Avoiding mistakes in choosing pneumatic cylinders

To the uninitiated, selecting the right pneumatic cylinder for your chosen application can be quite a complex process. Pneumatic cylinders are used in a variety of applications and industries, come in thousands of variations, and feature an even wider range of components. Each pneumatic cylinder type has unique specifications and can also be manufactured from a host of different materials to suit different working environments and OEM equipment. With all this in mind, it’s understandable that you might get bewildered when first trying to discover the right pneumatic cylinder to meet applications precise requirements.

But fear not, as it just so happens that API Pneumatic UK is a specialist in all things pneumatics. As such, we’ve decided to share our years of industry knowledge and expertise by providing some useful guidelines for first-time customers. Here are some of the common mistakes that you should avoid when choosing pneumatic cylinders for your application.

How to improve your pneumatic cylinder selection

The first thing to understand is that there is no one industry recognised criteria for pneumatic cylinder selection. Instead, there are several individual factors that frequently appear within multiple purchasing guidelines among manufacturers, engineers and industry experts alike.

These include:

  • Consider the mass of the item to be actuated
  • Available air pressure
  • The distance the object has to move (stroke length)
  • The envelope within which the cylinder is to operate
  • Consider any possible side loading and look at mounting options to avoid it
  • The speed of actuation must be established
  • Will the cylinder travel be stopped by external, mechanical stops, or rely on the cylinder end caps for end positioning
  • The environment within which the cylinder will operate (corrosive and/or extreme temperatures)

Choosing the right pneumatic cylinder design

With thousands of variations available on the market, knowing your precise pneumatic cylinder requirements can be quite overwhelming. Which is why you should begin with choosing the right pneumatic cylinder design and work from there. The most standard pneumatic cylinder design available on the market is a rod-style cylinder. These come in two distinct variants; single-acting and double-acting pneumatic cylinders.

Single-acting pneumatic cylinders are used to deliver motion in one direction only, whereas double-acting pneumatic cylinders are capable of providing both forward and backwards motions. Which is most beneficial to your application should be the first deciding factor you should make with your pneumatic cylinder selection.

Once you’ve decided on whether you require a single or double-acting pneumatic cylinder, you begin to narrow down what type of rod-style cylinder design is best for your application requirements. For example, repairable pneumatic cylinders can generally be used in heavy-duty applications due to the ability to replace seals and internal components, thereby prolonging cylinder lifespan. By comparison, lighter-duty applications tend to use disposable cylinders, as they cost less to manufacture but must be replaced more often due to their permanently sealed design.

Compact pneumatic cylinders might be preferred for smaller spaces, where short strokes are preferable. Guided cylinders are recommended for applications with either sizeable offset loads or for loads that require precise direction. Finally, rack and pinion style (or rotary) pneumatic cylinders are used to operate quarter-turn valves, often a requirement for applications found within the process industry. Rod-style pneumatic cylinders might be the most common design on the market, but rodless cylinders are also available for applications with either long stroke or high moment load requirements.

Understanding the performance of your chosen pneumatic cylinder

After you have narrowed down your pneumatic cylinder selection, the next thing you’ll want to consider is performance. Each pneumatic cylinder type is capable of varying degrees of performance, so you’ll need to be sure these qualities align with your application type for the best possible results. The three things to measure when assessing the performance of pneumatic cylinders is force output, speed and air consumption.

Force output can be determined from the air pressure and bore size of a pneumatic cylinder. The general rule of thumb to be used when examing force output is that any force generated by the cylinder should be twice as much as the load. Stroking speed of a cylinder can be determined by dividing the airflow in standard cubic feet per minute by the piston area. For a simpler analysis, look at things like port sizes, inlet, tubing sizes and exhaust flow through control valves.

Pneumatic cylinder consumption has two factors: the volume of air displaced by the piston during operation and the volume of contaminated air that passes through valves, ports, tubing and cavities. If your chosen pneumatic cylinder can supply air even in a worst-case scenario, then optimal performance should be a guarantee for your chosen application.

Additional considerations for pneumatic cylinder selection

Whilst design and performance are the primary considerations for avoiding selection mistakes, there are other factors that could potentially influence your decision. The environment of your application can play a huge factor in the choice of your pneumatic cylinder. Pay close attention to the cylinder and seal materials of your pneumatic cylinder because some (such as stainless steel cylinders) will offer better performance than others. This is particularly important when choosing pneumatic cylinders for applications with extreme temperatures or strict hygienic process requirements.

We would also advise looking at the mounting configurations of your chosen pneumatic cylinder. These refer to how the cylinder attaches to adjacent equipment. Standard mountings traditionally ensure cylinders can execute specific movements that your application requires. Position feedback and cushioning are also factors that you might want to consider, as both can influence what type of performance a cylinder might be able to deliver. For example, magnetic cylinders are capable of different types of position feedback when compared to non-magnetic cylinders. Cylinders with cushioning can prevent damaging metal-to-metal contact with end covers, which would normally result in potential mechanical damage.

Adding his thoughts on how customers should choose a pneumatic cylinder, Tim Swift of API UK had this to say: “With all the above taken into consideration, if the load to be moved relies upon the full cylinder stroke and end caps for positioning, cylinders with internal pneumatic cushioning will be required. In this instance, standard ISO 15552 cylinders would be suitable.

“For clamping applications, end of stroke cushioning may not be required, as the workpiece will terminate the rod travel. In this instance, compact cylinders would be suitable. Any sideload, no matter how slight, would require a guided type cylinder to take up the side load and prolong the life of the piston rod neck seals.

“In clamping applications, with a short-stroke cylinder may be preferable to double acting, as the piston rod will remain retracted upon loss of air. Any rotary motion would require the use of a rotary cylinder. In cases of restricted access, or long stroke, where the positioning of the cylinder body extends the machine envelope, rodless cylinders should be considered”.

Buy pneumatic cylinders from API UK

Pneumatic cylinders are widely used to generate force and motion in OEM applications because they are simple, economical, durable and easy to install. They are capable of producing force over a broad range of velocities, high cycle speeds without overheating, stall without internal damage, and tolerate tough operating conditions.

Applications where you might require the use of a pneumatic cylinder include:

  • Any application where the movement of a load is required
  • Food machinery, for positioning product
  • Conveying equipment, divert chutes, reject pushers, stop cylinders
  • Opening and closing sliding doors on process machinery
  • Safety interlocks on access doors
  • Clamping of workpieces
  • Pneumatic presses
  • Assembly fixtures
  • Robotic manipulation
  • Opening and closing of process valves
  • Safety shut off circuits in hazardous environments
  • Pneumatic lifting equipment

API UK has one of the most extensive portfolios of pneumatic cylinders, accessories and components available anywhere on the market. We can match the right pneumatic cylinder type with your desired application or process. Browse our pneumatic cylinder selection online or speak to our team directly about your application requirements by calling 01782 206 995 or email sales@apiuk.co.uk.