Gripping without limits

Article of 29 May 2015 

Gripping without limits - adaptive grippers in production

Apples, bananas, grapes: when we go shopping, we reach into the fruit shelves without thinking. Our hands have no problem holding different shapes tightly. In industry it all looks very different: there are indeed already many grippers that are matched to a particular task or product. Gripping devices that are able to adapt to different objects are mostly still the exception, however.

In this respect, flexibility is called for in production, as costs can be thus saved when installations have to be adapted to new products. For several years, Festo has also been dealing with the issue of gripping in the Bionic Learning Network. “The best strategies for adapting come from nature. That is why we are always looking there for new role models that we can transfer to the world of technology,” says Dr. Elias Knubben, head of the bionics team at Festo.

Copied from nature

Festo has already shown how adaptive gripping can work with the FinGripper (2009). It uses the so-called Fin Ray® Effect, which imitates a fish's fin: it adapts to different shaped objects due to its special structure. Adaptive gripper fingers with Fin Ray® Effect were also used in the MultiChoiceGripper (2014), on which the types of grip can also be adjusted, meaning that it is able to grip with its fingers in both a parallel or centric direction – like the human hand. The new FlexShapeGripper, on the other hand, uses a completely new technique to adjust itself: it is literally the chameleon among grippers.

FlexShapeGripper – adaptable like a chameleon's tongue

The chameleon is distinguished by its typical slingshot tongue. The creatures use it both to drink and catch their prey. The tongue is able to adapt to just about any shape and surface finish. The idea of developing a gripper modelled on this was conceived by students at Oslo and Akerhus University College, who work together with Festo in the Bionic Learning Network.

The key element of the FlexShapeGripper is a water-filled silicone cap, which is modelled on the tongue of a chameleon and wraps itself around the item being gripped in a form-fitting manner. “To control it we use a double-acting cylinder, of which one chamber is filled with compressed air whilst the second one is permanently filled with water. The second chamber is fitted with the elastic silicone moulding,” explains Elias Knubben.

The piston, which separates the two chambers from each other, is fastened on the inside of the silicone cap. When gripping, the piston moves upwards, the silicone part pulls itself inwards and wraps itself around one or more objects – because the FlexShapeGripper is able to lift up and put down several objects together at the same time.

Flexible components belong to the future

Adaptive machines and facilities will become increasingly important in future – Elias Knubben is convinced of this fact: “Individual products will be increasingly produced in future. Components like the FlexShapeGripper, which can adapt independently to different products and scenarios, will therefore be indispensable.”

You can see how the FlexShapeGripper works in the following video: