain nylon, too. During the printing process, the machine heats the pellets, which melt into a liquid. That liquid passes through a nozzle called an extruder. It moves back and forth and right and left. As it does, the nozzle deposits each layer of the material at the proper spot to make the right shape. Once it finishes one layer, the nozzle starts to make another layer atop it.

Challenges still remain in printing magnets for real-world use. One big challenge is temperature. At the high temperatures at which a motor runs, for example, the magnetic field starts to weaken, Paranthaman notes.  So his goal is to design a strong magnet that works well, even at high heat. 

Power Words

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3-D printing     A means of producing physical items — including toys, foods and even body parts — using a machine that takes instructions from a computer program. That program tells the machine how and where to lay down successive layers of some raw material (the “ink”) to create a three-dimensional object.

additive manufacturing     This process of creating solid objects by depositing material, micro-layer by micro-layer (or slice by slice) from the bottom up. It’s an explanation for how 3-D printing works.

boron     The chemical element having the atomic number 5. Its scientific symbol is B.

element     (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

extract     (v.) To separate one chemical (or component of something) from a complex mix. (noun) A substance, often in concentrated form, that has been removed from its natural source. Extracts are often taken from plants (such as spearmint or lavender), flowers and buds (such as roses and cloves), fruit (such as lemons and oranges) or seeds and nuts (such as almonds and pistachios). Such extracts, sometimes used in cooking, often have very strong scents or flavors.

hard drive     A device that reads and writes — and hence can store — digital data onto a rigid magnetic disk.

iron     A metallic element which is common in minerals of the Earth’s crust and in its hot core. This metal is also found in cosmic dust, and in many meteorites that fall to Earth from space.

liquid     A material that flows freely but keeps a constant volume, like water or oil.

magnet     A material that usually contains iron and whose atoms are arranged so they attract certain metals.

magnetic field     An area of influence created by certain materials, called magnets, or by the movement of electric charges.

manufacturing     The making of things, usually on a large scale.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

motor     A device that converts electricity into mechanical motion.

NASA     Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It has also sent research craft to study planets and other celestial objects in our solar system.

neodymium     A chemical element which appears as a soft, silvery metal when it is pure. It is found in some minerals, and can be used to trace the source of mineral grains carried long distances by water or wind. Its scientific symbol is Nd.

nozzle     A round spout or slot at the end of a pipe, hose or tube. Nozzles are typically used to control the flow of a jet of high-pressure liquid or gas.

nylon     A silky material that is made from long, manufactured molecules called polymers. These are long chains of atoms linked together.

particle     A minute amount of something.

plastic     Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.

polymer     A substance made from long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).

rare earths     (in Earth science) These are a group of metal elements that tend to be soft, bendable and chemically reactive.

resin     A sticky, sometimes aromatic substance, often secreted by plants. It may also be the viscous starting ingredient for some plastics that will harden when heated or treated with light.

sintering     Using heat to turn a powdered material into a solid.

solid     Firm and stable in shape; not liquid or gaseous.

waste     Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.


Journal: L. Li et al. Big area additive manufacturing of high performance bonded NdFeB magnets. Scientific Reports. Published online Oct. 31, 2016. doi: 10.1038/srep36212.