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Comprehensive Guide: Understanding Pneumatic Cylinder Types

Preface

This is our detailed guide on pneumatic cylinders, and we are excited to share it with you. This guide is created to improve your knowledge of pneumatic cylinders and their importance in many industries, whether you are an experienced engineer or a newbie in the field of automation. Through the reading of this guide, you will understand not only the basic but also the intricate aspects of pneumatic cylinders, thus you will be able to make the right decisions in your projects and applications.

What is a Pneumatic Cylinder ?

Pneumatic Cylinder Types (4)

A pneumatic cylinder is a device that is created to transform the energy from the compressed air into the linear motion. Unlike the hydraulic cylinders, which are based on the hydraulic oil, pneumatic cylinders are the best for applications where cleanliness and safety are the most important factors because they use air pressure. The simplicity of these robots is the reason why there is less leakage and contamination, so they can be used in various industries such as manufacturing, packaging, and automation.

The pneumatic cylinder is composed of a cylinder body, which is usually made of stainless steel or aluminum, and a piston that moves back and forth along the cylinder. The piston diameter and the bore size are the main factors as they are the ones that determine the force the cylinder can exert. The air pressure applies on the piston rod, which either extends or retracts in a straight line, thus, the positioning and motion control of the object become very precise. The cylinders have features like adjustable cushioning that slow down the piston at the ends of the stroke to avoid the impact and the noise.

What is a Pneumatic System?

It is a system that uses compressed air to transmit and control energy. A pneumatic system efficiently uses the power of compressed air to do mechanical work by the means of a series of components that are interconnected. In the center of the system is a compressor that transforms mechanical energy into pneumatic energy by compressing air. This compressed air is then passed through the air treatment units which usually include filters to remove the impurities, regulators to control the pressure, and lubricators to reduce the component wear. The conditioned air is then passed through a system of pipes and fittings that direct its flow and direction to different valves that regulate its flow and direction. Lastly, the compressed air reaches the actuators like pneumatic cylinders, where its energy is turned into mechanical force to accomplish the tasks that are needed.

Advantages of Pneumatic Systems

The pneumatic system design is simple, and the components of the system are mainly cylinders, valves and pipes, which makes them easy to install and maintain. The less complex parts that can malfunction or break, the simpler this design is and the reliability of it increases, thus the downtime reduces and the productivity increases . Besides, pneumatic systems have the reputation of being reliable and lasting for a long time. Compressed air is the main source of energy in this case and this implies that components are not subject to the same level of wear as components in hydraulic or electrical systems. These factors, together with the simplicity of maintenance, make pneumatic systems a cheap automation solution in the long run.

ISO Standards and Form Factors of Pneumatic Cylinder

Pneumatic Cylinder Types (3)

ISO Standards

ISO standards for pneumatic cylinders are the worldwide rules that describe the design, performance and testing of these parts. The main goal of these standards is to make sure that the products from different manufacturers are consistent, compatible, and safe to use. Here are some of the key ISO standards related to pneumatic cylinders.

ISO 6432: This standard includes the single rod, double-acting cylinders with bore sizes from 8 to 25 mm. It is the one that specifies the dimensions, tolerances, and performance characteristics for these compact cylinders.

ISO 15552 (previously ISO 6431): This standard covers the single rod, double-acting cylinders with bore sizes from 32 to 320 mm. It specifies the dimensions, tolerances, and the performance requirements for these larger cylinders that are mostly used in industrial applications.

ISO 21287: This standard is about the single rod, compact cylinders with the bore sizes from 20 to 100 mm. It is about the dimensions, tolerances, and performance specifications for these space-saving cylinders.

ISO 15524: The standard is about rodless cylinders, which are the ones that have a sliding carriage instead of an extending rod. It gives the dimensions, tolerances, and performance characteristics of these cylinders that are usually used in the applications where space is a problem.

ISO 4393: This standard covers single rod, double-acting cylinders with detachable mountings. It sets the dimensions and tolerances for the mounting interfaces, thus the cylinders and the mounting accessories from different manufacturers will be compatible.

ISO 10099: This standard deals with pneumatic cylinders with magnetic pistons that can be used for non-contact position sensing. It lays down the dimensions and the performance standards for these cylinders and their accompanying magnetic sensors.

These ISO standards are about pneumatic cylinder design and they cover many aspects of it like the bore and rod diameters, stroke lengths, mounting dimensions and thread sizes, piston and rod seals, port sizes and locations, cushioning requirements, performance characteristics like the maximum operating pressure, force output, and air consumption.

Form Factors

The form factors of pneumatic cylinders are the mounting options which include flange, foot, clevis, and trunnion mounts, thus, the cylinders can be easily applied and installed in different places.

Flange Mounting: This way, the cylinder is firmly attached to the machine structure by the end caps or heads that are directly connected to the cylinder. Flange mounts are perfect for applications that need high stability and the least movement at the mounting points. Flange mounts help to distribute the load evenly, thus reducing the stress and the wear of the cylinder. The so-called mounting style is especially useful when the exact positioning is a must and it is mostly used in industrial automation and material handling systems.

Clevis Mounting: The pivot point at the end of the cylinder is the clevis mounting that is used for the applications where the cylinder must move in an arc. This type of mount is suitable for the applications where the cylinder must swing which is the main component of the robotic arms or gate operations where the angular movement is necessary. It is of great help in keeping the alignment and reducing the side loads that can be the cause of premature wear out of the cylinder.

Foot Mounting: Foot mounts are the best option if you need to install the cylinders vertically or horizontally. They are used for providing a solid foundation and support. This kind is specially designed for cases where the cylinder has to be either standing upright or lying horizontally, thus it is the best in such situations to ensure stability and alignment. Foot mounts are commonly found in presses or lifting applications where the cylinder exerts force in a straight line against gravity.

Trunnion Mounting: The cylinder is allowed to pivot around the axis of the trunnion pins, thus giving it a swinging motion that is very important in the applications that require the cylinder to follow a curved path. This kind of mount is perfect for machinery where the cylinder must be in line with the other moving parts that are not perfectly linear.

Types of Pneumatic Cylinders

Pneumatic Cylinder Types (2)

There are some common types of pneumatic cylinders.

Single-acting Cylinders

Features

Single-acting pneumatic cylinders work with compressed air pushing the piston in one direction and a spring returns it to the original position. The design of the cylinder reduces the cylinder structure and the air consumption because air is only used to move the piston in one direction, thus, it is more energy-efficient for some applications than the double-acting cylinder.

Advantages and Disadvantages

The main benefits of single-acting cylinders are their simplicity, low cost, and fewer components which make them easy to install and maintain, and their lighter and more compact design makes them perfect for applications with limited space or where only a single directional force is needed. Nevertheless, the dependence on a spring for the return stroke can be a drawback, as the force exerted by the spring is usually less than that of compressed air, thus limiting the amount that can be returned, and this spring mechanism can also influence the speed and the consistency of the return stroke, which in turn can affect the precision of the operations.

Applications

  • Manufacturing (e.g., clamping and holding, feeding mechanisms)
  • Automotive Industry (e.g., production line equipment, vehicle maintenance)
  • Consumer Products (e.g., home appliances and gadgets)

Double-acting Cylinders

Features

The double-acting pneumatic cylinders are the versatile devices that are used to control the motion in both the extending and retracting directions by means of the air pressure applied alternatively on both sides of the piston. The combination of two-way action makes it possible to have more precise control and a greater force application than the single-acting cylinders that only use air pressure on one side and usually rely on a spring for return action.

Advantages and Disadvantages

The main advantages of double-acting cylinders are that they can exert force in both directions, which increases the control and effectiveness in different applications, enables the movement of heavier loads, and allows the use in more complex sequences in automated systems, with the precise control over retraction speed and force that is very important for the synchronization and the precise positioning. Nevertheless, they have some drawbacks, like the need for a more complicated and costly arrangement due to the additional control valves and intricate piping that are used to control the air flow to both sides of the piston, and the fact that they consume more air than single-acting cylinders because the air is used for both extending and retracting the piston, which could lead to higher operational costs

Applications

  • Automotive Industry (e.g., automotive assembly, testing equipment)
  • Entertainment and Stagecraft (e.g., theatrical machinery)
  • Agriculture (e.g., harvesting equipment, automated feeding systems)

Rotary Cylinders

Features

Rotary cylinders, which are also called rotary actuators, turn compressed air into rotary motion and are famous for their compact and efficient design. These cylinders operate by means of a vane or rack and pinion system inside a sealed chamber; the compressed air pushes the vane or gear to rotate, thus, converting the linear force of the air into rotary motion. This mechanism is the one that makes it possible to have the exact angular positioning, which is a major plus in the fields where the rotational movement is needed.

Advantages and Disadvantages

The main advantage of rotary cylinders is their high torque in a small form, which is why they are perfect for applications that are limited in space. Besides, they also provide a good control over the rotation, which can be easily adjusted according to the desired angle of movement. Nevertheless, their negative aspects are the limited range of rotation—usually less than 360 degrees—and, and the possibility of wear in the vane or gear system, which can affect performance over time.

Applications

  • Manufacturing Sector (e.g., assembly robots, rotating parts during machining)
  • Packaging Industries (e.g., rotary cylinders in capping machines)

Rodless Cylinders

Features

Rodless cylinders are a special type of pneumatic cylinder that have a distinct advantage in situations where space is limited. Unlike the conventional pneumatic cylinders that extend a rod outside the cylinder body, the rodless cylinders have the piston inside a sealed tube, with the piston coupled to an external carriage. This design has the same stroke as the rod-type cylinders, but without extending beyond the cylinder length, thus, they are perfect for the compact spaces.

Advantages and Disadvantages

The main way of rodless cylinders is generally the magnetic or mechanical coupling system that connects the piston to the carriage that moves around the outside of the cylinder. This enables the straight movement without the rod sticking out, therefore, the profile is compact. Besides, the advantages of rodless cylinders consist in their compact design and the fact that they can carry the load directly on the carriage, which makes the mechanical system design much easier. Furthermore, they can also perform longer strokes than the traditional ones because they do not have the risk of rod buckling.

Nevertheless, rodless cylinders are usually more expensive than rod-type cylinders and might be more vulnerable to leakage because of the long, continuous seal that is needed along the cylinder. Moreover, the external guide for the moving carriage can complicate the process and increase the maintenance needs.

Applications

  • Manufacturing (e.g., screwing caps on bottles, machine tool changers )
  • Packaging Machinery (e.g., rotating goods for labeling, capping, or inspection)
  • Automotive Industry (e.g., engine and dashboard installations)

Telescoping Cylinders

Features

The telescoping cylinders, also called the multi-stage cylinders, are the ones that have a design of the piston rods that are nested inside each other and they extend sequentially. The peculiar structure of these cylinders enables them to have a much longer extension than their retracted length, thus they are perfect for the cases where the space constraints do not allow the use of the standard cylinders but a long stroke is needed.

Advantages and Disadvantages

Telescoping cylinders have the advantage of their long reach while keeping a compact retracted size, which is important in applications where the installation space is limited. Besides, they are capable of generating strong force, which is perfect for lifting heavy things. The disadvantages of this are that they are very complicated to design, which leads to higher costs and maintenance. They are also generally slower to extend and retract than the single-stage cylinders, and stability can decrease when fully extended, especially if the load is not evenly distributed.

Applications

  • Transportation (e.g., dump trucks and recycling truck)
  • Construction (e.g., forklifts and hydraulic lifts)
  • Agriculture (e.g., booms on sprayers or harvesters)
  • Emergency Services (e.g., ladder trucks, enabling ladders)

Compact Cylinders

Features

Compact cylinders are created to have the same functionality as standard pneumatic cylinders but in a smaller and more space-efficient form factor. These cylinders usually have a shorter stroke and a smaller diameter, which makes them the best for applications where space is limited.

Advantages and Disadvantages

Compact cylinders have the advantage of being very small so they can be installed in tight spaces without losing performance. They are light, which is good for cases where the weight of the machine is reduced. Moreover, they have quick response times because of the small amount of air needed to fill the cylinder, hence they are good for high-speed applications.

Cons of this type of cylinder are the fact that they usually have a lower force output than the standard cylinders because of their small piston diameter. Moreover, they might have a restricted stroke length that can be a problem in situations that need bigger movements. The compact design may also imply that they are not as strong under high mechanical loads.

Applications

  • Automation and Robotics (e.g., precise, controlled movements)
  • Consumer Electronics Manufacturing (e.g., smartphones and tablets)
  • Packaging Machinery (e.g., small-scale filling, sealing, labeling machines)

Guided Cylinders

Features

The cylinders that are guided by the rods, also called the slide or rod-guided cylinders, are made to give the exact and stable linear motion by using the guide rods that are parallel to the piston rod. These guide rods, which are helpers, make the load more stable and prevent rotational movements. Thus, the alignment is more accurate and the load-carrying capabilities are enhanced.

Advantages and Disadvantages

The guided cylinders have the various advantages. First, they enable the linear motion to be more precise, And they are more resistant to the side loads and torsional forces. This makes them appropriate for the use in cases where the precise positioning and handling of the heavier or uneven loads are needed, which could be a source of instability for the standard cylinders. Besides, guided cylinders usually have longer bearing surfaces, which hence decrease wear and hence increase the durability of the system.

The disadvantages may be the bigger footprint of the guided pneumatic cylinders in comparison with the standard ones, since the extra components for guiding need more installation space. The complexity and the cost of these cars can be higher because of the additional mechanical parts such as the guide rods and bearings.

Applications

Packaging Industry (e.g., filling, capping, and labeling)

Design Considerations of The Pneumatic Cylinder

Pneumatic Cylinder Types (5)

The design of the Pneumatic Cylinder is a set of elements that are included in the construction of the Pneumatic Cylinder.

Cylinder Type: Single-acting is suitable for applications that are simple and space-saving and need the force in one direction. Moreover, double-acting is the best for control and force for both the extending and the retracting, thus it is the best for strong applications.

Material: Stainless steels are mostly used for cylinder bodies and piston rods to avoid corrosion and ensure durability.

Bore Size: The factor that decides the force output is the one that is being referred to here. The bigger the bore, the bigger the force it can handle.

Stroke Length: The distance of the load that has to be moved should be the same as the distance of the tractor that is pulling it. The ideal length is the one that is not too long or too short, but it is enough to achieve the goal without wasting space.

Air Pressure: Must be compatible with system’s maximum operating pressure. The higher pressure can cope with the higher loads.

Adjustable Cushioning: The major role of the piston at the end of its stroke is to reduce the wear of the components by cushioning the piston.

Temperature: Seals and materials must be able to withstand operational temperatures.

Exposure: Rejection of chemicals or particulates if they are relevant.

Operational Environment: Environmental compatibility is a major issue which includes the problem of the use of special seals in cold or corrosive environments.

How to Choose the Right Cylinder?

Selection CriteriaKey Considerations
Cylinder TypeSingle-acting: Best for simple direction force applications.
Double-acting: Suitable for applications needing force in both directions.
Rodless: Saves space while providing the same stroke length.
Telescopic: Ideal for long stroke requirements in compact spaces.
Compact: Fits into small spaces without sacrificing power.
Material and ConstructionStainless steel cylinders: Preferred for harsh environments or cleanliness requirements.
Adjustable cushioning: Reduces impact at stroke ends, beneficial for high-speed operations.
Bore Size and Stroke LengthBore size: Larger for more force; match with the load requirement.
Stroke length: Match with the required movement distance; ensure it fits the installation space.
Operating Pressure and Air SupplyEnsure compatibility with the system’s available air pressure. Higher pressures are suitable for heavier duties.
Environmental FactorsTemperature: Choose cylinders with seals and lubricants that can withstand operational temperatures.
Exposure: Consider cylinders with protective coatings if they are to be used in corrosive or dusty environments.
Load and Speed RequirementsDetermine the necessary force and speed for cylinder operation. Select specifications that align with these operational demands to ensure efficiency and durability.

Conclusion

In the future, pneumatic cylinders will be all about the better accuracy, efficiency and adaptability. This new development will be based on smart technologies, for example, sensors and IoT connectivity, that will help in the prediction of maintenance needs and the improvement of operational efficiency. Moreover, as the field of materials science progresses, cylinders will be lighter and more robust, thus reducing the energy consumption in pneumatic systems and increase the lifespan of these systems. This new material and the new manufacturing technique will enhance cylinder performance and ecological sustainability. Besides, the progress in valve technology and air handling technology will be the main factor of the increase in the efficiency and reliability of pneumatic systems, so pneumatic systems will still be the most important part of modern industrial automation.

Common problems of Pneumatic Cylinders

Are pneumatic cylinders that can be tailored for particular uses available?

Yes, pneumatic cylinders can be adapted to the specific needs, which include the changes in stroke length, the bore size, the materials, and the mounting options. Custom seals, sensors, and even the specialized port positions can be added to the unique operational environments and functions to suit the needs of each user.

What is the bore size and how does it impact the performance of a pneumatic cylinder?

The bore size of a pneumatic cylinder is the determining factor of its force output; the larger the bore size, the more force can be generated because it has a larger area for the air pressure to act upon. Nonetheless, bigger bores need more compressed air to move, which in turn will affect the efficiency and the operational costs.

How are single-acting and double-acting pneumatic cylinders different from each other?

Single-acting cylinders work with air pressure to move the piston in one direction and a spring to return it, thus they are the best for the simpler tasks that require force in only one direction. Double-acting cylinders are the ones that use air pressure for both extension and retraction, thus providing more exact control and power for complex or heavy-duty operations.

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