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29 February, 2024

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Tactile gripper is `smaller, cheaper and more powerful` than electric rivals
Published:  18 October, 2007

Festo has developed a flexible, tactile servopneumatic gripper which, it claims, performs better than electrical grippers, but costs about 30% less. The HGPPI gripper integrates mechanical and electronic functions to create a device that is five times more powerful than comparable electric grippers, yet occupies only a fifth of the space.

Festo servopneumatic gripper

The gripper (shown above) incorporates a displacement encoder, control electronics and six piezoelectric valves. It has two jaws that move independently of each other and can thus grip a wide range of shapes, weights and workpiece surfaces. The jaws, which can each exert a force of 50N, have a claimed accuracy of ±0.1mm.

The six 5mm-wide piezo proportional valves that actuate the jaws are powered only during switching movements, thus using minimal energy. The 3/2-way piezo valves generate pressure in the gripper’s cylinders which is monitored by three in-chamber sensors, thus allowing precise control. Because the control and communication hardware are incorporated into the gripper housing, the only external connections needed are to the pneumatic and 24V electrical supply lines, and to a Profibus DP control cable.

The gripper uses standardised mechanical interfaces, allowing it to be integrated easily into customised mechatronic subsystems, such as pick-and-place systems, 3D and linear gantries, and robots. Festo expects the gripper’s flexible operation to open up new ways for handling and assembling small parts.

One pilot customer was the hard drive specialist Xyratex which achieved savings on its disk testing stations by using the HGPPI’s tactile gripping ability to sense the position of workpieces and then to approach them. This cut cycle times and avoided the need for further components to sense position.

Another early adopter, the German custom engineer Axelius Automation is using the gripper in a flexible system for assembling components for automotive climate controls. The system, developed for Behr-Hella Thermocontrol, inserts plugs into panels that are then separated into individual circuit boards.

The gripper positions the plugs over the board and inserts them with a force of 100N per pin. "The proportional gripper can be adapted to different plug dimensions flexibly and without costly conversion", explains Bernd Büsser, project manager for systems engineering at Axelius. "One signal from the system PLC via Profibus is all that’s needed to adapt to different plug dimensions."

"Whereas before we could only insert a specific plug type on a specific panel type on a single assembly line, now we can produce a large number of variants with greater speed and flexibility", adds Peter Stillers, head of planning at Behr-Hella.

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