In a pneumatic cylinder, the compressed air is used to exert force on a cylinder piston in order move it in a specific direction. The movement of the piston is transferred to the parts to be moved by a piston rod or a frictional connection. A pneumatic cylinder is a drive operated with compressed air usually up to a maximum of 12 bar in order to generate linear or rotary motion. A distinction should be made between single-acting and double-acting cylinders (work is performed only in one direction or in both directions).

A single-acting pneumatic cylinder only has one compressed air connection. The incoming compressed air moves the piston in one direction, and the cylinder force is built up in this direction. If the piston needs to return to its initial position, the air is simply expelled from the cylinder. The mechanical spring pushes the piston back to its initial position. This part has a ventilation/exhaust hole so that no excess or low pressure is generated through the piston movement in the second cylinder chamber.

Benefits:

• Defined position in the event of a power failure
• Reduced air consumption
• Easy actuation via 3/2-way valve

Disadvantages:

• The cylinder design is longer
• Spring-dependent stroke length limits the maximum stroke length
• Force is only built up in one direction
• Force is reduced by the spring force
• No constant force (stroke-dependent)

The double-acting cylinder requires compressed air for every direction of movement. On this type of cylinder, the force in both the advancing and retracting direction is built up using compressed air. The simplest way of actuating a double-acting cylinder is by using a 5/2-way valve.

Benefits:

• Force builds up in both directions of movement
• Constant force (dependent on stroke)
• Strokes of several metres are possible

Disadvantages:

• Every movement uses compressed air
• No defined position in the event of compressed air failure