Faster, smoother pneumatic drives

Citation

(2001), "Faster, smoother pneumatic drives", Assembly Automation, Vol. 21 No. 4. https://doi.org/10.1108/aa.2001.03321dad.001

Faster, smoother pneumatic drives

Faster, smoother pneumatic drives

Keywords: Pneumatics, Actuators

Comprising a pneumatic cylinder, displacement encoder and proportional valve – linked via an electronic controller – Festo's new Soft Stop offers quieter, smoother, more accurate and reliable machines, capable of operating up to 30 per cent faster. The secret lies in closed loop controlled deceleration (see Plate 1).

Compared with previous end position control systems, Soft Stop offers important new capabilities. First, in addition to fast traverse between two fixed end stops, actuators can now traverse between two freely selectable intermediate points without fixed stops. Position feedback from the intermediate stops can be used to activate subsequent functions. Second, as well as rodless linear cylinders, Soft Stop can be used with standard linear cylinders.

It is hardly surprising that design engineers constantly strive to develop quicker, faster and more productive machines. However, speed must not be at the expense of accuracy, repeatability and reliability. Driving a cylinder faster is not the issue, controlling its deceleration is.

Traditional pneumatic end position control systems typically comprise two one-way flow control valves, two position sensors, a directional control valve and two shock absorbers. Having served the industry well for decades, this configuration has reached the limit of its capabilities in high frequency, vibration critical applications.

Plate 1 Festo's smart soft stop

Soft Stop offers a solution. In tests, a traditionally damped rodless linear cylinder achieved 13 double strokes in 20 seconds. When fitted with Smart Stop this figure rose to 21 double strokes: and without the need for complex adjustment or programming. In fact, the controller learns the position of the two stops, and frictional effects, when the teach button is pressed. The controller then continuously compares the set-points and actual positions, optimising movement via the proportional directional control valve. Changing operating parameters are automatically compensated for by the controller.

This installation and operational ease also helps reduce costs. Taking this point further, Soft Stop may be the only solution for dangerous or inaccessible applications where conventional manual set-up is simply not possible due to safety reasons.

It is possible to retrofit Soft Stop to existing drives or even replace expensive electromechanical axes with pneumatic alternatives. To assist the design process, Festo offers a planning and configuration programme including Soft Stop selection software which features all relevant calculations.

For further information contact Nicola Meadway, Festo Ltd, Automation House, Harvest Crescent, Ancells Business Park, Fleet, Hampshire GU13 8XP, UK. Tel: +44 (0)1252 775000; Fax: +44 (0)1252 775001; E-mail: nicola_meadway@festo.com