When Ford Motor Co. moved from steel to aluminum on the F-150 pickup in 2015, the automaker switched from holding the truck’s body together with thousands of spot welds to using rivets, flow-drilled screws, and adhesives. The problem, engineers say, is aluminum riveting is slower and more difficult than steel spot-welding.
“We had to buy fasteners we’d never bought before in very high volumes, and we needed new types of equipment. There was a huge learning curve,” says Shawn M. Morgan, global vehicle architecture manager for Ford Motor Co. “When you switch from spot-welding, it’s difficult. The speeds are slower, so we had to add more line points. The rivet heads are large, so we had to rethink access to the joint. It wasn’t a simple one-for-one trade between rivet robots and weld systems.”
At the 4th Lightweight Vehicle Manufacturing Summit in Detroit, Michigan, automakers and fastener producers discussed the challenges being brought about by the need to cut vehicle weights. Replacing well-understood steel processes with aluminum technology has been taking place, but automaker engineers complain that there’s been some overpromising from suppliers, and joining experts say changing material options and design demands require new product development.
Pete Edwards, joining leader for Honda Engineering North America Inc. in Marysville, Ohio, says he likes the idea of using rivets conceptually, but in practice, there are several barriers to adoption.
“The way Honda is set up, it would be nearly impossible to swap out welding for riveting. We don’t have the space to add more line spots,” Edwards says. Another concern he notes is the lack of flexibility. Honda and many other automakers build several different models on the same assembly lines, something that spot-weld robots can handle with little trouble.
“You can program a welding robot to recognize a lot of different geometries, and the equipment fits. The rivet-driver heads are much larger, and that creates a lot of challenges,” Edwards says. “Our priority is finding the ideal joint for the product and for the most efficient plant-floor layout.”
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From the April 2017 issue of Today’s Motor Vehicles.