Soft two-finger gripper

Print your own youBot Gripper

The standard KUKA youBot gripper is designed for small objects like cubes or bars. It has a stroke of 20 mm and the design of fingers is optimized for these kinds of objects. However, in case you need to grasp round objects, the standard fingers are too short and stiff in order to these objects properly. These shortcomings are avoided by Festo FinGrippers(R) (http://www.festo.com/cms/de_corp/9779.htm) as shown in the following video (https://www.youtube.com/watch?v=90cXfaFM4O8). FinGrippers are flexible and long enough to grasp a large variety of objects. This motivated the RoboCup team at Bonn-Rhine-Sieg University of Applied Sciences to design a new two-finger gripper. The design uses the youBot's original two-finger drive but instead of the rigid fingers uses Festo's FingGrippers actuated over a smart parallel mechanism. It does not require any new electronics or control software.

The result is a lightweight mechanical structure that can be printed by a 3D printer (besides the metal axes). The mechanics have already been used for several months in the research group at Bonn-Rhine-Sieg University of Applied Sciences (http://www.mas.inf.h-brs.de) and by their RoboCup Team b-it-bots (http://www.b-it-bots.de/) in the German Open RoboCup@Work competition (http://www.robocupgermanopen.de/, http://www.robocupatwork.org/).
They would like to share their design with the youBot community and thus publish the CAD files as “open source”.

Every developer is welcome to modify and improve the design in case they have any further ideas. The Bonn-Rhine-Sieg University team would be glad if other developers would publish their new designs as well.

You can download the data (CAD drawings & description) here.

You can buy a fully assembled gripper here. 

Note: We observed that the friction in the axes very much depends on the accuracy of the 3D printer. If the holes are slightly too small, the friction is too high and the KUKA youBot gripper motors will not be able to move the gripper at all. In that case, you can (1) try to move the gripper mechanics manually about 10-20, hoping that this will reduce the friction or (2) slightly drill up the holes in the printed parts. 

Credits
Matthias Füller, Frederik Hegger, Erik Solda (firstname.lastname at h-brs.de)