Ambient temperatures of almost 700 °C, higher power density: 3D printing opens up completely new areas of application for electric machines. A start-up of the TU Chemnitz wants to market them.
"The engine printed in the Chemnitz University laboratory represents a breakthrough and is also the proof of principle for our technology," says Johannes Rudolph, who was instrumental in developing the process. The electrical engineers at Chemnitz Technical University simultaneously processed copper, ceramics, and iron on a 3D printer for the first time and thereby produced an electric motor. These motors exhibit power densities that were not achievable with conventional electric motors previously and additionally can operate at much higher ambient temperatures. The researchers succeeded in doing this with the use of metallic and ceramic pastes, which are formed layer-by-layer using an extrusion process and then sintered.
"For the first time, we will present this novelty at the Hanover Fair 2018", says Prof. Dr. Ralf Werner, Professor of Electrical Energy Conversion Systems and Drives at the Technical University of Chemnitz. His scientific colleagues Johannes Rudolph and Fabian Lorenz had already presented a 3D-printed coil last year, which can withstand temperatures of over 300°C. In the meantime, they have succeeded in producing all the important components of an electric machine in one printing process using an in-house developed 3D multi-material printing process. These include the electrical conductors made of copper, which - together with iron or alloys containing iron - cause the formation and orientation of the magnetic fields, and the electrical insulation made of ceramic, which insulates the conductors from one another and from the iron parts referred to as magnetic circuit.
"The aim of the two and a half years of work so far has been to significantly increase the limit of the operating temperature of electrical machines," reports Werner. The Chemnitz researchers achieve this by replacing conventional, polymer-based insulation materials with special ceramics that have a much higher temperature resistance. "The permissible winding temperature of conventional insulation systems of a maximum of 220 °C can thus be significantly exceeded. Thereby, the operating temperature of electrical machines is limited only by the ferromagnetic properties of the iron, which remain unchanged up to approximately 700 °C," Rudolph adds.
In addition to the higher temperature resistance, the ceramic insulation material also has a higher thermal conductivity. This means that the Joule heat in the conductors can be removed 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, somewhat reduced electrical conductivity of copper, an increase in efficiency is possible in particular applications by significantly reducing the winding temperature," adds Lorenz.
The basis of the process, which the Chemnitz researchers now want to further develop to market readiness, is the layer-wise extrusion of highly viscous pastes. These contain particles of the desired materials such as iron, copper or ceramics and specially customized binders. In order to achieve the paste dosing precision required for multi-material printing, the scientists work closely together with ViscoTec Pumpen- u. Dosiertechnik in Töging am Inn. Together with Prof. Lorenz, Johannes Rudolf is already preparing to spin off a start-up from the university.