MAHLE, working together with sports car manufacturer Porsche and mechanical engineering company Trumpf, has manufactured high-performance aluminium pistons using 3D printing techniques for the first time. The pistons were successfully tested on the engine test bench for Porsche’s 911 GT2 RS sports car.
The standard forged pistons have reached the limits of their performance potential; it is feasible that the power of the 700hp Porsche engine could be boosted by 30hp with an associated increase inefficiency.
MAHLE said: “It is specifically developing its expertise in 3D printing, so that, in the future, it will also be able to support its customers in the field of alternative drives, including electric drives, by supplying suitable components for drives, thermal management, and mechatronics promptly.”
Dr Martin Berger, Head of Corporate Research and Advanced Engineering at MAHLE, said: “The results of the project confirm the great potential of 3D printing and demonstrate MAHLE’s particular competence in the field of high-performance small and limited runs and relation to prototyping and aftermarket.”
Frank Ickinger, Project Manager at Porsche, commented: “Thanks to the close cooperation of everyone involved, we were able to demonstrate the potential of additive manufacturing in our top-of-the-line high-performance sports car, the Porsche 911 GT2 RS, thus clearing the way for its use in future drives. In terms of technology, this is the start of a new chapter for us, which opens up completely new possibilities in design and production.”
Steffen Rubling, Project Manager at Trumpf, also sees big opportunities for 3D printing in future manufacturing processes. “The project illustrates how 3D printing can be used to further improve components whose performance potential has already been exhausted by decades of development. This will benefit many other industries, such as aerospace and energy.”
The new process presents the option of implementing a so-called bionic design. It saves material and has the potential to make the 3D printed piston up to 20% lighter than its conventionally manufactured counterpart while increasing rigidity.
Moreover, the designers at MAHLE have instituted an immaculately positioned and specially shaped cooling gallery near the piston rings. This design is based on MAHLE’s many years of experience with thermal processes on the piston and is only possible using 3D printing. The cooling gallery reduces the temperature load at the so-called top land, a particularly stressed part of the piston, thus optimizing combustion and paving the way for higher maximum engine speeds.
The new production process is based on a special Aluminum alloy developed by MAHLE with a long history of successful use in cast pistons. The alloy is atomised into a fine powder and then printed in a process known as laser metal fusion (LMF). A laser beam melts the powder to the desired layer thickness, followed by the application of a new layer on top, thereby building the piston up one layer at a time. Using this method, 3D printing specialist Trumpf produces piston blanks made up of approximately 1,200 layers in around 12 hours.
The piston blank is then finished, measured, and tested at MAHLE and must meet the same strict standards as a conventionally manufactured part.
In addition to cutting open pistons for analysis, project partner Zeiss carried out numerous non-destructive tests using procedures including CT scanning, 3D scanning, and microscopy.
The results show that the printed piston achieves the same high-quality standard as a conventionally manufactured production piston. When it came to practical testing, six pistons were fitted in the engine of the Porsche 911 GT2 RS, and the drive unit completed 200 hours of endurance testing under the toughest conditions on the test bench. This comprised around 6,000 kilometres at an average speed of 250 km/h including refuelling stops, and around 135 hours at full load. The test run also included 25 hours of motoring load, i.e., the simulated overrun mode of a vehicle.
Further evidence of the advantages of 3D printing is provided by an additional charge air cooler, again developed as part of the joint project with Porsche and Trumpf.
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