What can system designers do to help pneumatic actuators attain maximum speed?

Phil/Bosch: Optimized speed and adequate cushioning at end of stroke requires different pressures to extend and retract the cylinder. For example, a cylinder retracted with 25 psi and extended with 90 psi will only have to exhaust 25 psi when the cylinder extends. Higher differential pressure across the piston corresponds to faster breakaway and higher steady state speed. Higher speeds can also be achieved using two valves. A second valve that reverses the pressure applied to the directional control valve can optimize speed in both directions, provided there is sufficient time for the reversed pressures to reach their nominal values before the cylinder is cycled again.

Walt/PHD: Many pneumatic actuators are designed for power and motion, but not necessarily for carrying a load. Precautions should be taken to ensure that the load is handled through the use of bearings or guides. For this reason, many suppliers provide actuators with bearings, creating devices such as linear slides, grippers, escapements, and rotary actuators. Each of these are equipped with varying types of bearing systems with recommended load and speed requirements.

Gary/Beswick: Designers should consider the number of fittings, tubing lengths, and valves. These components should be sized to minimize pressure losses upon actuation. Fittings should have the largest orifice possible for maximum flow. Thread sizes on fittings should be large enough to allow a passageway of the same inner diameter of the tubing being used. Rigid metallic tubing should be used over flexible tubing. Quick relief fittings can be used advantageously to exhaust air close to the actuator. Other components of interest include mufflers and valves. Mufflers should not have a significant pressure drop. Valves should have a fast response to the control signal as well as high Cv values. They should also be placed as close to the actuator port as possible (mounting on the port itself is ideal). Supply pressures should be as high as possible. Supply airlines should also be examined to eliminate pressure starvation of the control system.

Frank/Festo: High piston speed translates to high kinetic energy. To prevent this from causing problems, you have to slow the piston before it impacts the cylinder end caps, causing premature failure. Without considering this in your design it's possible that the piston and rod could detach. Another consideration is heat build-up. You have to consider how this could affect elastomeric seals used inside the cylinder or any thread locking compound used throughout.

For more information, contact the editor at mgannon@penton.com