How Porsche Printed its First-ever E-Drive Housing for Electric Sports Cars
For the first time ever, Porsche has produced the complete housing of an e-drive using 3D printing. The motor-gearbox unit was produced using an additive laser-melting process — and, thanks to its quality and reliability, could be powering electric supercars in the future. Find out how the engineers in Porsche’s legendary development center at Weissach achieved this.
Lighter, more rigid: Porsche has produced its first complete housing for an electric drive using 3D printing. The engine-gearbox unit, which was produced using an additive laser fusion process, passed all the quality and stress tests without any problems.
The additively manufactured alloy housing is more lightweight than a conventionally cast part and reduces the overall weight of the drive by approximately ten percent. Thanks to special structures that can only be produced with 3D printing, stiffness in highly stressed areas has doubled. Another advantage of additive manufacturing is the fact that numerous functions and parts can be integrated. This considerably reduces assembly work and directly improves the quality of parts.
The goal of the engineering team: testing the limits of a new way to manufacture car parts
When two engineers from Weissach started the project, their goal was to test the limits of current software as well as additive manufacturing — and to take away experience from the development for the entire research and development team. After all, 3D printing opens a lot of new opportunities in the development and manufacturing of low-volume parts.
Porsche is intensively driving forward the use of additive manufacturing to optimize highly stressed parts. A few months ago, newly printed pistons successfully proved themselves in the 911 GT2 RS high-performance sports car. The housing for a complete electric drive now also meets high-quality requirements. The downstream two-speed gearbox is integrated into the same housing as the electric motor. This highly integrated approach is designed for potential use on the front axle of a sports car.
No other manufacturing process offers as many possibilities and such fast implementation as 3D printing. Design data can be fed to the printer directly from the computer without any intermediate steps such as tool making. The parts are then created layer by layer from aluminium alloy powder. This makes it possible to manufacture shapes such as housings with integrated cooling ducts and almost any geometry. Every layer is melted and then fused with the previous layer. A few different technologies are available for this purpose. The drive housing was manufactured from high-purity metal powder using the laser metal fusion process (LMF). Here, a laser beam heats and melts the powder surface corresponding to the part contour.
The freedom of 3D design comes at the price of very specific design requirements
Optimization of the electric drive started with the design integration of components such as bearings, heat exchangers and oil supply. This was followed by the computer-calculated definition of loads and interfaces. The load paths were then determined based on this information. The next step of the virtual development method was the optimization of the load paths by integrating the so-called lattice structures. These structures are inspired by nature and can also be seen in similar form in bones or plants, for example.
However, the extended design freedom offered by 3D printing also goes together with specific design requirements. For example, engineers must consider the fact that the workpieces are produced layer by layer by fusion. If there are large protrusions in the shape, supporting elements such as ribs may have to be considered. However, these must not extend into media-carrying ducts. It is therefore important to consider the direction in which the layers are built up as early as the design phase. With the machine technology currently available, printing the first housing prototype took several days and had to take place in two build processes due to the size of the component. With the latest machine generations, it is possible to reduce this time by 90 percent and manufacture the entire housing in one build process.
The weight of the housing parts was reduced by approximately 40 percent by integrating functions and optimizing the topology. This translates to a weight saving of around ten percent for the entire drive due to the lightweight construction. At the same time, stiffness was increased significantly. Despite a continuous wall thickness of only 1.5 millimeters, stiffness between the electric motor and the gearbox was increased by 100 percent due to the lattice structures. The honeycomb structure reduces oscillations in the thin housing walls and thus considerably improves the acoustics of the drive as a whole.
Additive manufacturing offers great potential
The integration of parts made the drive significantly improved the drive package, and reduced the assembly work by around 40 work steps. This is equivalent to a reduction in the production time of approximately 20 minutes. As an additional benefit, the integration of the gearbox heat exchanger with optimized heat transmission improves the cooling of the drive. This is a basic requirement for further increases in performance.
Over the course of the year, from concept to production, all experts involved — including housing designers, topology optimizers, simulation engineers, manufacturing specialists — were able to gain valuable experience that will benefit future developments at Weissach. The housing produced using the 3D printing process again shows the potential of additive manufacturing for Porsche when it comes to product innovation in the future. It has also highlighted the potential in the areas of process innovation — agile development and flexible production — and for new areas of business such as customization, with new offers for customers and spare parts. This manufacturing technology is technically and economically interesting for Porsche, specifically for special and small series, as well as motorsports.
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