Laser welding leads to Corvette's strength, refinement and quality

Bowling Green, KY - General Motors' $131 million investment in technology at the Bowling Green Assembly Plant, which includes the first production use of a GM-patented process, allowing aluminum to be spot welded to aluminum and laser welding of aluminum panels, is resulting in the strongest and most precisely built Corvette in its six-decade history.

To show off the Corvette and its plant, public tours at the plant will resume on Monday, October 14. The plant tour and customer programs were halted last fall while the plant underwent the upgrade. The sports car has been built there exclusively since June 1981.

New technologies enable more accurate and efficiently produced subassemblies such as the frame and the components attached to it. "For example, the new aluminum-welding process enabled us to make the frame lighter and stiffer, improving the performance and driving confidence," said Dave Tatman, plant manager.

Approximately $52 million of the investment went to a new body shop that manufactures the car's all-new, lightweight aluminum frame in-house for the first time. The frame is not only the foundation for the car's greater driving capabilities, but the platform on which the 2014 Corvette Stingray (see photo above) is more precisely constructed. It is 99 pounds (45 kg) lighter and is 57 percent stiffer than the previous-generation frame, resulting in a chassis so strong that the convertible model needs no structural reinforcements.

It is also the most complex frame design in the Corvette's history, featuring main rails composed of five customized aluminum segments, including aluminum extrusions at each end, a center main rail section and hollow-cast nodes at the suspension interface points, all with varied thicknesses that make the most of the strength and mass requirements of each respective section.

Assembling the frame requires more advanced joining processes and more precise inspection methods to ensure strength and dimensional accuracy. That is where aluminum welding, Flowdrill-type fastening and laser welding help ensure the high-quality targets for the frame.

Flowdrill fastening
The Corvette Stingray's frame features 188 Flowdrill-machined fasteners with structural adhesive. The fasteners are installed by a high-speed drill that extrudes the frame material to create a strong, integral collar that is tapped for screw-type fasteners. It is a GM first for body structure joining.

Aluminum resistance spot welding
Pioneered by GM, the aluminum resistance spot-welding process is an efficient method for joining aluminum to aluminum where there is two-sided joint access. It is particularly effective with the thicker materials, up to 4mm, used on the new Corvette's frame. It is also used for welding aluminum extrusions, die castings, and aluminum sheet metal. There are 439 aluminum resistance spot welds on the Corvette Stingray coupe.

Laser welding
Laser welding is used in the frame's tunnel subassembly to attach sheet aluminum closeout panels to the tunnel structure. The process enables continuous welding quickly when only single-sided access is available.

Additionally, the precise beam of high energy used in the welding process minimizes heat beyond the weld area for improved structural accuracy, and the laser process creates a leak-free joint that does not require additional sealing, which could add weight to the frame structure.

There are two robotic laser welding stations in the plant, one with a pair of robots and another with a single robot. Each robot has a dedicated laser power generator, and together, they lay down 71 segments for a total of 37 welded feet on every frame.

Shipping of the Corvette Stingray Coupe to dealers started Sept. 18. Pricing for the 2014 Corvette Stingray Coupe starts at $51,995, including destination, and the Convertible is priced at $56,995 including destination.

Tour guidelines and reservations are available at www.corvetteassembly.com.

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Photo copyright General Motors