Automotive supplier and international development partner MAHLE has produced high-performance aluminium pistons using 3D printing techniques as part of a cooperation between Porsche and mechanical engineering company Trumpf. The pistons were also tested on the engine test bench for Porsche 911 GT2 RS. MAHLE states that while forged pistons have reached their potential limits, 3D printed pistons could boost the 700 hp Porsche engine by 30 hp and also improve efficiency. MAHLE is taking forward its expertise in 3D printing so as to also work in the field of alternative drives like electric by supplying customers with components for drives, thermal management, and mechatronics.
Benefits of 3D printed pistons
The process makes use of bionic design that mimics natural structures such as the human skeleton and the material is added only in loaded areas, so the structure of the piston is adapted to the load. Saving material, the process has the potential to save on weight by up to 20 percent.
MAHLE also used a specially shaped cooling gallery near the piston rings applying its expertise with thermal processes on the piston. The cooling gallery is only possible with 3D printing. These reduce temperatures at the top land, which undergoes a lot of stress, thus optimizing combustion and allowing higher maximum engine speeds.
The pistons use a special aluminium alloy developed by MAHLE and is atomized into a fine powder before being printed in a process known as laser metal fusion (LMF). The laser melts the powder to certain layer thickness, followed by a new layer on top, hence printing the piston 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.
Quality test run
Besides cutting open pistons for analysis, project partner Zeiss carried out a number of non-destructive tests like CT scanning, 3D scanning, and microscopy. Zeiss confirms that the printed piston has the same high-quality standard as a conventionally manufactured production piston.
For practical testing, a Porsche 911 GT2 RS engine was fitted with six pistons, and the drive unit successfully completed 200 hours of endurance testing under the toughest conditions on the test bench.
The test comprised of around 6,000 km at an average speed of 250 km/h including refueling stops, and around 135 hours at full load. The run also had included 25 hours of motoring load, which is the simulated overrun mode of a vehicle.
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