In the 3D printing process at Chemnitz University of Technology, metallic and ceramic pastes are shaped layer by layer using an extrusion process and then sintered. Last year, research assistants Johannes Rudolph and Fabian Lorenz presented a 3D-printed coil that can withstand temperatures of over 300°C. They have now succeeded in doing so with their self-developed 3D multi-material coil. They have now succeeded in producing all the important components of an electrical machine in a single printing process using the 3D multi-material printing process they developed themselves. These include the electrical conductors made of copper, which together with iron or iron-containing alloys cause the formation and alignment of the magnetic fields, and the electrical insulation made of ceramic, which insulates the conductors from each other and from the iron parts known as the magnetic circuit.

"The aim of the work, which has taken around two and a half years, has so far been to significantly raise the limit of the operating temperature of electrical machines," reports Prof. Dr. Ralf Werner, holder of the professorship. The Chemnitz researchers have achieved this by replacing conventional, polymer-based insulation materials with special ceramics that have a much higher temperature resistance. "The maximum permissible winding temperature of conventional insulation systems of 220 °C can therefore be significantly exceeded, which means that the operating temperature of electrical machines is only limited by the ferromagnetic properties of the iron, which remain up to around 700 °C," adds Rudolph.

Higher thermal conductivity

In addition to the higher temperature resistance, the ceramic insulation material also has a higher thermal conductivity. This means that the heat loss generated in the conductors can be dissipated more quickly. In this way, the scientists achieve another important goal of their work: increasing the power density of electrical machines. "Despite a process-related, slightly reduced electrical conductivity of the copper, it is also possible to increase efficiency in special applications by significantly reducing the winding temperature," adds Lorenz.

The basis of the process, which the Chemnitz researchers now want to develop to market maturity, is the layer-by-layer extrusion of highly viscous pastes. These contain particles of the desired materials such as iron, copper or ceramics and specially tailored binders. The scientists are working closely with ViscoTec Pumpen- u. Dosiertechnik in Töging am Inn to achieve the precision required for multi-material printing when dosing the pastes.

"The motor printed in the Chemnitz university laboratory represents a breakthrough and is also proof of the feasibility of our technology," assures Rudolph, who played a key role in developing the process and is preparing a spin-off from the university together with Lorenz. The scientists will be presenting the current status of their research at the Hannover Messe from April 23 to 27, 2018 at the joint stand "Research for the Future" in Hall 2, Stand A38. There, Rudolph and Lorenz hope to attract further interested parties to their new 3D multi-material printing process.