Single or double-acting pneumatic cylinders: which do you need and why?

Pneumatic cylinders offer a cost-effective and maintenance-free solution for generating force and motion to power a wide range of automation applications. There are two main types: single-acting cylinders, which feature one port and double-acting cylinders, which have two. The question is, which one do you need and why?

API UK explains the basic functions, advantages and disadvantages of both types of cylinders to help you make an informed choice. Read on to find out more.

HOW DO PNEUMATIC CYLINDERS WORK?

Pneumatic cylinders, or pneumatic actuators as they’re also known, provide automated systems and machines with linear or rotary motion and force. Essentially, compressed air is forced into the cylinder to move a piston within it. A mechanism attached to the piston then harnesses that energy and puts it to good work in the specific application. For instance, an automated picking and placing system in a factory.

Pneumatic cylinders provide a simple solution for generating force and motion, even in the most challenging operational environments. Not only are they lightweight, but they also require very little maintenance. Of course, compared to hydraulic and electric systems pneumatic cylinders produce slower speeds and less force but, wherever these aren’t such a priority, they offer a highly cost-effective alternative.

SINGLE-ACTING PNEUMATIC CYLINDERS

In a single-acting pneumatic cylinder, when compressed enters the rod moves in one direction only. The high pressure of the compressed air causes the rod to extend as the cylinder chamber continues to fill. When the compressed air leaves the cylinder through the same port the rod is returned to its original position.

Most commonly, the rod returns to its original positioning due to an internal spring. As the pressure lessens, the spring simply pulls the rod back. There are other options with returning the rod in a single-acting cylinder back to its default position. These are an external spring, the weight within the system or simply gravity.

Single acting cylinders are typically employed in applications requiring work to be done in one direction only, such as positioning, clamping, marking, stroking and light assembly operations.

ADVANTAGES OF A SINGLE-ACTING PNEUMATIC CYLINDER

Compact size
Simple design
Reduced valve and piping costs
Air consumption half that of a double-acting cylinder

DISADVANTAGES OF A SINGLE-ACTING PNEUMATIC CYLINDER

Restricted bore size and stroke
Opposing spring force reduces thrust
Spring operation can become inconsistent
Ingress of foreign matter can cause damage

WHAT IS A DOUBLE-ACTING PNEUMATIC CYLINDER?

With a double-acting pneumatic cylinder, there are two ports controlling the movement of the rod. The compressed air causes the rod to move in two directions by extending and retracting, making a double-acting pneumatic cylinder essential for any applications requiring control of movement in two directions without the need for a spring.

Double-acting cylinders are the most commonly installed type of linear actuator, accounting for around 95% of all cylinders employed in pneumatic control circuits.

ADVANTAGES OF A DOUBLE-ACTING PNEUMATIC CYLINDER

ISO standards based on double-acting cylinders
More bore and stroke size options
Lots of variations of basic double-acting cylinders

DISADVANTAGES OF A DOUBLE-ACTING PNEUMATIC CYLINDER

Needs a hydraulic slave cylinder for use as a feed cylinder
Adequate guiding of piston rod required for long-stroke cylinders

SINGLE AND DOUBLE-ACTING CYLINDERS FROM API PNEUMATIC UK

Now you know the basic functions, advantages and disadvantages of single and double-acting pneumatic cylinders, you should be much better placed to select an appropriate pneumatic cylinder for your application. Of course, should you require an extra helping hand, API UK’s friendly and knowledgeable pneumatic experts will be only too happy to guide you towards the most appropriate cylinder for your needs.

We manufacture and supply the following types of pneumatic cylinders:

For help and guidance with your pneumatic cylinder selection, contact our technical team today. We are more than happy to advise you on the most suitable cylinder for your requirements. Call 01782 206 995 or email [email protected].