Pneumatic cylinders are popular due to their simplicity, long life, cost-efficiency, and ease of installation and maintenance. They produce a large amount of force over a wide range of speeds. Maintain high speeds without overheating, and suffer no damage if they stall. Further, pneumatic cylinders are robust enough to work in extreme conditions. Such as dirty and dusty environments, high-pressure washdowns, high humidity, and explosive environments.
Despite this versatility, it can be difficult to pick the right type of actuator. For a particular application; a few key points must be considered.
Pneumatic Cylinders Types
When choosing pneumatic cylinders, the first distinction is whether they are piston rod actuated. A single-action rod type uses compressed air to move the piston rod. With one stroke moving the load and an exhaust port letting the air out. Depending on the speed of the exhaust port, the rod moves at a different speed. A double-acting cylinder drives the rod back again. Allowing a push-pull load, whereas a single-acting cylinder uses a return spring.
Rod-style cylinders can be further divided into different types:
- Compact, for tight spaces and short strokes. Mostly single-action.
- Durable and repairable for longer service life
- Disposable, less-intensive operations with no potential for repair
- For controlled, precise linear motion and high side loads
- Rack-and-pinion to convert linear motion into rotation
Various types of cylinders without rods are available, such as bellows-type cylinders. With an inflatable elastomer tube that produces a high force and bends in any direction. A linear sliders with a carriage-mounted or cable-and-pulley load. Additionally, there are magnetically coupled actuators and guided linear slides. For high moment loads or applications requiring a long stroke, pneumatic cylinder is ideal. They also save space by containing the stroke action within the overall envelope.
Stroke of Pneumatic Cylinders
By determining the stroke length, the type of cylinder needed can be narrowed down. Generally, stroke length depends on the job. Overlaps may occur, but here are some general categories:
- For compact cylinders, as little as 1/16″ stroke
- With an intermediate stroke, up to 3 feet in length
- An automatic door with a long stroke (e.g., 40-99″)
- Special stroke, pulling a piston up to 15-25 feet with a cable and clamp
It is possible to place cable cylinders remotely. As the cable can be any length that suits the application and mounting requirements.
Force of Pneumatic Cylinders
The force the cylinder needs to generate for your application is another important consideration. When choosing a pneumatic cylinder. For push force, the internal dimensions or bore size of the cylinder, and the air pressure can be calculated. Pull force is calculated by reducing the bore size by the cross-section of the piston rod.
There is therefore an equation for theoretical push force:
(Air Pressure) x (Bore Size) = Force
Power Factor = Force ÷ (Pressure Applied)
A margin of safety should be included, so for a safety factor of 50%, our cylinder power factor should be multiplied by 1.5 and the cylinder bore should be calculated based on this result.
If (Bore Size) x 1.5, then *(Bore)2 ÷ 4.
As a general rule of thumb, for high-friction and vertical applications. The force required will be twice as much as the load, but sometimes additional force is required to compensate for excessive friction. When spring returns are involved, calculations can also be complicated by push and pull factors, but manufacturers’ catalogs usually include tables for easy reference. Use our cylinder sizing calculator.
Alternatively, you can use the force tables provided by manufacturers in their catalogs. We also list the values in our product data fields.
Speed of Pneumatic Cylinders
Speed affects how well you can control your load, as well as how long and productive the cylinder will last. A pneumatic cylinder’s stroke speed can be calculated using the following formula:
Wheres = 28.8q/A
s = the speed in inches per second
q = the airflow in cubic feet per minute
A = piston surface area in square inches
The speed of a pump can also be affected by other factors, such as the size of the ports, the length of the hoses or tubing, or the flow rate from the inlet and exhaust valves. There can be bottlenecks in the flow of air into or out of the cylinder, which will reduce the air pressure and slow the cylinder down.
Air consumption by Pneumatic Cylinders
For fast-cycling applications, it’s often necessary to carefully calculate the cylinder’s air consumption, in order to make sure that there will be enough air available. Even in worst-case scenarios, your compressor needs to have the capacity to supply your pneumatic equipment, as air starvation at a critical moment can adversely affect performance.
Mounting
The mounting configuration describes how a cylinder is attached to the equipment. Several standard mountings are available, both rigid and articulated, making it easier to meet your application’s specific movement requirements. It is possible to modify the style of the cylinder if the mounting hardware does not match your desired mounting position, but commissioning unique hardware will cause delays and raise the cost.
Material of Pneumatic Cylinders
Brass, steel, stainless steel, aluminum, engineered polymers, or a combination of several materials are often used for pneumatic cylinders. The choice of material will depend on the operational environment. The same is true for seal materials, but alternatives can be specified for hazardous environments.
Custom Actuators
You may need a custom design if standard components are insufficient. A new configuration may be devised for standard or modified components, or a new unit may be invented. It might be a good choice if you are interested in high levels of efficiency, complex motion control, or components that don’t currently fit standard combinations. Nowadays, intelligent design is able to incorporate specialized configurations and will produce custom products that are perfectly tailored to your needs.
Conclusion
There are clearly many factors that can influence your decision. Furthermore, there are various factors such as load positions, sensors, temperature requirements, and any special movements that require modified cylinders. Magnetic cylinders have positioning feedback controls, as well as cushions or shock absorbers to reduce noise and impact.
It makes sense to select a pneumatic cylinder carefully since it accounts for a significant part of your installation budget. Ultimately, it’s always best to speak with a manufacturer or a technical sales engineer about your specific needs. Airmax Pneuamtics Ltd is a leading pneumatic valve supplier in India. They also offer various types of pneumatic air cylinders, rotary joints, FRL units and pneumatic directional control valves.
