The automotive world has seen growing interest in 3D printing, with manufacturers using the technology both for prototyping and end-use parts. The latest manufacturer to take a leap with 3D printing is Bugatti, maker of the Veyron and Chiron super cars. Its new eight-piston monobloc brake caliper has a long list of distinctions – it’s the first 3D printed brake caliper, for one thing, as well as being the largest brake caliper in the automotive industry. It’s also the largest titanium component to be produced by 3D printing.
The caliper was developed in cooperation with Laser Zentrum Nord, part of the Fraunhofer research organization. Vehicle trials for the use of the part in series production are expected to start in the first half of this year.
“Vehicle development is a never-ending process. This is particularly true at Bugatti,” said Frank Götzke, Head of New Technologies in the Technical Development Department of Bugatti Automobiles S.A.S. “In our continuing development efforts, we are always considering how new materials and processes can be used to make our current model even better and how future vehicles of our brand 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.”
In another record-setting title, Bugatti currently uses the most powerful brakes in the world on the new Chiron. Its brake calipers are forged from high-strength aluminum alloy. Featuring eight titanium pistons on each of the front calipers and six on the rear ones, they’re the largest calipers currently installed on a production vehicle. The inspiration for their design comes from motorsports and combines minimum weight with maximum stiffness.
The new titanium brake caliper, however, goes a step further. It was 3D printed from a titanium alloy commonly used in the aerospace industry, in aircraft or rocket engines or for highly stressed undercarriage and wing components. It offers much better performance than aluminum, possessing a tensile strength of 1,250 N/mm2. This means that a square millimeter of the material can withstand force of a little more than 125 kg without rupturing. It’s also very lightweight: the caliper, which is 41 cm long, 21 cm high and 13.6 cm high, weighs only 2.9 kg. The aluminum component, in comparison, weighs 4.9 kg, meaning that 3D printing it in titanium reduced the weight by about 40% while increasing strength.
Using titanium as a material to make calipers wasn’t realistic in the past, because it’s extremely difficult to mill or forge components from a titanium block due to its high strength. 3D printing it, however, is a different story. Not only does the technology allow for the components to be created from titanium, it allows them to be stiffer, stronger, and more complex in geometry.
Bugatti 3D printed the caliper using a high-performance SLM machine at Laser Zentrum Nord. At the beginning of the project, it was the largest titanium 3D printer in the world.
“Laser Zentrum Nord is one of many scientific institutes with which we have developed very good cooperation over the years,” Götzke said. “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.”
The scientists at Laser Zentrum Nord have won several prestigious national and international innovation awards over the past few years.
Prof. Dr.-Ing. Claus Emmelmann was formerly Managing Director of Laser Zentrum Nord GmbH and has been Head of the Fraunhofer Institute for Additive Production Technologies (Fraunhofer IAPT) since Laser Zentrum Nord was incorporated in the Fraunhofer research organization under this name at the beginning of the year. He also heads the Institute of Laser and System Technologies (iLAS) of Hamburg University of Technology.
“Cooperation with Bugatti is a key lighthouse project for us,” he said. “We were thrilled to be contacted by Bugatti. I do not know any other carmaker which makes such extreme demands of its products. We were pleased to face up to this challenge.”
The caliper required a short development time of only about three months. Bugatti sent the basic concept as well as the strength and stiffness simulations and calculations and design drawings to Laser Zentrum Nord as a complete data package. Laser Zentrum Nord then carried out process simulation, design of support structures, and 3D printing. Bugatti handled the finishing of the component.
The 3D printer is equipped with four lasers, and took 45 hours to print the brake caliper. The total number of printed layers required to complete the part is 2,213. After the 3D printing process was complete, the part was heat treated in a furnace reaching temperatures as high as 700°C to eliminate residual stress and ensure dimensional stability. The supports were then removed, and the part’s surface was smoothed in a mechanical, chemical and process that greatly improves its fatigue strength. The contours of the functional surfaces were then CNC machined in a process that took another 11 hours.
Finally, Bugatti had a finely shaped caliper with wall thicknesses between one and four millimeters.
“It was a very moving moment for the team when we held our first titanium brake caliper from the 3-D printer in our hands,” Götzke said. “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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