Technologies Of The Year -- Making A Material Difference

Dec. 21, 2004
Aluminum Vehicle Technology (AVT) from Alcan Inc. helped Jaguar introduce its 2004 XJ, an industry-first use of rivet-bonding, monocoque (unit body) construction.

Prediction: within 25 years, the production of aluminum automobiles will exceed those made of steel. That's the operating presumption that has led Jaguar Motor Cars Ltd. to go beyond dabbling in aluminum via prototypes or limited volume models. "With the 2004 XJ designed for aluminum, Jaguar's flagship moves to where the future is going to be," says David Scholes, chief program engineer. The drivers: the need to maintain the brand's traditional levels of luxury and performance while satisfying society's growing quest for energy efficiency, he adds. Making the future work depends on tailoring a manufacturing strategy for volume production with the new material. For example, the XJ models sold since their 1968 introduction, about 800,000, represent about half the total number of Jaguars ever produced. To meet the objectives for the XJ program, Jaguar elected to incorporate the Aluminum Vehicle Technology (AVT) system of its material supplier, Alcan Inc. The result provides a winning example of how to gain the weight-saving potential of aluminum technology with manufacturing methods similar to those now in use for conventional steel unit body construction. Rather than requiring radically new manufacturing procedures, Alcan's AVT system gives Jaguar the ability to operate within existing automotive manufacturing processes with modifications mainly in tooling and handling, adds Scholes. Compared with the 2003 XJ, he says the new aluminum model is 60% stiffer and 40% lighter despite being 4.3 inches taller and 2.6 inches longer. The aluminum body of the new XJ weighs just 485 pounds -- the steel equivalent is 794 pounds. Jaguar says the XJ is up to 570 pounds lighter than the competition. He notes that competitor Audi, which also has switched to aluminum for its top-of-the line A8 sedan, uses a space-frame construction concept that substantially alters the vehicle assembly process and equipment. Alcan says its AVT technology is less labor intensive and does not have some of the joining complexity issues associated with space-frame construction. "One of the success values of the XJ program is that it demonstrates that [switching to aluminum] can be done," says Alcan Automotive's Cleveland-based Mike Kelly, vice president, external and customer relationships. "And it can be done via a conventional automotive stamping, assembly and painting systems." The AVT system begins with heat-treated aluminum sheet that Alcan tailors to Jaguar's manufacturing process. Alcan's sheet preparation includes surface treatment to enhance adhesive bonding and lubricants to facilitate stamping. At Jaguar's UK plant at Castle Bromwich, sheet assembly involves robots that apply self-piercing rivets and aerospace-grade one-part epoxy adhesives. The adhesive heat-cures to optimal strength during the vehicle painting process. Almost 3,200 rivets and 394 feet of adhesive bead are applied. The completed vehicle, powered by a 4.2-liter dual-cam V-8, weighs 3,766 pounds with an EPA city/highway rating of 18/28. The supercharged engine provides 390 horsepower, enough to launch the vehicle from standstill to 60 mph in just 5.0 seconds. The bottom line: AVT technology can make a material contribution to performance and luxury without overwhelming the manufacturing process or requiring the payment of gas-guzzler taxes.

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