From a technical perspective, it is easy to manufacture strong magnets. Manufacturing a permanent magnet with a specific pre-determined shaped magnetic field is however tricky. Recently however, researchers at TU Wien have managed to produce permanent magnets using a 3D printer for the first time. Magnets with precisely customized magnetic fields and complex forms can now be produced. One application for these type of magnets is magnetic sensors.
Dieter Süss is the Head of the Christian Doppler Advanced Magnetic Sensing and Materials laboratory at TU Wien. He notes that the strength of a magnetic field is not the only factor that is important when manufacturing magnets. Magnetic fields with field lines arranged in a very specific way are often required. One example would be a magnetic field that varies in strength in one direction, but which is relatively constant in another direction.
Magnets with a sophisticated geometric form must be produced to achieve such requirements. Christian Huber, a doctoral student in Süss’ team explains that computers are used to design magnets. Its shape is adjusted until all requirements for its magnetic field are met.
Once the desired geometric shape is known, the problem becomes implementing the design. Using injection molding is one possibility, but the creation of a mold is expensive and time-consuming, making this method impractical for producing small quantities.
Researchers at TU Wien designed a much simpler method – the first-ever 3D printer that can be used to produce magnetic materials. 3D printers have existed for some time, but these normally create plastic structures. The TU Wien 3D magnet printer operates in much the same way. The magnet printer uses specially created filaments of magnetic micro granulate. These are held together by a polymer binding material. The printer uses a nozzle to apply heat to the material point by point in the desired locations. The result is a three-dimensional object composed of roughly 10% plastic and 90% magnetic material.
As the granulate is deployed in an unmagnetized state, the end product of the printing process is not magnetic. The finished article is converted into a permanent magnet by exposing it to a strong external magnetic field.
Süss notes that magnet designs created with a computer can be implemented quickly and precisely. Various magnetic materials, including exceptionally strong neodymium iron boron magnets, can be processed using this method. The size of the magnets range from decimeters to just a few centimeters, with an accuracy of well under a single millimeter.
Apart from being fast and cost-effective, this new process also opens up new possibilities that would not be possible with other techniques. One example is using different materials within a single magnet to create a smooth changeover between strong and weak magnetism. Süss adds that 3D printing has brought a new aspect to magnet design that could previously only be dreamed of. He now plans to test the limits of how far they can go.
The full study was published in the journal Applied Physics Letters.