Bugatti 3D prints eight-piston monobloc brake caliper

This brake caliper is the largest titanium functional component produced by 3-D printing in the world – developed by Bugatti. The photo shows the caliper together with pistons and pads. © 2018 Bugatti Automobiles S.A.S.

French super sport car maker, Bugatti, has a history of pushing the limits of vehicle design and technical innovation.

Bugatti engineers are using 3D printing to manufacture the latest brake caliper design, which has allowed them to play around with materials and design features. For the most part, aluminum has been used for vehicle components, but the Bugatti brake caliper is made using titanium. The company boasts that this is one of the world’s largest functional component produced from titanium using 3D printing processes.

The automaker worked with Laser Zentrum Nord of Hamburg, an institute that has formed part of the Fraunhofer research organization. Vehicle trials for the use of the 3D titanium brake caliper in series production are to start in the first half of the year.

“Vehicle development is a never-ending process. This is particularly true at Bugatti,” says 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,” adds the 48-year-old machine tool and production technician, who holds a degree in engineering. The company is always exploring how new materials and processes can be used to make their current models better and open the doors to new designs.

According to the company, Bugatti’s Chiron currently uses the most powerful brakes in the world. The brake calipers were an entirely new development. They are forged from a block of high-strength aluminium alloy. With eight titanium pistons on each of the front calipers and six on each of the rear units, these are also the largest brake calipers currently installed on a production vehicle. The brake calipers of the Chiron are produced using bionic principles on the basis of a natural model. The new architecture combines minimum weight with maximum stiffness.

The 3D printed brake caliper uses a particular titanium alloy, with the scientific designation of Ti6AI4V, which is mainly used in the aerospace industry. The material offers considerably higher performance than aluminium—it has a tensile strength of 1,250 N/mm2. This means that a force of slightly more than 125 kg be applied to a square millimetre of this titanium alloy without the material rupturing. The new titanium brake caliper, which is 41 cm long, 21 cm wide and 13.6 cm high, weighs only 2.9 kg. In comparison with the aluminium component currently used, which weighs 4.9 kg.

Due to the extremely high strength of titanium, it was challenging to use with traditional milling or forging methods. So Frank Götzke looked into 3D printing and found the selective laser melting units required in Hamburg, at Laser Zentrum Nord.

The 3D printed titanium brake caliper only took about three months to develop. 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, the design of the supporting structures, actual printing and the treatment of the component. Bugatti was responsible for finishing.

The 3D printer at Laser Zentrum Nord is equipped with four 400-watt lasers with itanium powder deposited layer by layer. With each layer, the four lasers melt the titanium powder into the shape defined for the brake caliper. The material cools immediately and the brake caliper take shape. The total number of layers required is 2,213 and it took approximately 45 hours.

Following the completion of the final layer, the remaining titanium powder which had not melted is removed from the chamber, cleaned and preserved for reuse in a closed loop. What remains in the chamber is a brake caliper complete with supporting structure which maintains its shape until it has received stabilizing heat treatment and reached its final strength.

Heat treatment is carried out in a furnace where the brake caliper is exposed to an initial temperature of 700°C, falling to 100°C in the course of the process, in order to eliminate residual stress and to ensure dimensional stability. Finally, the supporting structures are removed and the component is separated from the tray. In the next production stage, the surface is smoothed in a combined mechanical, physical and chemical process which drastically improves its fatigue strength. 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 its work.

The brake caliper is a delicately shaped component with wall thicknesses between a minimum of only one millimetre and a maximum of four millimetres.

www.bugatti.com