The 3D printing proecss uses metallic and ceramic pastes simultaneously, extruded layer by layer into a predetermined form and then sintered together to produce the motor. Coils are produced by placing the particles of the desired materials, such as iron, copper or ceramics, and specially-adapted bonding agents, in the right place as the monolithic motor is printed, rather than printing separate coils. In order to achieve the necessary degree of precision to build the embedded coils, the researchers worked closely with paste supplier ViscoTec Pumpen- u. Dosiertechnik in Töging am Inn.
“This is the first of its kind in the world,” said Prof. Dr. Ralf Werner, head of the department of Electrical Energy Conversion Systems and Drives. Last year, two members of his team, Johannes Rudolph and Fabian Lorenz, developed a 3D-printed coil capable of withstanding temperatures over 300°C. Since that time, they have successfully printed all the key components, including copper electrical conductors, which create magnetic fields in combination with iron or iron alloys and ceramic electrical insulation, which insulates the conductors from each other and from the iron components.
“Our goal over the last two and a half years was to dramatically increase the temperature that electrical machines are capable of withstanding,” said Werner. This was made possible by replacing conventional polymer-based insulation materials with specialized ceramics that can be 3D printed to provide a much higher degree of temperature resistance. This will lead to smaller, more efficient motors.
“The maximum permissible winding temperature of 220°C associated with conventional insulation systems can then be exceeded by a significant amount. The operating temperature of electric machines is therefore only limited by the ferromagnetic properties of the iron components, which can only be maintained up to 700°C,” said Rudolph.
Along with the ability to withstand higher temperatures, the ceramic insulation material also possesses a higher degree of thermal conductivity so that heat generated in the conductors can be more quickly dissipated. This allowed a higher output power.