BMW makes water pump wheel using 3D printer

BMW will see the current season of the German Touring Car Masters (DTM) open with a small anniversary. One of the powertrains is fitted with the 500th water pump wheel made on a 3D printer.

The high-precision component, which is subject to high stresses, consists of an aluminium alloy and has previously proven its worth in the tough environment of motorsports.

In a race, the high-performance powertrains run up to 70 percent of the time under full load; in addition, the moving parts in particular have to handle extreme conditions. Back in 2010, the BMW engineering team developed a one-piece, light-metal water pump wheel to replace the previously applied series plastic part.

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Based on BMW’s long-standing experience in additive production methods, which are becoming better known under the collective term of ‘3D printing’, the engineers decided from the outset to apply the SLM (selective laser melting) procedure in the production of the small series.

In this laser-fusing procedure, the component is created in a generative layering process: The 3D printer applies 0.05-millimetre- thin layers of the metal powder coat to a processing plate. A laser beam then fuses the powder at the desired spots under an inert atmosphere to form a durable aluminum layer. This is how, layer by layer, the three-dimensional component takes shape. Compared to 3D print methods in the consumer industries, which use plastic filaments, the additive production of metal parts requires considerably greater expertise in process engineering.

3D printing as a production method has turned out to be the ideal procedure for the small batch. Firstly, it allows for the inclusion of design refinements in the six-bladed centrifugal pump wheel, whose implementation would require much greater effort with other production methods. With the new method, it was possible to achieve ideal aerodynamics of the component for the DTM race series. Secondly, no complex tools or molds are needed, which makes the demand-oriented production more cost-effective. On top of that, 3D printing ensures the dimensional accuracy of the water pump wheel over the entire production time.

BMW says it applies the homologated high-precision part both in the DTM racecars and in the Z4 GT3 customer vehicles.