Durable 3D-printed pistons for Porsche

MAHLE, in collaboration with Porsche and machine manufacturer Trumpf, is showing the world what today’s 3D printing technology is capable of. High-performance pistons that are produced using the laser metal fusion (LMF) process can make a 700 hp engine even more powerful.

Joint pioneering work

A bionic-design piston produced by MAHLE using 3D printing for the Porsche 911 GT2 RS
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For some time now, the subject of 3D printing has been unavoidable for anyone wanting to keep up to date with the latest technical developments. This is a technology that is also set to play a key role in the automotive industry. In fact, it has already arrived. MAHLE, along with Porsche and machine manufacturer Trumpf, has started leading the way. Together, the three companies have produced the world’s first high-performance aluminum pistons with 3D printing. The pistons were tested in the Porsche 911 GT2 RS.

More power and greater efficiency

3D printing makes it possible to produce piston designs that would have been unthinkable with casting or forging technology. Bionic optimization of the piston structure means that material can be confined to stressed areas, cutting material use, and making for a lighter piston compared to conventional versions. A cooling gallery has also been integrated, which would not have been possible in previous designs. This reduces the temperature significantly in areas of the piston that are subject to particularly high loads.

The resulting benefits for the engine performance of the Porsche 911 GT2 RS are considerably increased engine speeds and optimized combustion. This squeezes up to 30 hp more out of the already powerful 700 hp engine.

3D printing - here’s how it works

In 3D printing, also known as additive manufacturing, material is usually applied in layers and melted with a laser to create three-dimensional objects. The engine pistons described here were printed using the LMF process, in which a laser beam is applied to fuse metallic powder one layer at a time to create a solid metal component. MAHLE’s engineers have developed a printable powder for this process based on a proven aluminum alloy used in piston casting. This powder is subject to a number of requirements regarding purity and composition. The printing results were finally examined in detail by the measurement technology specialists at Zeiss, using equipment such as scanning electron microscopes and X-ray CT scanners.

Less weight—more possibilities

The additionally integrated cooling channel lowers the temperature in the particularly stressed areas of the piston
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3D printing opens up the possibility of bionic design. In this approach, material can be confined to areas where it is truly needed, thereby saving weight and increasing efficiency in comparison with cast objects. The result: the new piston is ten percent lighter than the forged version currently in use in the 911 GT2 RS. Simulations show that weight savings of up to 20 percent are theoretically possible.

MAHLE’s engineers, however, also benefited from 3D printing in another way: it reduced the number of production-related constraints during the design process. For example, the 3D-printed piston incorporates an annular cooling gallery at a location that would be out of the question in a conventionally manufactured piston. This reduces the temperature by more than 20 kelvin at the relevant point in the engine.

Great advantages—great challenges

A layered approach: A laser fuses around 1,200 layers of the powdered MAHLE piston alloy to form a blank. ©Trumpf
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3D printing offers one major advantage: there is no need to prepare molds to cast the pistons. This allows for the rapid printing and testing of several design variants, thus creating prototypes much faster and cheaper.

Should we expect MAHLE to switch to 3D printing for all its pistons in the near future? No. The costs for a printed piston are still significantly higher than those for its conventionally manufactured counterpart. Currently, additive manufacturing is mainly a viable option for the creation of prototypes and for small-lot production. Casting and forging processes remain the first choice for larger series production.

Watch our video for more details about the 3D-printed piston:

 

Achieving our goals together

This technological leap was made possible due to the close collaboration between three strong players: sports car manufacturer Porsche, MAHLE as development partner for pistons, and 3D printing pioneer Trumpf. Although this lighthouse project initially focuses on sports cars, its ultimate message is that the possibilities of the combustion engine have not yet been exhausted. Leaps in efficiency are still possible with 3D printing. This benefits not only engine performance, but also the environment.

Frank Ickinger, project manager at Porsche, explains: “Thanks to the close cooperation of everyone involved, we were able to further improve upon an absolutely premium product, the Porsche 911 GT2 RS. Technologically speaking, this is the start of a new chapter for us, which opens up completely new possibilities in design and production.”

A future technology

MAHLE is set to harness the potential of new production processes, such as 3D printing, for further projects and aims to systematically expand its competence in this area. Shorter development and production times present a great advantage. This is particularly true when it comes to new technologies such as e mobility, where complex components are needed for cooling and air conditioning, motor or transmission housings, and battery systems in electric vehicles. Further examples include optimized parts in the engine periphery, such as air pathways, filter housings, and oil management components. Demand has also been identified in the development of small lots and the supply of discontinued components to the aftermarket for historic vehicles. Other promising fields of application involve rapid prototyping (the quick construction of parts for testing) and reverse engineering (the reproduction of components from a 3D scan). On the other hand, additive manufacturing is already being employed in numerous MAHLE production plants, allowing spare parts for production machines or fixtures to be procured quickly and economically.

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