Joining processes are essential for production processes along the entire value chain of an electric vehicle. The materials testing institute on the campus of the University of Stuttgart provides a pool of expertise in technologies, tools and processes that combine functional, construction and lightweight materials.
When the established German automotive manufacturers and suppliers are looking for solutions for joining challenges of battery boxes and battery modules, e-axle and e-machine, lightweight body assembly, cell contacting and busbars. They find them at the Materials Testing Institute of the University of Stuttgart.
Change towards lightweight construction and alternative driving systems
The transformation to alternative drive systems brings many changes for the automotive industry. It is not just driving technology and body construction that are changing. Above all, ways are being consistently sought to design vehicles that are light yet safe. Light metals such as aluminum and aluminum alloys are often integrated for this purpose. In many cases, where steel is replaced by other metals, alternative joining processes will be required in the future. Joining processes are essential for production processes along the entire value chain of an electric vehicle.
Green technology for lightweight automotive construction
MPA University of Stuttgart is researching resource-efficient joining processes for the automotive industry. Friction stir welding is a technology with which similar and dissimilar materials can be joined highly efficiently. The welding of aluminum alloys, magnesium or copper for lightweight car body construction is high-strength and more stable than other joining processes. It is conducted at comparatively low temperatures and does not require the addition of gases, consumables or solvents. At the Hannover Messe, Dr. Martin Werz (Materials Testing Institute of the University of Stuttgart) demonstrated a newly developed robot-guided welding gun for the green technology to Baden-Württemberg’s Minister President. This innovation from the Materials Testing Institute has the potential to replace the previously very cost-intensive hardware for friction stir welding. Winfried Kretschmann was extremely impressed by the technology from the Stuttgart-based institute. “Our technology makes cars, and electric vehicles in particular, lighter and safer,” says Dr Martin Werz, Head of the Joining Technology and Additive Manufacturing Department at the Materials Testing Institute at the University of Stuttgart.
Hannover Messe: Baden-Württemberg’s Minister President Winfried Kretschmann listens to Dominik Walz and Dr. Martin Werz (from left). They explain the green technology of friction stir welding and its significance for lightweight construction. Photo: Ralf Hansen, Hannover
In the production of electric vehicles, friction stir welding has essential advantages over processes such as riveting, clinching or MAG/MIG welding. Its advantages lie in the good joinability of aluminium alloys and steel with relatively low energy consumption. The process can be automated, as demonstrated by the MPA University of Stuttgart in a VIP+ development project funded by the German Federal Ministry of Education and Research. The MPA University of Stuttgart presented the prototype of an Industry 4.0 application for the high-strength, resource-efficient joining of car body components at the Hannover Messe in April last. It is a recently developed robot-assisted welding gun for friction stir welding. Dominik Walz, a postgraduate at the department for Joining Technology and Additive Manufacturing at the Materials Testing Institute, is playing a leading role in this development. “The robot-guided friction stir welding gun is the result of interdisciplinary research by experts from the fields of materials, control and systems engineering,” says Dominik Walz. “Through interdisciplinary collaboration between the institutes, we want to bring the technology to application maturity within the project duration,” continues Walz.
This development is of great importance for the lightweight assembly of aluminium and hybrid components. As lightweight car bodies are currently indispensable for vehicles with alternative drive systems, this will also advance electromobility.
Supporting the industry during the transition to electromobility
The German Federal Ministry for Economic Affairs and Climate Protection has set up so-called transformation hubs to support manufacturers and SMEs in the transition to electromobility. At the Materials Testing Institute of the University of Stuttgart, the transformation hub “CyberJoin” processes knowledge concerning joining, manufacturing and materials technology. CyberJoin presents it to suppliers and vehicle manufacturers free of charge via regular conferences and the platform www.cyberjoin.de. The transformation hub brings together managers from industry and managing directors of medium-sized supplier companies with specialists from research and science.
Around 450 participants are already involved 10 months after the start the hub – including well-known vehicle manufacturers (OEMs). They share their experience and knowledge in the production of electric vehicles and thus pave the way for e-mobility. The events of the CyberJoin transformation hub meet the suppliers’ demand. For example, robot-guided welding guns for friction stir welding can be tested on the systems in the MPA laboratory. Both thermal joining processes (such as soldering, welding) and mechanical joining processes (such as clinching, semi-tubular riveting, screwing or gluing) are presented. The challenges of joining in e-mobility are worked out. The speakers include industrial groups and numerous SMEs.
“I think it’s very important for Germany as a centre of commerce and industry that there are hubs like this,” said Anne Dickel during the workshop on March 14th in the laboratory of the Materials Testing Institute (MPA) at the University of Stuttgart. The vehicle technology engineer from EJOT SE & CO. KG reported on direct screw coupling and commented: “The events serve to build a network and support companies in their transformation. Today’s workshop was an unbelievably valuable event. I was very impressed by the range of topics covered in the presentations.”
The CyberJoin transformation hub has a demonstration lab on the campus of the University of Stuttgart to showcase the latest technological developments. The demonstration laboratory currently includes equipment for resistance spot welding, ultrasonic welding, inert gas welding and friction stir welding. Special mention should be made of systems that are being developed in completed or parallel research projects and are also available to CyberJoin participants. For example, the new type of robot-guided welding gun that was shown at the exhibition in Hanover. In addition, additive manufacturing systems are available, in particular a TruPrint 3000 from Trumpf. This demonstration laboratory has grown steadily since July 2023 and is constantly being expanded. Several companies have already donated equipment to the University of Stuttgart for this purpose.
Dr. Martin Werz, Head of the Joining Technology and Additive Manufacturing Department at the Materials Testing Institute is in charge of the Transformation Hub. He coordinates it together with Prof. Dr. Heidi Cramer, Head of Research and Innovation at Gesellschaft für Schweißtechnik International GmbH. Both Werz and Cramer look back on eight successful events at seven locations across Germany with presentations on a wide range of thermal and mechanical joining processes – some using demonstrators brought along, others on the system. Keynote speakers from vehicle manufacturers and original equipment manufacturers (OEMs) such as Mercedes-Benz, BMW and Audi, Tier 1 and system suppliers such as ThyssenKrupp Steel Europe AG, suppliers of components, workpieces, materials and systems such as KUKA Deutschland GmbH, BOSCH Rexroth AG and TRUMPF Laser- und Systemtechnik GmbH actively participate. The speakers include industrial groups and numerous medium-sized companies.
Interest in the exchange via conferences at the Materials Testing Institute of the University of Stuttgart is constantly growing. After all, the production processes and value creation networks in the automotive industry are undergoing major changes in the context of the digitalization of production as well as energy efficiency and resource conservation.
Bettina Mayer, MPA/Transformation hub CyberJoin
