AM Permanent Magnets for Electric Motors
Researchers Fabrice Bernier and Jean-Michel Lamarre at the National Research Council of Canada (NRC) have developed a method to produce permanent magnets for electric motors via cold spray metal additive manufacturing (AM).
Currently, high-performance magnets used in electric motors are typically made using processes such as powder compaction for sintered magnets or injection molding for bonded magnets. In these processes, magnets must first be fabricated and then shaped and assembled into a final product. The NRC's cold spray technology combines these steps into one. This new technology not only leads to significant cost reductions, but also opens a world of design possibilities that were inconceivable with the traditional manufacturing processes.
Cold spray AM is a process where a material in fine powder form is accelerated in a high-velocity compressed gas jet. A stream of powder impacts a target at great speed where it starts building up layer upon layer. To control the process, an industrial robot is used to perform rapid and precise 3D movements, allowing the creation of complex shapes. In comparison to other additive manufacturing technologies, the cold spray technique has the advantage of very high buildup rates that allow the production of several kilograms of magnets per hour.
The NRC states that another advantage to cold sprayed magnets is that they have excellent mechanical and thermal properties. The high velocities used in the deposition of the material and the absence of polymer in the material matrix combine to give the magnet intrinsic mechanical properties that are far superior to conventional magnets. The adhesion of the magnetic material to the surface of the part is exceptional, since neither glue nor assembly is used. Magnets created using cold spray additive manufacturing are easy to machine when compared to the more brittle sintered magnets. The NRC technology also offers magnets with increased thermal conductivity which allows for better temperature control. These magnets are corrosion and oxidation resistant and will therefore have a longer lifespan.
Prototypes using this new hard magnetic material have been constructed and tested with success. The NRC's researchers are already looking into new ways to use cold spray AM to enhance motor designs. They are actively working on the development of soft magnetic materials to complete the range of available resources. According to Fabrice Bernier: "this technology will allow the creation of more compact, better performing motors for the future and could pave the way for building entire motors using cold spray technology, offering significant advantages such as cost reduction, better thermal management and more complex geometries and functionalities."