E-mobility and additive manufacturing - two trendsetting topics in the manufacturing industry, combined in a terrific success story. Together with the GreenTeam Uni Stuttgart, the CERATIZIT Project Engineering Team developed a machining solution for the challenging final machining of the additively manufactured wheel carriers which drive the all-electric racing car of the Swabian Formula Student team to new levels of performance. A success story that is literally moving.
When you think of students, you generally picture lectures, lecture theatres and student life. It is rather unusual for 70 students to take a break from their studies for a whole year, and dedicate themselves solely to the development and construction of an all-electric racing car to participate in the Formula Student competition. But that is exactly what the members of the GreenTeam Uni Stuttgart have been doing. Since 2009, the team has been among the top 10 in the world and has already broken the world record for acceleration from 0 to 100 kph twice. That leaves even hypercars like a Porsche 918 Spyder behind. Strictly speaking, there are two cars that the annually reconstituted teams have been working on since 2016: a conventional model with a driver, and a driverless vehicle that races with all kinds of sensors and artificial intelligence without direct human intervention.
For the 2021 season, the team had again set its sights on staying well ahead of its competitors with the new E0711-11 EVO model. ‘We are one of the best teams, which is why winning means everything to us,’ explains Maximilian Ziegler, who is responsible for the overall vehicle management mechanics as well as the development of the new wheel carriers. According to Ziegler, the new additively manufactured wheel carriers played a key role in the project: ‘With the new wheel carriers, the car has great potential. Moving the electric motors into the wheels improves the aerodynamics.’
As advanced as the new wheel carriers are, their production is equally complex. ‘The wheel carriers are a very complex component, and we needed the knowledge and experience of industrial specialists to produce them,’ says Ziegler. Working in conjunction with Renishaw, the first step was to optimise the components for additive manufacturing.
But the team soon faced the next challenge, as Ziegler explains: ‘After 3D printing by Renishaw, we needed a solution to machine some surfaces.’ But the search was far from easy. No one dared to take on the challenge of a complex component with diameters over 120 mm, thin walls and tight tolerances on the inner and outer surfaces that had to be machined.
After intensive research, Max Ziegler finally contacted CERATIZIT. Complex machining solutions for customers from the automotive sector, which have to meet the highest demands in terms of performance, precision and process reliability, are part of the daily business of CERATIZIT'S Global Project Engineering Team. Project Manager Tim Haudeck accepted the challenge. ‘We are constantly confronted with the limits of what is possible and are always looking for solutions to push these limits, to make the previously impossible possible after all. Due to the complexity of the processing, the GreenTeam project offered us an ideal opportunity to prove our expertise in the field of e-mobility,’ says Haudeck.
Working in conjunction with the GreenTeam and Renishaw, a detailed analysis of the components and the requirements for 3D printing and post-processing was carried out in order to optimise the wheel carriers and find an optimal machining solution. ‘It quickly became clear to us that we would hardly be able to meet the required tolerances with a standard solution,’ explains Tim Haudeck.
But even with a custom solution, the requirements were high. ‘In order to machine the component on a 5-axis machine with HSK63 interface, we had to reduce the imbalance and minimise the weight to achieve the required tolerances. We soon realised that an optimal result could only be achieved with an additively manufactured solution,’ Haudeck continues. It was not only diameters of over 120 mm that had to be machined. In addition, there were wall thicknesses of sometimes less than 1 mm and IT6 tolerances on both the inner and outer surfaces.
In order to meet the tolerances, all important diameters and fits had to be machined in one clamping procedure. For this purpose, the engineering team designed an additively manufactured special tool with two pocket seats for the indexable inserts and a vibration damper mounted on a U-axis. The lightweight, FEM-optimised design effectively absorbs the forces that occur during machining and allows the machining to be carried out in a single clamping procedure. In addition, additive manufacturing made it possible to deliver the coolant directly to the cutting edge.
Accompanying the development process, and following the machining of his own component, was also a great experience for Maximilian Ziegler: ‘The work with CERATIZIT and Renishaw was fantastic, as we communicated at eye level and share the same passion,’ Ziegler commented enthusiastically after the completion of the first component.
The time and effort spent on the additively manufactured wheel carriers has paid off for the team. In four races during the 2021 season, the GreenTeam finished outright first twice and second once. ‘The car is everything we could have dreamed of. But for me personally, the cooperation with CERATIZIT was also fantastic, it worked out perfectly,’ says Maximilian Ziegler, who could not be happier about the outcome of the season.
For Tim Haudeck the GreenTeam project is a good example of what modern production processes and the expertise of the CERATIZIT employees can achieve. ‘A few years ago it would not have been possible to produce parts like the wheel carrier for the GreenTeam. Only additive manufacturing has made such parts feasible. The prerequisite, of course, is that the necessary expertise regarding applications and tools is available, along with a well developed talent for finding solutions. With our experience in the areas of automotive and e-Mobility and our Global Project Engineering Team, we are ideally positioned to meet the requirements of the automotive industry.’