Breakthrough in Welding Increases GM Fuel Economy
Thousands of man-hours go into the design of a vehicle, including frame, drive-train, body, and suspension, all to come up with a final product that combines form and function without wasting materials and money. Among the first things to consider when attempting to increase fuel economy in a vehicle is weight reduction, and it’s also among the most difficult.
Every piece of the vehicle, bolted, welded, or glued into place, serves some function structurally, whether to hold everything together, or to keep the occupants safe in an accident. To that end, structural engineers use various materials to achieve the proper balance between weight and strength. For decades, manufacturers have been spot-welding steel pieces to build strong vehicle bodies. In order to reduce weight, manufacturers had to look to other components. Changing from cast-iron cylinder-blocks to cast aluminum is one such example.
Spot-welding involves the use of two electrodes on either side of two or more pieces to be attached, and under compression and 5-15,000 Amps of electricity, the pieces melt together permanently. Auto manufacturers use this method to construct complex body structures out of many individual steel pieces, quickly and efficiently, using robot welders. Aluminum has excellent structural properties, but lightweight and strong aluminum body structures have been out of reach of structural engineers mainly because reliable aluminum spot-welding has been difficult to achieve in a production environment.
General Motors has patented a new, multi-ring domed electrode that has made possible the reliable welding of aluminum pieces, which the previous smooth electrodes, used for steel, were unable to achieve. “The ability to weld aluminum body structures and closures in such a robust fashion will give GM a unique manufacturing advantage,” said Jon Lauckner, GM chief technology officer and vice president of Global R&D. The new electrodes will enable the manufacture of more complex aluminum structures, that before would have required rivets or bolts and much more complex manufacturing techniques.
Regarding weight reduction, AluminumTransportation.org calculates over 5% fuel savings for every 10% in weight reduction, and changing from steel to aluminum results in better performance, economy, and safety. The patented process has already gone into the production of the engine hood of the 2012 Cadillac CTS-V and the liftgate of the Hybrid Chevrolet Tahoe and GMC Yukon, eliminating almost two pounds of rivets. GM plans to expand the use of the new technology starting in 2013 and is hoping that this patented process will give them an edge in fuel economy by making an early switch to aluminum.