In control

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Components of varied shape, size and weight can now be produced on a single assembly line, thanks to a new-style servopneumatic proportional gripper. Siobhan Wagner reports

A new servopneumatic proportional gripper with independent jaw movements is making it easier to produce components that range in shape, size and weight — on a single assembly line.

Festo Micro Technology's

HGPPI, which was recently made commercially available in the UK, has the potential to increase the speed and flexibility of assembly operations.

The gripper, introduced in Germany last year, already has a variety of customers, including Behr-Hella Thermocontrol, which uses the device to to produce climate-control systems for vehicles ranging from sports cars to people carriers.

Climate control technologies can differ greatly depending on the vehicle, but the HGPPI gripper is able to insert plugs into panels for any type of system on the same assembly line.

'Before, we could only insert a specific plug type on a specific panel type on a line, but now we can produce a number of variants with more speed and flexibility,' said Peter Stillers, head of planning at Behr-Hella's Lippstadt headquarters.

The gripper features a pair of parallel slide-mounted jaws that operate independently — both in terms of position and force. Three air chambers, each with its own pressure sensor, pneumatically drive the slides.

Airflow is controlled in the chambers with a set of six 5mm-wide, 3/2-way piezo valves developed by Festo in Switzerland. These valves contain a bending piezo actuator that uses micrometre-scale deflections to open and close the valve ports. The piezo technology is only powered during the switching movement, which means manufacturers can achieve better energy savings.

The gripper integrates the electronics and sensors to control position and force with a precision of +/-0.1mm and +/-2.5N. Each jaw covers a gripping force ranging from five to 60.

While piezo actuators have been used to directly manipulate tiny loads for years, this is the first time they've been used as part of a larger servopneumatic system, and the gripper is Festo's first commercial product to use them.

Once the the gripper has inserted the plugs into panels, they are then separated into individual circuit boards, tested on the in-circuit tester and packaged for final assembly into a climate control system.

The gripper positions the plug over the circuit board and holds it before inserting it into panels with a force of 100n per plug and can be simply adapted to different plug dimensions with a signal from the system's programmable logic controller (PLC) via Profibus.

According to the company, the gripper is 30 per cent less expensive than comparable electrical ones because there are no additional costs for the controller, which is already integrated in the technology as a complete mechatronic system.

Also, it is able to produce forces that are five times more powerful — and it takes up only 20 per cent of an electronic gripper's space.

With standard mechanical interfaces, the device can be integrated in customised mechatronic subsystems such as pick-and-place systems, linear and 3D gantries, and robots.

Sven Zybell, director of Festo's microtechnology operation, said the gripper's features are becoming standard at the company, which is currently working on more microtechnology-based automation technologies.

He said the combination of mechatronics and microtechnology results in systems that take up less space, use a fraction of the energy and often perform better than classical mechanical systems. 'Smaller, smarter and more integrated — that's the way forward,' he said.