With its Veyron and Chiron super sports cars, Bugatti Automobiles has established itself as a pioneer in the extreme performance sector of the automotive industry. Now it has achieved a new coup, designing a brake caliper that can be produced by 3D printing.

Moreover, while the main material used for the additive production of vehicle components to date has been aluminium, the new brake caliper is made from titanium. This is therefore the world’s largest functional component 3D printed from titanium. Vehicle trials for the use of the 3D titanium brake caliper in series production are to start by mid-2018.

“Vehicle development is a never-ending process. This is particularly true at Bugatti,” says Frank Götzke, Head of New Technologies in Bugatti’s Technical Development Department. “We are always considering how new materials and processes can be used to make our current model even better and how future vehicles could be designed. As our performance data are often at the physical limits, we are especially demanding. This is why Bugatti always goes at least one step further than other manufacturers in the development of technical solutions.”

Götzke joined Bugatti in 2001 and played a key role in the development of both the Veyron and the Chiron. Bugatti currently uses the most powerful brakes in the world on the new Chiron, with calipers forged from high-strength aluminium alloy. Featuring eight titanium pistons on each front caliper and six on each rear unit, they are also the largest brake calipers currently installed on a production vehicle, combining minimum weight with maximum stiffness.

With the new, 3D-printed titanium brake caliper, Bugatti is now going one step further. This particular titanium alloy, Ti6AI4V, is mainly used in aerospace, for example in highly stressed undercarriage and wing components or in aircraft and rocket engines. The material offers considerably higher performance than aluminium – even as a 3D-printed component, it has a tensile strength of 1,250N per square millimetre.

The new titanium brake caliper, which is 41cm long, 21cm wide and 13.6cm high, weighs only 2.9kg. The aluminium component currently used weighs 4.9kg, so Bugatti could reduce the weight of the caliper by about 40% while ensuring even higher strength by using the new part.

This approach was previously not feasible because it is extremely difficult to mill or forge components from titanium due to its extremely high strength. This problem has been solved using an extremely high-performance 3D printer, which also opens up the possibility of generating even more complex structures that are significantly stiffer and stronger than with conventional production process.

Götzke found the selective laser melting units required at Laser Zentrum Nord in Hamburg. Over the past few years, Laser Zentrum Nord has received a large number of national and international innovation awards for its work in industry.

“Laser Zentrum Nord is one of many scientific institutes with which we have developed very good cooperation over the years,” Götzke explains. “Thanks to the large number of projects completed, mainly for the aviation industry, the institute has comprehensive know-how especially in the field of titanium processing and offers mature technology.”

Development for the 3D-printed brake caliper was very quick, about three months from the first idea to the first printed component. The basic concept, the strength and stiffness simulations and calculations and the design drawings were sent to Laser Zentrum Nord by Bugatti as a complete data package. The institute then carried out process simulation, design of supporting structures, actual printing and the treatment of the component. Bugatti was responsible for finishing.

The special 3D printer at Laser Zentrum Nord is equipped with four 400W lasers. Titanium powder is deposited layer by layer, with the lasers melting it into the shape defined for the brake caliper. The material cools immediately and the caliper take shape. It takes 45 hours to print the brake caliper, with a total of 2,213 layers required.

Following completion of the final layer, any remaining titanium powder that has not melted is removed. What remains is a brake caliper, with a supporting structure to maintain its shape until it receives stabilising heat treatment. This is carried out in a furnace where the caliper is exposed to an initial temperature of 700 degrees Celsius, falling to 100 degrees during the process, to eliminate residual stress and ensure dimensional stability. Finally, the supporting structures are removed and the component is separated from the tray.

In the next stage, the surface is smoothed in a combined mechanical, physical and chemical process that drastically improves fatigue strength – the component’s long-term durability. Finally, the contours of functional surfaces, such as the piston contact surfaces or threads, are machined in a five-axis milling machine, which takes another 11 hours to complete.

The result is a delicately shaped component with wall thicknesses between one and four millimetres.

“It was a very moving moment for the team when we held our first titanium brake caliper from the 3D printer in our hands,” Götzke recalls. “In terms of volume, this is the largest functional component produced from titanium by additive manufacturing methods. Everyone who looks at the part is surprised at how light it is – despite its large size. Technically, this is an extremely impressive brake caliper, and it also looks great.”

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