Cleveland, Ohio – Conventional wisdom holds that 3D printing and other additive technologies are too slow for practical use in automotive manufacturing. But not all automakers produce hundreds of thousands of each model each year.
Case in point, Volkswagen’s Bugatti luxury supercar brand.
Making only a handful of Chiron cars per year, vehicles that cost about $2.6 million and go from 0mph to 249mph in 32.6 seconds, Bugatti takes the mass out of mass production, making it a better candidate than the primary VW brand to try out printed parts.
Bugatti engineers are testing titanium brake calipers, the largest functional titanium pieces to ever be produced on 3D printers, for use in future vehicles.
VW engineers worked with manufacturing and materials experts from Zentrum Nord of Hamburg, Gernany, part of the Fraunhofer research organization.
“Vehicle development is a never-ending process,” says Frank Götzke, head of New Technologies in the Technical Development Department of Bugatti Automobiles S.A.S. “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.”
The current brakes on the Chiron, forged from a block of high-strength aluminum alloy, have eight titanium pistons on each of the front calipers and six on each of the rear units.
Moving to the aerospace titanium alloy Ti6AI4V increases performance compared to aluminum parts. With a tensile strength of 1,250 N/mm2, the titanium parts better resists rupturing than the aluminum components, and it is lighter. The 41cm x 21cm x 13.6cm part weighs 2.9kg, 41% less than the aluminum component.
Development time for the 3D-printed titanium brake caliper was shorter than usual – going from concept to testing in about three months.
It takes a total of 45 hours to print a brake caliper. During this time, titanium powder is deposited layer by layer. With each layer, four 400W lasers melt the powder into shape – repeating the process 2,213 times to finish each caliper.
Following printing, heat treatment exposes calipers to 700°C, before lowering the temperature to 100°C. The falling temperatures eliminate residual stress and to ensure dimensional stability.
Supporting structures are then removed, and the component is separated from the tray. The surface is smoothed using mechanical, physical, and chemical processes. Finally, 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.
The result: a delicately shaped component with wall thicknesses between 1mm and 4mm.
The first trials for use in production vehicles are due to be held in the first half of the year; the time schedule is still to be finalized.