Know Your Pneumatics: Single or Double Acting? Choosing the Right Cylinder

Most pneumatic actuators have a piston and rod that move inside a closed cylinder, which delivers linear motion by moving along a straight line. Various industrial sectors use linear actuators, including packaging, factory automation, and transportation and life sciences.

There are two types of linear actuators: single-acting and double-acting. Typical applications, advantages, and disadvantages of these variations will be discussed.

Single acting cylinders

The thrust or output force of a single acting pneumatic cylinder is limited to one direction. 

Pistons are usually returned by a fitted spring, as well as by weight, mechanical movement, gravity, or an external spring. Compressed air enters the cylinder through a single port, which drives the piston into position.

Single acting cylinders come in two types:

  • ‘Push’ type – the piston is pushed by the application of air pressure.
  • ‘Pull’ type – this type of piston is pulled by applying air pressure.

In applications where only one direction of motion is required, such as clamping, positioning, marking, stroking, and light assembly, single-acting cylinders are used.

 

Advantages:

An elegant design,

Small and compact,

Cost reductions associated with valves and pipes, and

Comparatively to an equivalent double-acting cylinder, the air consumption has been halved.

 

Disadvantages:

On the spring side of the cylinder, it is vented to the atmosphere, which may allow foreign matter inside, which can result in malfunctioning and shortening the life of the cylinder.

The end position of the stroke may be uncertain with spring operation with prolonged cylinder life.

Because of limitations in spring force and size, the cylinder has a limited bore and stroke.

The spring force opposing the thrust causes a slight reduction in thrust.

 

Double-acting cylinders

In a double-acting pneumatic cylinder, the thrust is developed both in the direction of extension and in the direction of retracting. When a load must be moved in both directions, such as opening and closing a gate, double-acting cylinders use high-pressure air to move the piston forward and back by alternating the ports that receive high-pressure air.

During operation, opposite ends of the piston are subjected to alternate air pressure. In the positive stroke (push), air pressure produces a thrust, and in the negative stroke (pull), air pressure produces a thrust.

The use of double-acting cylinders is common where the thrusts and stroke lengths are required to exceed those available from single-acting cylinders. Double-acting cylinders with small pistons are also used when both strokes of the cylinder must be positive at the end of the stroke.

Linear actuators most commonly use double-acting cylinders. Pneumatic control circuits use around 95% of these cylinders.

 

Advantages:

According to ISO standards, double-acting cylinders are the basis for defining standards.

Double-acting cylinders have a wider range of bore and stroke sizes than single-acting cylinders.

Double-acting cylinders are available in a variety of designs.

 

Disadvantages:

In addition to not simply being held in the middle,

In order to reliably feed pneumatic cylinders, they must be coupled to hydraulic slave cylinders to maintain constant pressure, and

The piston rod must be guided adequately in long-stroke cylinders.

 

Pneumatic Cylinder Supplier

Airmax Pneumatics is one of the well known manufacturers, exporters, and suppliers of Pneumatic Cylinders in India. They offer a huge range of pneumatic cylinders including single acting and double acting with a broad range of strokes and bore. Since 1992, they are constantly serving and leading the pneumatic industry in India.

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