Piston from the printer

Porsche is researching pistons for internal combustion engines from the 3D printer. The first stress tests have already been successful.
Pistons from the 3-D printer almost sound like science fiction, but it is a high-tech process that Porsche has great expectations for. And that is already being tested in practice. 3-D printing is nothing new, Porsche is already producing racing seats or spare parts for the classic area in 3-D printing. But now the first pistons created in additive 3-D printing have passed load tests on the engine test bench.

The process has many advantages, explains Frank Ickinger from Porsche pre-development. “What has not been possible until now will be feasible,” enthuses the engineer. “The manufacturing process enables us to optimize the piston structure, integrate a cooling channel and reduce the weight of the piston by ten percent.”

It works like magic

In a 3-D printer from the Swabian company Trumpf, several lasers weld metal powder layer by layer into pistons. Five pistons of a GT2-RS engine (102 mm bore) fit in the printer of the type TruPrint 3000. The metal powder comes from the piston manufacturer Mahle, it consists of a light metal alloy, which is also used for conventionally manufactured cast pistons. Although the process takes around twelve hours – 1200 individual layers melt the lasers together – the process is 30 percent faster overall than conventional processes, in which casting or forging tools first have to be manufactured.

Ickinger knows that additive manufacturing using the so-called laser-metal fusion process also offers engineers design and production technology options that they never dreamed of before.

This makes it possible to use bionic design, to apply material only where there is a flow of force. That saves weight. With a ten percent saving, they stayed on the safe side. “Our simulations show that weight savings of up to 20 percent are possible. Higher speeds thanks to lower oscillating masses are possible. In the case of the GT2 RS, 300 revolutions mean 30 HP more.”

Another special feature of the new pistons is the oil channel integrated behind the piston rings for additional cooling of the thermally particularly stressed area around the piston rings. An annular tunnel runs inside the piston, oil flows through and dissipates heat. “That would not be possible when forging or casting pistons,” says engine engineer Ickinger. Tests showed that this caused the temperature in the area around the exhaust valves to drop by 20 degrees.