Have you ever seen those pneumatic cylinders at work? They’re used in automatic grocery store doors, truck braking systems, and assembly line machines. These device transform compressed air into linear force.
Simply put: it do the heavy lifting of most industrial tasks. The thing is, uncontrolled movement can create noise and damage parts. Knowing how this little machine works can help you make better decisions when choosing equipment for your own mechanical work.
Knowing how they operate will also help you sidestep some common engineering errors. What makes a cylinder isn’t as simple as “it’s got a piston in a tube.” There are very specific engineering decision made during construction. Well-made cylinders last decades, poorly designed ones fail in months.
Knowing something about mounting options, seal types, and pressures matter. Otherwise, you run the risk of buying overpowered equipment or underestimating the forces at play. By ignoring these aspects, you underestimate what force act upon your device.
These next few sections will describe how each of these work and why certain model are important for certain uses.
Understanding How Pneumatic Cylinders Work
Pneumatic Cylinder Basics
It’s a simple mechanical core. A barrel, two end caps, a piston, and rod form a cylinder.
Ports in the barrel allow compressed air to be supplied. One side of the piston is pushed by the air pressure. That piston then moves forward and back pulling/pushing the rod.
The rod do the work. There are no fancy electronic motors or complex gears. It is just air moving a metal plate.
That’s what makes the manufacturers trust this. The cylinder can be extended and retracted thousands of times per day without wearing out. All you have to do is make sure there is a good regulated air supply.
Dirty air will tear up seals fast. Most commonly, the cylinder is single acting. The air pressure drive the piston in one direction.
Single vs Double Acting Cylinders
In the opposite direction, the piston is returned by a spring. For straightforward ejection or clamping operations, this type of cylinder is fine. Here you have a gentle return and force in one direction.
For more varied applications, double-acting cylinders come into play. In these cylinders, air pressure move the piston back and forth. Because this type of cylinder controls force and speed equally in both directions, it is used to slowely lower heavy objects.
It provides exact modulated control. A spring return will not achieve this level of control. Using the incorrect type of action will result in less than best performance as well as wasted energy.
Mounting Options and Load Handling
Force is transferred to the machine based off mounting options. Clevis brackets, foot mounts, or flanges are used for mounting. Foot mounts stabilize the cylinder from side loads.
Flange mounts give a rigid base for high-force application. Failure to account for mounting style risks bending the piston rod. Bending of the rod indicate failure of the cylinder.
The mechanically weakest part of the cylinder is the rod. Rods bear all the load and they are exposed to elements. Specialized mounts from manufacturers such as SMC and Festo, allow you to fit cylinders in tight spaces.
Match the mount to the stress profile.
Seal Types and Leakage Prevention
Seals retain the air in the cylinder. Keep air out of surrounding area.
Nitrile or polyurethane are common seals used on most cylinders. Polyurethane seals resist abrasions, is durable. Nitrile seals handle oil contamination.
Oil-resistant seals are required if your air system contain oil. Low-friction seals are desired when running dry air. Wrong type of seal will result in leakage or sticking.
Leakage results in reduced holding force and waste of energy. Leakage creates a mess too. Regularly inspecting seals is cheap insurance.
Replace before failure occurs. This saves downtime and avoids pressure drop.
Speed Control with Flow Valves
One important thing to consider is speed control.
Generally speaking, nobody wants a cylinder slamming shut. It makes noise; it damages parts. A solution: adjustable flow control valves that limit the exhaust air to slow down the piston.
The trick is this. You adjust the speed of extension and retraction separately. This is key when doing delicate assembly work, such as placing a microchip using a pneumatic arm.
You want the arm to move quickly but come to a gentle stop. Flow controls provides this level of precision. Otherwise, the cylinder is a blunt instrument.
But with flow controls, it’s a surgical tool. Generally, the flow control valve has a small knob to turn. Turn it, and you change the breathability of the exhaust.
It might feel counter-intuitive. Limiting the exhaust makes the intake slower. Physics, right?
Air Quality and FRL Maintenance
Many people don’t maintain their systems until there’s a problem. Maintaining the system prevents premature failures. Always have regulators and filters before your air goes into the cylinder.
That stuff can ruin a good system. Particles scratch the pistons. Water damages seals and corrodes inside of the barrel.
Use a simple FRL unit. An FRL is a filter, regulator and lubricator. The lubricator sprays a fine mist of oil on the air.
This decreases wear and keeps seals pliable. It is a small cost for a big reward. If you don’t take care of air quality you are damaging the system.
It might function for some time but ultimately seize up. By taking care of the air you keep it regulated and clean. In return you get a reliable cylinder.
Air is a powerful thing when compressed. Moving that air becomes power with a pneumatic cylinder. Those cylinders make sense.
They’re versatile, they perform efficiently, and they last. Knowing what they do will save you both money and time. Select the right mounting style.
Select the proper action type. Using clean air to protect the system. Making the black box come alive.
You will see the mechanics of it all. Recognizing how simple air can be used to move something. How it does move the world.
One push at a time.
