Pneumatic Cylinder Cushioning Explained

Pneumatic cylinder cushioning reduces the impact created when the piston reaches the end of its stroke.

Without suitable cushioning, a fast-moving piston or heavy external load can strike the end cover with excessive energy. This can increase noise, vibration and wear or damage the cylinder and surrounding machinery.

Why cushioning is needed

Cushioning may be required to:

• Reduce end-of-stroke impact
• Lower operating noise
• Protect cylinder components
• Reduce vibration in the machine
• Support higher operating speeds
• Improve movement quality

Elastic cushioning

Elastic cushioning uses an internal resilient element to absorb some of the piston energy at the end of the stroke.

It is often suitable for lighter loads, lower speeds and compact cylinders where adjustable pneumatic cushioning is unnecessary or unavailable.

Fixed pneumatic cushioning

Fixed pneumatic cushioning restricts the exhaust air near the end of the stroke using a manufacturer-defined internal arrangement.

It provides a set cushioning characteristic without an external adjustment screw.

Adjustable pneumatic cushioning

Adjustable cushioning uses a cushioning seal and an adjustable exhaust restriction near the end of the cylinder stroke.

As the piston enters the cushioning zone, the normal exhaust route is restricted. The remaining air is forced through the adjustable cushioning passage, slowing the piston before it reaches the end cover.

How cushioning is adjusted

The adjustment should slow the piston smoothly without causing it to stop abruptly before the end position or rebound from excessive trapped pressure.

Adjust in small increments and observe the movement through repeated cycles. Follow the cylinder manufacturer’s adjustment procedure where available.

Cushioning is not the same as speed control

Flow control valves regulate cylinder speed through the main movement. Cushioning controls deceleration near the end of the stroke.

A cylinder can still strike heavily at the end of its travel if the general operating speed is too high for the load, even when cushioning is fitted.

External shock absorbers

High-speed, high-mass or demanding positioning applications may require an external industrial shock absorber or another mechanical deceleration system.

The pneumatic cylinder cushioning should not be expected to absorb energy beyond the manufacturer’s stated limits.

Common cushioning problems

• Cylinder reaches the end position too aggressively
• Cylinder stops before completing the stroke
• Piston bounces at the end position
• Cushioning screw is fully closed
• Cushioning seal is worn or damaged
• Load or speed exceeds the cylinder capability
• Exhaust flow control is incorrectly adjusted

Replacement considerations

When replacing a cylinder, check whether the original uses fixed cushioning, adjustable cushioning or elastic bumpers. A cylinder with the same bore and stroke may behave differently if its cushioning arrangement changes.

See the pneumatic cylinder replacement guide or browse all pneumatic cylinders.