What are Pneumatic Cylinders?

Pneumatic cylinders are mechanical devices that produce force by using energy from pressurized air. These devices consist of a piston, piston rod, and cylinder. The pressure inside the cylinder rises as air enters on .one side of the cylinder. The rise in internal pressure causes the piston to move in a specific direction. The piston rod transmits the developed force to the object to be moved. A double-acting cylinder uses compressed air to move a piston in and out, while a single-acting cylinder uses compressed air for one-way movement and a return spring for the other. They have numerous accessories, like sensors to detect the position of the piston and different mounting accessories to mount the cylinder or add components to the end of the piston. A wide range of industries requiring linear motion use pneumatic cylinders since they are simple to use and are a cost-efficient solution. They are also referred to as air cylinders.

Double-acting pneumatic cylinder

Double-acting pneumatic cylinders are the most common type since they give the user complete control of the piston movement. A negative position is when the piston rod is retracted, and a positive position is when the piston rod is extended. When compressed air enters the cap-end port, it pushes the piston forward (positively), extending the piston rod. Air is forced out of the rod-end port. To retract the piston rod, compressed air enters the rod-end port, forcing air out of the cap-end port, and forcing the piston to retract to the negative position. Double-acting pneumatic cylinders allow the user full control, longer piston stroke length, and a constant output force through the entire stroke. They can also operate at higher cycling rates. However, a double-acting cylinder should not be used if the application requires a base position during fail-safe scenarios encase there is a loss in compressed air. Since they use compressed air for both directions, they also use more energy

Single-acting pneumatic cylinder

A single-acting pneumatic cylinder only uses compressed air to drive the piston in one direction. A mechanical spring moves the piston in the opposite direction. Either the spring extends or retracts the piston. Single-acting cylinders are often used for fail-safe applications where it is required that the piston is in a certain position upon compressed air loss. Therefore, single-acting pneumatic cylinders have a “base” position. Due to the mechanical spring, single-acting pneumatic cylinders do not provide a consistent output force throughout the full piston stroke length due to the opposing spring force. Furthermore, the stroke of single-acting cylinders is limited due to the space of the compressed spring. Therefore, the construction length of single-acting cylinders is longer than the actual stroke length.

Cushioning

The movement of the piston in a pneumatic cylinder can be very fast as the compressed air enters the cylinder. This fast movement can create a hard shock when the piston hits the head or end cap. This shock imposes stress on the air cylinder components, makes a noise, and transmits vibration to the machine structure. To prevent this, cushioning at the caps is used to decelerate the piston. Cushioning can also prevent the piston from rebounding (bouncing) off the end position.