MOTION SYSTEMS HANDBOOK
Pneumatic
actuators
HOW ARE PNEUMATIC ACTUATORS USED IN AUTOMATED DESIGNS? Pneumatic actuators come in an array of permutations for automation. Rod and rodless actuators are the two most common, though rodless are far more common in the U.S. Rodless actuators include bearings to address moment loads in X. Y, and Z. Tip: Avoid undersized pneumatic actuators for applications by accurately calculating application force; subtracting piston-rod area; accounting for the energy to overcome friction; and accounting for unusual application kinematics. Note that most pneumatic-actuator applications are linear-stroke setups needing two or more position stops. Minimizing stop times in many pneumatic actuators are done by air cushions. Damping seals are another option. Choosing pneumatic actuators over electrical options is common in applications that need motion axes to work without electricity — where sparking poses a problem (as in applications that involve flammable materials for example). Limitations include lack of total controllability and air consumption, but few actuators outperform pneumatic actuators in applications that need clean operation, low upfront cost, and high force-speed ratios. Even so, pneumatic actuators deliver moderate to high load at 120 in./sec or better. Plus advanced pneumatic actuators have wireless valve controls and sensors for IoT and predictivemaintenance functionality.
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DESIGN WORLD — MOTION
Pneumatic Actuators — Motion Control HB 08-19 V3.indd 18
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Festo DGST pneumatic mini slides are compact for precision handling, press fitting, pick and place, and light assembly applications. The DGST slide and yoke plate are machined from a single piece of aluminum for low torsion and accurate alignment. A backlash-free piston-rod-to-yoke connection contributes to the slide’s precision and extended service life. Maintenance free twin piston drives and high force capacity recirculating ball bearing guides provide the DGST with twice the power of other slides — from 7.6 to 132.6 lbf at 6 bar. Cushioning and proximity sensors do not extend beyond the slide’s footprint. Payload is 1.5 to 37.5 lb and stroke from 0.4 to 8 in.
ANOTHER VARIATION ON PNEUMATIC ACTUATION: BLADDERS Bladder actuators are another form of pneumatic actuation for short strokes and constant-force motion. Where appropriate they outperform other systems. In part positioning, footed bladder actuators output consistent lifting force for plates and other wide and flat loads and workpieces. Another application is automatic door seals to work as flood barriers and chamber closures. These inflatable actuators also work in material-handling applications. Such actuators can’t deliver on precision positioning, so only work where designs are forgiving on that parameter. They’re also unsuitable for point-source applications. That said, these actuators are capable of very accurate force control, and strokes can reach a couple inches.
THE BASICS OF ACTUATORS: PNEUMATICALLY OPERATED CYLINDERS Driving linear-motion applications with pneumatic actuators (or air cylinders) is a relatively easy and inexpensive approach. The motioncontroltips.com | designworldonline.com
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