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Gripper like a hand.

"FLEXIBLE" IS A WORD NOT USUALLY ASSOCIATED WITH ROBOTIC GRIPPERS, AND FOR GOOD REASON. Robotic grippers can open and close their jaws and rotate all they want, but most are engineered to pick up only one specific part fixtured in one predefined orientation. No one would confuse this with a truly flexible gripper--your hand, for example--that can clasp and manipulate objects as diverse as a penny, a ball, or a fork.


Festo AG's new FinGripper shows one new approach to changing this paradigm. The company put it on display at Germany's Hanover Fair this past April. Despite being surrounded by swimming and flying robotic penguins, the FinGripper drew a large crowd of engineers.

What they saw were the three plastic "fingers" that made up FinGripper's hand wrapping around each of three differently shaped light bulbs, and lifting and rotating them 90 degrees. The gripper had a touch so light it could manipulate the fragile bulbs without breaking any glass, and so flexible it could grasp one disparate shape after the other.

The key to FinGripper's performance is the "Fin Ray" structure of its three "fingers," which move like the flexible tail of a fish. (This is something Festo learned from studying how penguins and fish swim.)

Each FinGripper finger looks like an elongated isosceles triangle with a series of slats running between the two long sides. The slats are attached to the side with hinges, which act like bearings. When the triangular finger wraps around an object, such as a light bulb, the slats pivot to accommodate the motion while providing the reinforcement needed for a firm grip.

Festo made the grippers directly form CAD drawings using selective laser sintering, which fuses one layer of plastic at a time until the structure is complete. The company powers the three fingers with a pneumatic bellows.

"We haven't optimized the design yet," said Markus Fischer, a Festo designer who leads the company's efforts to translate biological capabilities into industrial applications. "We thought it would break after 10,000 to 100,000 cycles, but so far it has lasted 5 million cycles."

Like natural systems, Festo's FinGrippers have evolved. "The grippers either worked as a system or not at all," Fischer said. "The first ones we printed out were not so good. They needed thicker walls and bearings on the strips going across."

Festo wants to use the technology for industrial robotics, said Fischer. Potential applications include aquaculture and agriculture, where the FinGripper could sort fragile objects like tomatoes.

This section was edited by Associate Editor Alan S. Brown.

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Title Annotation:TECH FOCUS: Materials and Assembly; Festo AG und Co.
Author:Brown, Alan S.
Publication:Mechanical Engineering-CIME
Date:Sep 1, 2009
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