Compliant Robot Gripper Won’t Scramble Your Eggs

gripper

[Chiprobot] has created an amazing compliant gripper.  Designing robot hands (or end effectors) can be a perilous task. It is easy to give robots big, good, strong hands. Strong grippers have to be controlled by sensors. However, sensors can’t always be relied upon to ensure those hands don’t crush anything they touch. Hardware fails, software has bugs. Sometimes the best solution is a clever mechanical design, one which ensures a gripper will conform to the object it is gripping. We’ve seen “jamming” grippers before. (so named for their use of a granular substance which jams around the object being gripped).

[Chiprobot’s] gripper is something entirely different. He designed his gripper in blender, and printed it out with his Ultimaker 3D printer. The material is flexible PLA. Three plastic “fingers” wrap around the object being gripped. The fingers are made up of two strips of printed plastic connected by wire linkages. The flexible plastic of the fingers create a leaf spring design. The fingers are attached to a linear actuator at the center point of the gripper. The linear actuator itself is another great hack. [Chiprobot] created it from a servo and an empty glue stick.  As the linear actuator is pulled in, the fingers pull around  any object in their grip. The end result is a grip strong enough to hold an egg while shaking it, but not strong enough to break the egg.

We would like to see the gripper gripping other objects, as eggs can be surprisingly strong. We’ve all seen the physics trick where squeezing an egg with bare hands doesn’t break it, yet squeezing an egg while wearing a ring causes it to crack much… like an egg.

22 thoughts on “Compliant Robot Gripper Won’t Scramble Your Eggs

    1. I work at Festo but I never really understood why it would be necessary to print the braces inside the “fingers”.
      It only makes the design more complicated and you can’t use a FDM-based printer.
      So I would say this is a really clever adaption to the original design. And an improvement in manufacture.

      1. Yes you are right but if you have a SLS Printer its more easy to print the Braces between the fingers. I think they add some limits to the structure to avoid beaking of the outer elements and makes the gripper more durable.

    2. The first time I saw the principle was on a TV show where they presented a chair with a back rest working that way. Quite a neat trick. The hacker sees the concept and applies it to whatever he seems fit :)

  1. I appreciate his remake, but first he have to master the 3D-printed pneumatic piston design on the bottom of the gripper. The most difficult part on this design – greetz from Festo developer

    Btw. at all interested people -the Fingripper (this Gripper without drive) is very easy to remake out of paper with the same function.

  2. I’m hoping that some day I will make a robot to pick up fallen apples or even apples from the tree, this would be perfect for it. Though I guess the remaining parts would be much more work than this anyway :).

  3. if you made a three-fingered rubber glove to fit over that and you could combine this design and the jamming gripper concept. when the pressure in the glove is equalized the mechanical fingers can manipulate its shape, then a vacuum will lock the hand in place

  4. Skip making the pnematic piston on a 3d printer and just use a good old plastic syringe? maybe print your own plunger to work with the rubber stopper so you replace the end where your thumb would normally press into something of a better mechanical interface to mate with the gripper. But the servo is much better (imho) because it takes pneumatics out of the picture altogether, which end up being controlled by electronics in the end anyway. Kind of complex and redundant…

  5. Gareth didn’t really have a reason to put this in his LMR post, but he was completely aware of the Festo design as it was mentioned originally in another thread:http://letsmakerobots.com/node/39140, where I more or less begged one of our members with the resources to attempt it. However, as we learned subsequently, there were others doing work with similar designs before the Festo version. See http://letsmakerobots.com/node/39387#comment-111114. Still, his implementation is unique and innovative. Also, as the video in the link points out, the idea came from nature. Criticizing the maker for copying a commercial design that was in itself copied from the bodies of fish is a little odd, isn’t it?

  6. This would be really useful in automating farms that rely primarily on hand pickers. Lay some rails between the rows and the pickers could ride them and push/pull a hopper. The picking gripper could be coupled with a camera and or color measuring tool at the end of the picking arm. The picker bot would follow the veteran human pickers along as they examined and picked ripe produce. The human would hand the ripe item to the bot for it to learn what was ripe and thus establishing a set of parameters. The same goes for the bad/rotten stuff. I don’t know how it would work with grapes but I think adaptations could be made.

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