The Power of Oneness


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“Design for Assembly” methodology has been around for a few decades now, and the benefits (and profits) of making a designer take a good look at how things are put together on the manufacturing side have long been obvious. “The greatest improvements arose from simplification of the product by reducing the number of separate parts,” say Geoffrey Boothroyd and Peter Dewhurst in their textbook, Product Design for Manufacture and Assembly.

So, if cutting the part count is key, why not cut that count all the way down to one?

That’s just what Sridhar Kota, a professor of mechanical engineering at the University of Michigan and former assistant director for advanced manufacturing for the White House Office, has long been advocating. He calls his method, “Design for No Assembly.”

“When neighboring parts don’t have to be a different material, then you should combine them,” says Kota. “Even if there is rotative motion between parts, you can combine them by exploiting the material’s elasticity.”

Nearly two decades ago, Kota wanted to show how, by taking advantage of a material's natural compliancy, a complex multipiece product could be reduced to a single part. So he attacked a simple but part-heavy device: the windshield wiper. His monolithic prototype was meant to show the engineering world how designers could minimize rigidity, part count, and assembly and still have a superior product.

The experiment was so effective that the auto industry was soon to begin putting them to use clearing off today’s raindrops. “Ours is one piece, performs better than a traditional wiper, costs half as much, and weighs half as much,” says Kota. With nearly 100 million wipers being replaced each year, Kota’s one-count arm and blade is likely to make a massive impact.

The Adaptive Compliant Trailing Edge (ACTE) flap, with a wing surface that can change shape in flight. Image: NASA / Ken Ulbrich

 

While the auto industry was catching up to Kota’s initial proof of concept, Kota was putting the same methodology to use with a much bigger part on a much bigger vehicle. This fall, NASA replaced the flaps on a Gulfstream III with Kota’s “Adaptive Compliant Trailing Edge.” The new system can bend and twist to make the optimal shape for the various stages of flying. In essence, it’s the first morphing wing to really work.

Of course, patents and visionary ideas for morphing wings abound. “But they are all complex, heavy, and with joints,” says Kota. “None of that stuff ever works. If you really want things to flex, why not exploit the elasticity of the material? Then everything becomes lightweight. It’s what made our design possible.”

Instead of turning to stiffness for strength, he looked at how nature handles weight, by distributing strain throughout the entire part. “In my structures, every section of the material shares the load,” Kota says. “That wing supports 2,400 pounds of load. You can put seven pickup trucks on it, and it would move as if there were nothing on it.”

If wipers and wings can be so sharply improved with a little design for no assembly, what about all the other things in the world? In fact, Kota has made scissors, staplers, medical devices and MEMS devices. Shoe companies, furniture companies, automotive companies and sailboat companies have all come to him to help reduce part count. “Think of a name of an aerospace company—they are already working with us,” he says. One company paid him to just walk around and identify things that could be redesigned as a single part.  

To reduce the multiple parts that make up myriad engineered objects in the modern landscape, designers and manufacturers will need more than just one Kota on the job. To that end, he is currently reworking the software he uses to extend the reach of compliant design.

With the software, and the methodology, twisting its way into more hands, there will be more things in the world with fewer parts.

Michael Abrams is an independent writer.

Learn more about the engineering behind additive manufacturing at ASME Additive Manufacturing+3D Printing – India (AM3D)

Think of a name of an aerospace company—they are already working with us.

Prof. Sridhar Kota, University of Michigan

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February 2015

by Michael Abrams, ASME.org