Ultrasonic welding is widely used by automotive suppliers to weld plastics but, so far, has only limited applications to combine metals. Ford believes Aston Martin is the first to use metal ultrasonic welding for automotive body assembly.
Aston Martin engineers use ultrasonic welding to create the aluminum alloy C-pillar on both the DB9 and the V8 Vantage, which is due next year. This component plays a vital part in helping the body structure meet crash requirements.
"We wanted to use ultrasonic welding on the DB9 due to its lower temperature and therefore lower distortion of critical joints," said Jeremy Main, Aston's director of product development. "It has proved to be an excellent quality enhancement."
Conventional resistance welding used extensively in steel-body assembly has severe limitations for aluminum, including high energy costs, weakening of heated areas and deformed or warped panels.
An ultrasonic weld is 90 percent stronger than a conventional spot weld and it requires 95 percent less energy than conventional resistance welding. Importantly, there is no contamination or change in material characteristics or dimensions of the components.
A key part of the ultrasonic welding process is the Sonotrode ultrasonic probe that oscillates at 20,000 cycles per second (20 kilohertz) to create a molecular-level weld without melting the aluminum panels being welded.
Ultrasonic welding derives from work by Ford's US-based Scientific Research Laboratory in Dearborn, Michigan.
Sonobond Ultrasonics of West Chester, Pennsylvania, USA sold an ultrasonic welding gun to the Ford laboratory. Ford sent two systems to Aston Martin to use in low-volume production to test the technology.
Sonobond ultrasonic welders are already used for wiring harnesses and ignition modules, says Sonobond President Janet Devine.
"Ford has an interest in Sonobond for aluminum ultrasonic welding but I would hope that General Motors, Chrysler and some of the Japanese auto companies would also be interested," Devine says.
Ford and other manufacturers are using a variety of new welding and joining techniques to cope with the manufacturing demands of lightweight materials.
Jaguar, another Ford unit with aluminum-body products, uses Henrob self-piercing rivets on the X350 XJ sedan introduced last year. Self-piercing rivets also will feature in the X150, the XK8 sports car replacement due in 2006.