Swiss mathematician and physicist Daniel Bernoulli discovered 250 years ago that a partial vacuum is created when a medium such as air flows past an object quickly. The object is not blown away, as expected, but rather sucked in.
Airplanes make use of this elementary effect in fluid dynamics resulting from flowing gases and liquids—it provides them with the lift they need in order to fly. Motorists are familiar with it as well: When quickly passing or being passed by a large truck, air flows quickly between the vehicles, drawing the smaller car or motorcycle towards the truck.
This effect is applied in automation technology with Bernoulli grippers. This method is especially well suited for handling sensitive objects such as silicon wafers—very thin semiconductor wafers that are required for the production of solar cells.
The work pieces are retained by applying overpressure to the gripper. Although air is blown towards the work piece, it’s drawn in because of the Bernoulli Effect, and an extremely small gap is maintained between the work piece and the gripper. Even objects with porous or irregular surfaces can be retained in this way, which would not be possible with a vacuum gripper. This contactless handling technique also prevents permanent deformities of the work piece.
Festo engineers improved the traditional Bernoulli gripper with a flow-optimized design and by taking better advantage of available surface area. These grippers now exert four times the retaining force of other grippers. Noise has also been minimized: The developers have prevented the generation of large, noise-causing air eddies in the gripper with the help of an improved layout. The photovoltaic industry has so far been the primary user of these grippers, but product developers see potential in the handling of carbon fiber mats, carpets, and assembled printed circuit boards.
Guest blog by: Frank Langro, Director–Marketing and Product Management, Festo Corp.
