The prototype pistons are lighter than a cast part, but thanks to their 3D printing optimization and "bionic" structure they are just as strong.

Porsche

Porsche has its first endurance test with 3D-printed pistons in the engine of the 911 GT2 RS. The part not only survived, but the car manufacturer's investigations showed that the pistons made of printed aluminum alloy correspond to (and even surpass) comparable cast or forged parts.

Porsche has been in 3D printing for a while. The automaker has been using 3D printing for rapid prototyping and part development since the 1990s and currently sells about 20 printed plastics, steel and alloy prints "Porsche Classic" Production parts for heritage cars. Orders for 911 and 718 motorsport variants with full bucket seats have recently been opened so customers can specify the strength, color and shape of the engine 3D printed cushion and backrest surfaces. However, these pistons could be the most ambitious automotive application of 3D printing technology to date.

The process begins with redesigning the piston, taking into account the benefits of 3D printing. Porsche used computer simulation and artificial intelligence to optimize the shape and underlying topology of the piston, remove material where it wasn't needed, and add it where it was needed. The result is what the automaker calls a "bionic" design that uses an organic structural shape. Part of 3D printing optimization involves minimizing the substrate that has to be processed later. I was told that the only support that needs to be removed is the hole for the wrist pin.

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Like their cast and forged counterparts, the printed pistons are still heat treated and machined to increase strength and precision.

Porsche

Porsche was also able to integrate a cooling channel in the piston structure and separately design special double-jet oil nozzles. These additive manufacturing services would be impossible – or at least extremely difficult – to achieve with machining or casting, the automaker claims. Since the design was sorted and tested many times in simulation, it was time to actually print the part that required much more specialized hardware than the hobby printer made of plastic filaments in your shed.

The pistons are manufactured in a high-precision Trumpf TruPrint 3000 laser 3D printer, in which the parts basically each form a layer of 0.02 to 0.1 millimeters by welding a fine metal powder with powerful, precise lasers. The material used is a proprietary aluminum alloy called M174 +, which is developed and provided by the partner and parts manufacturer Mahle. Each piston consists of approximately 1,200 layers of the molten alloy, the pressure of which takes approximately 12 hours. Fortunately, you can print them in batches.

Porsche and its partners claim that the properties of the end product are comparable to those of cast material for production pistons. To ensure that the automaker is also working closely with Zeiss, a German manufacturer of optical systems, to test and measure the material with a light microscope, inspection, electron microscope scanning, X-ray microscope and 3D scanning. Examples of the printed pistons were also torn off and analyzed.

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The prototype pistons were installed in a Porsche 911 GT2 RS engine and subjected to exhaustive endurance tests for 200 hours.

Porsche

Six pistons were then hammered into a 3.8-liter six-cylinder engine with two turbochargers and 911 GT2 RS in a laboratory to begin a practical endurance test. The evaluation included 24 hours of simulated high-speed driving, simulating the rigors of the race track over 6,000 km at an average speed of 250 km / h. Porsche even went as far as simulating stops to refuel. Next, the engineers ran the pistons at different speeds for 135 hours at full load and 25 hours under towing load. Two hundred hours later, the test was considered a success because all six pistons had passed.

Each 3D-printed aluminum piston is 10 percent lighter than the forged piston that the GT2 RS normally uses, and runs more than 20 degrees cooler thanks to the new channel in the piston ring area. That means the engine can turn higher and unlock additional power. According to Frank Ickinger of the Advance Drive Development department at Porsche, "an additional 300 rpm corresponds to about 30 (HP) more."

And that's when Porsche plays it safe. The automaker is already thinking about the butterfly effect that these lighter, cooler 3D-printed pistons can have on the engine design.

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The partners Mahle, Trumpf and Zeiss ensured that the strength, density and precision of the parts were up to date throughout the development.

Porsche

"We have always made sure that we are on the safe side," says Ickinger. "Our simulations show that a potential weight saving of up to 20 percent can be achieved per piston."

"The torsional vibration damper can then be made smaller," he continues, "which makes the engine turn even more freely. Increased thermal resistance due to the lower temperature enables higher combustion pressures and an even more advanced ignition point – both factors that increase." Performance and efficiency. "

The 3D-printed GT2 RS pistons are still in the early development phase, without specific production plans being specified. However, Porsche is aware that the technology will stay here and has a roadmap for more 3D-printed parts that will end up in special production cars and eventually series production vehicles. By researching copper as a 3D printing material, the technology even has the potential to find interesting new applications in the manufacture of electric cars.

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These pistons are the most ambitious application of additive manufacturing for auto parts that I have seen.

Porsche

"I am sure that additive manufacturing will be an integral part of automotive development and production in 10 years at the latest," says Ickinger.

Porsche is not the only car manufacturer to develop additive manufacturing parts. BMW has invested in 3D metal printing and experimented with 3D printed customization parts for the Mini Yours program. In the meantime, the French hyperauto maker Bugatti has demonstrated (and spectacularly tested for torture). 3D printed titanium brake calipers.

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