As part of the cooperation with the sports car manufacturer Porsche and the machinery manufacturing company Trumpf, the German auto parts manufacturer MAHLE used 3D printing technology to produce high-performance aluminum pistons for the first time. The 911 GT2 RS sports car passed the test on the engine test bench. Although standard forging pistons have reached the limit of their performance potential, it is still possible to increase the power of the Porsche 700 HP engine by 30 HP by improving its efficiency. MAHLE is developing its 3D printing technology. In the future, the company will be able to support customers in the field of alternative drive systems such as motors by providing suitable components for drive systems, thermal management and mechatronics systems.
This new process realizes the so-called bionic design, which simulates natural structures such as human bones, and only adds materials to the loaded area to adapt the structure of the piston to the load. This process saves materials, and compared with pistons manufactured by traditional methods, 3D printed pistons are 20% lighter and more robust.
In addition, MAHLE's developers inserted a properly placed and specially shaped cooling corridor near the piston ring. The design is based on MAHLE’s years of experience in piston thermal processes and can only be made using 3D printing. The cooling gallery reduces the temperature load on the piston crown (a particularly pressurized part of the piston), thereby optimizing engine combustion and paving the way for the engine to achieve higher top speeds.
This new production process is based on a special aluminum alloy developed by MAHLE, which has been successfully used in casting pistons for a long time. First, the alloy is atomized into a fine powder, and then printed using the laser metal melting (LMF) process. The laser beam melts the powder to the required thickness, and then adds a layer on top of it, adding one layer at a time until the piston is manufactured. Using this method, 3D printing expert Trumpf was able to produce a piston blank made of 1,200 layers of powder in about 12 hours.
Then, MAHLE finally processed, measured and tested the piston blank to ensure that it must meet the strict standards used in traditional manufacturing components. Special attention should be paid to the central area of the piston-the piston skirt, and the part connected with the connecting rod-the pin hole. To perform skirt impulse and tear tests on such areas, MAHLE engineers can simulate the load that the piston may be subjected to during future operations.
In addition to cutting the piston for analysis, the project partner Carl Zeiss (Zeiss) also used CT scans, 3D scans and microscopes to conduct a large number of non-destructive tests. The results show that the printed pistons meet the same high quality standards as conventionally produced pistons. In the actual test, the Porsche 911 GT2 RS engine was equipped with 6 pistons, and the drive unit successfully completed a 200-hour endurance test under the most difficult conditions on the test bench. This includes driving about 6000 kilometers (including refueling) at an average speed of 250 km/h, and running for about 135 hours under full load conditions; it also includes 25 hours of load operation, that is, the vehicle runs in extreme mode.
Another part of the joint Porsche and Trumpf project also demonstrated the advantages of 3D printing, namely an additional charge air cooling machine, which is hidden in the air duct between the turbine and the original charge air cooler, due to the use of 3D printing. As a result, the additional component has a larger heat transfer surface, which can optimize the control of air flow and air cooling, making the incoming air cooler, improving engine performance and reducing fuel consumption.
MAHLE plans to further utilize the potential of new manufacturing processes such as 3D printing in future projects to expand its competitiveness in this field. The shorter development and production time is a huge advantage, especially for new technologies such as electric mobility. In the field of electric mobility, in electric vehicles, motors or gearbox housings and battery systems, thermal management components with complex structures are required to cool and regulate air. The optimization of motor peripheral components such as air passages, filter housings and oil management components also need to rely on such new processes.
This process has also found demand in the aftermarket where small batches of research and development and production of discontinued parts are supplied to historical vehicles. Other promising application areas include rapid prototyping, such as rapid construction of parts for testing, and reverse manufacturing, which uses 3D scanning to replicate parts.