Seven steps to selecting the right air cylinder.
There are many factors that affect the selection of an air cylinder (pneumatic component), so it is important to understand which ones pertain to your application. That way, you can make sure you have the right one for when you need it. The pneumatic component is a vital part of most pneumatics systems and will form the backbone of any project.
In this post we'll walk through a few guidelines for selecting an air cylinder: what size will be best, how long should they last, where can they be found, and more! Along with these factors there are others that will affect your decision as well. This is just a general guideline for determining the right size and type for any application.
What's the purpose?
The first thing to examine when choosing an air cylinder is what the project will be used for. What kind of load will it be supporting? How much weight is it expected to lift? There are two main types of air cylinders: linear actuators and rotary actuators. Each has different uses (and applications) so they'll be better suited depending on your needs. Linear actuators are commonly used in industrial production lines as automated equipment (commonly found in airplanes, semiconductor foundries) or transportation systems like buses. Rotary actuators are used to move heavy loads around, like the "gears" that change the speed of a motor. (Risks: pneumatics components are not made to withstand a load of that magnitude.)
Another important consideration is whether you will be using compressed air or bulk air. The compressor in your existing system, as well as any other components, needs to be compatible with the cylinder you would like to use. If a system already exists, chances are there may already be a cylinder that's compatible and can just be replaced with another one if needed. On the other hand, if you have no existing systems in place there are many cylinders for sale on Amazon or other similar websites. Just make sure to factor in the cost of the cylinder, any required accessories, and shipping costs.
Size
The diameter (or size) of a cylinder will have a significant effect on how much force it can generate. Larger cylinders are able to create higher forces at a lower air pressure. In general, the larger the cylinder, the more definitive and abrupt movements can be made with less energy input. However, for many applications smaller cylinders may be desired due to space constraints or weight restrictions. This is where selecting the correct size comes in.
The table below charts the maximum force values for cylinders of different diameters and length. You'll notice that there is a marked difference between how much force a cylinder of 2 inches can produce (about 39 lbs) versus a 10-inch cylinder (about 88 lbs). The "long" dimension refers to the length of the piston rod, and the "piston travel" refers to distance that it moves each time it is activated.
Cylinder Size Long Dimension (in) Piston Travel (in) Un-loaded Force at 1 PSI Unloaded Force at 5 PSI Unloaded Force at 10 PSI Unloaded Force at 20 PSI 2 inch 0.5 0.8 1.0 1.3 1.5 5 inch 2.0 3.2 3.8 4.3 4 10 inch 5.0 6.8 8.2 9 3 13 inch 7.6 10 13 16 15 20 inch 11 16 24 29 28
Best Seller: The World's Smallest Air Cylinder
The cylinders listed above are the type most commonly used for engineering pneumatics projects because they are readily available, relatively cheap, and work in almost any project you can think of (as long as you can mount them to something). However, there are many more options in the market today if you want to get creative with your application.
The smallest air cylinder (which is also one of the best sellers on Amazon) is the Zano Air Cylinder by Maple Products. It comes out to about 1.5 inches diameter and 0.4 inch thick making it about half the size of a standard air cylinder. It is used for a wide range of applications from weighing coffee beans to powering small projects like a small pump or mechanism on a model car or boat. The cylinder is made of an aluminum alloy and weighs just over a pound.
This size was chosen because smaller-sized cylinders are less likely to be found in existing systems, and sometimes you need only a small amount of force to operate specific components. For example, if you are creating a simple motor for something such as a toy car, you might want to keep the weight light (any air cylinder over one pound is going to cause problems when attached by threading it onto an axle). That's why the Zano Air Cylinder was developed. The cylinder requires an external power source (either DC or AC) with a micro switch that opens and closes the action (once activated by movement or pressure).
How long will it last?
Next, you want to determine the type of cylinder that will be needed for your application. There are two main types: single-acting and double-acting. Single-acting cylinders are the simplest of the two, with only one moving part that allows for movement in one direction. Double-acting cylinders have a second moving part so the piston can move in both directions, which is helpful if you need to retract an object (or force it into a cavity). For example, a device called a gripper uses a pneumatic gripper to handle objects. A gripper uses two arms to pinch whatever it is holding and then releases it when an air cylinder goes back down.
How reliable is it?
Premier Pneumatics manufactures a lot of air cylinders targeted for industrial applications. They have a wide range to choose from, including three different cylinder sizes and other characteristics. The standard size Premier Pneumatics offers is the B46-D5-L. This size is 10 inches long and 2.8 inches thick with a 5 inch long moving rod. The maximum force exerted by these air cylinders ranges from 3 to 14 pounds, but they can be supercharged with an optional pressure regulator to increase their maximum force capabilities up to 35 lbs at 0 PSI.
One of the most important physical characteristics of a cylinder is the strength of the material. The longer and heavier air cylinders are more durable, but not so much if you are working with a model car or other small delicate project. The B46-D5-L has a rating of 16 pounds per square inch (PSI). So how will this air cylinder perform under pressure? Premier says that its standard air cylinders can withstand up to 50 PSI without any problems. Plus, they can withstand up to 45 tons with an optional 15 PSI option. (Source: Premier Pneumatics)
Conclusion
In conclusion, determining which cylinder you'll need for your application is only half the battle.
Conclusion
To answer the question, "what air cylinder is best?" you need to know the forces, locations and amounts of air pressure your application will require. You should track down specs on each cylinder so you can compare them to each other. Also, consider cost, power source requirements and size. Make use of price comparison websites like Amazon or Google Shopping to weigh these factors in comparison to what each company offers for sale.
For more information on air pressure technology get a copy of my book: Stop Worrying! and Learn Pneumatics, a step-by-step guide for learning how to install, operate and repair pneumatics systems in any project.