June 2009 eNews

5-axis machining helps aluminum wheels spin into history

When Automobili Lamborghini decided it wanted lightweight wheels for its $350,000+ super sports car, the Murciélago LP 670-4 SuperVeloce, it turned to Alcoa Auto Wheels — and the engineering behind the forged aluminum wheels enabled a 20 percent weight savings over a comparable cast aluminum wheel.

The forged aluminum wheels reduce un-sprung weight and contribute to the SV’s 100kg (220lb) mass reduction over the standard Murciélago.

The “Ares” five twin-spoke design results in a metal structure that improves strength and durability, offering the opportunity to create strong and lightweight wheels, said David Yates, of Alcoa Auto Wheels-Europe. The 18"x8.5" front wheel weighs 19.6lbs and the 18"x13" rear wheel weighs 27.2lbs.

The forged aluminum wheels contribute to the all-wheel drive SV’s 100kg (220lbs) mass reduction over the standard Murciélago.

Aluminum wheels for Automobili Lamborghini are forged at Alcoa’s Cleveland,OH, works plant. The forging process starts with extrusions of aerospace-grade 6061-T6 aluminum considered the premium alloy for top strength properties optimizing wheel design and production.

The aluminum billet is prepared and then subjected to large forging presses, ranging from 4,000-8,000 tons, and extensive heat treatment and curing processes are performed on-site for the best possible wheel strength.

Alcoa one-piece forging design aligns the metal grain in a uniform direction along the contours of the wheel, increasing strength, resulting in a finished wheel that is strong and lightweight.

“For the most part, we utilize 5-axis machining, allowing creative options to get in to machine in tight spaces within the wheel forging,” explained Brian Thomas, of Alcoa Wheel and Transportation Products. “They provide inside and outside machining capability.” Alcoa outsources the machining.

The challenges are taking weight out of the forged wheel through CAD/CAM design and then getting into the 5-axis machining to be able to take away as much metal as possible while maintaining strength, Thomas added.

“Tight tolerances generate an attractive wheel complete with deep pockets, intricate design, et cetera, but more importantly, they generate a wheel that has a truer rotation and uniformity,” he said. ”Machining and finishing quality allows a quality finish (painted in the case of SuperVeloce).”

Lamborghini calls its Murciélago LP 670-4 one of the most extraordinary super sports cars of all time. The SuperVeloce is more powerful, lighter, and faster than the Murciélago LP 640, with the output of the 6.5L V12 increased to 670hp, a Lamborghini spokesman said.

The vehicle has a power-to-weight ratio of 2.3kg (5.1lbs) per hp, allowing it to speed from 0 to 100 km/h (62mph) in 3.2 seconds with a top speed of around 342m/h (212mph).

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Alcoa Auto Wheels

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