When to use bellows and diaphragm actuators
Bellows and diaphragm actuators produce force without a piston or sliding seal: a flexible rubber bellows or membrane expands under pressure and pushes against the load. That makes them friction-free, low-maintenance and tolerant of dirt and lateral offset. This guide shows when the drive beats a classic pneumatic cylinder and what to watch for in stroke, force and size.
View bellows and diaphragm actuatorsHow does a bellows or diaphragm actuator work?
Instead of a piston in a tube, a bellows actuator uses a fabric-reinforced rubber convolution between two end plates. Fill it with compressed air and it inflates, pushing the plates apart. A diaphragm actuator uses a flat or rolling membrane that moves a rod over a short stroke. Neither needs a sliding seal, so they run without break-away friction and without lubrication.
Bellows actuator or classic piston cylinder?
A standard piston cylinder delivers constant force over a long stroke and is the right choice for feeding and positioning. A bellows or diaphragm actuator shines with short stroke, high force, misalignment compensation and vibration damping. The force of a bellows actuator is not constant: it drops as the stroke grows because the effective area changes.
- Short stroke with high pressing force: choose a bellows actuator.
- Long, even feed: choose a piston cylinder.
- Vibration isolation or air suspension: double or triple convolution.
- Sensitive clamping or pressing: diaphragm actuator.
How do I size force, stroke and pressure?
Force equals effective area times working pressure and falls across the stroke. So always size the required force for the worst-case stroke position, not the relaxed bellows. Check the maximum allowed working pressure (typically 7 to 8 bar) and the maximum and minimum build height so the bellows is neither over-extended nor crushed.
Read the maker's force curve for the required stroke, not just the peak value.
Compare drivesRespect the minimum and maximum bellows height and plan mechanical stops.
View sizesFrequently asked questions
Why is the force of a bellows actuator not constant?
The effective area of the bellows changes as it expands. Near the retracted position the area, and therefore the force, is greatest, and it falls as the stroke grows. Always size the force for the required stroke position, not for the relaxed bellows.
Can a bellows actuator pull or only push?
Bellows and diaphragm actuators are single-acting and produce pushing force only. Return comes from the load, a spring or an opposing second bellows. For both pull and push on one axis, choose a double-acting piston cylinder.
How long does a rubber bellows last in continuous use?
With clean, dry air, operation within the rated pressure and no over-extension, bellows actuators reach many millions of load cycles. Oil, ozone, sharp edges and over-travel shorten life, so provide air preparation and mechanical end stops.
Find the right bellows or diaphragm actuator
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Force curve, not peak value, for the required stroke.
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