Guide to Choosing Industrial Cylinders Types and Uses

In the wave of industrial automation, pneumatic technology has secured a vital position due to its efficiency and cost-effectiveness. However, with numerous cylinder products available in the market, selecting the most suitable model for specific applications remains a challenge for many engineers and technicians.

Pneumatic cylinders, also known as pneumatic actuators, are mechanical devices that utilize compressed air to generate linear or rotary motion. The history of pneumatic technology dates back to the 1st century AD when Greek engineer Hero of Alexandria first explored pneumatic principles. Today, cylinders are widely used in industrial automation systems for various tasks including material handling, cutting, conveying, packaging, filling, and pressing.

These components serve as downstream actuators in pneumatic systems, driving complete operations as intended - earning them the nickname "muscles" of pneumatic systems. Their excellent performance, technical adaptability, and economical maintenance costs make them highly valued in industrial automation.

Based on design and motion capabilities, cylinders can be categorized into several main types:

• Linear cylinders: Generate straight-line motion in both horizontal and vertical directions
• Rotary cylinders: Produce rotational movement
• Swivel cylinders: Combine linear and rotary motion
• Rodless cylinders: Feature no piston rod extending from the cylinder body, achieving linear motion through magnetic or mechanical coupling

Among these, linear cylinders are the most common type, further divided into single-acting and double-acting cylinders based on their operation method and port configuration.

Linear cylinders, with their simple structure and reliable operation, provide precise straight-line motion in industrial applications.

Single-acting cylinders drive loads in one direction using compressed air, while returning via spring force or other external means. These cylinders feature only one air port for compressed air input and come in two variants based on the piston rod's initial position.

• Push-type cylinders: The piston rod remains retracted without air supply. When compressed air enters, the rod extends to push the load. After air release, an internal spring returns the rod to its initial position.
• Pull-type cylinders: The piston rod extends without air supply. When compressed air enters, the rod retracts to pull the load. The spring then returns the rod to its original position after air release.

Single-acting cylinders offer simple structure and lower cost but have limited stroke and provide power in only one direction. They're typically used for intermittent actions or single-direction applications like clamping and positioning.

Double-acting cylinders drive loads in both directions using compressed air, featuring two ports to control extension and retraction. Unlike single-acting models, they lack spring return mechanisms, with piston rod position entirely controlled by air pressure.

These cylinders operate by alternating compressed air supply between ports to achieve reciprocating motion. The effective volume difference between extension and retraction creates slightly different thrust forces, typically greater during extension.

Double-acting cylinders provide longer strokes, greater thrust, and bidirectional power, making them ideal for continuous reciprocating motion or dual-direction force applications like material handling and machining.

Cylinders convert compressed air energy into mechanical motion through piston movement driven by air pressure. The motion state typically involves either extension or retraction of the piston rod, with travel distance determined by cylinder design and size.

Single-acting cylinders use one air port to drive piston rod movement in one direction, with spring return when pressure decreases. Motion direction varies between push-type and pull-type models.

Two ports alternately control extension and retraction. The piston rod's space occupation creates different effective volumes during each stroke, resulting in varying thrust forces between movements.

Rotary cylinders generate rotational movement through more complex internal mechanisms like piston-rod-gear-rack systems that convert linear to rotary motion. Two main types exist:

• Single-rack rotary cylinders: Use one rack to drive gear rotation via piston movement and airflow direction control
• Double-rack rotary cylinders: Employ two synchronized racks for greater torque and precision

Note that rotary cylinders typically can't achieve continuous rotation, with angles usually limited to 180° (model-dependent). Continuous rotation applications generally require electric actuators.

The cylinder body houses internal components with end covers (front and rear) that may feature one or two air ports for hose connections. Compressed air enters through these ports to drive piston movement and energy conversion.

This movable internal part divides the barrel into two chambers, driving the piston rod's movement based on air entry direction. Forward motion occurs when air enters the rear port, with corresponding chambers labeled "+" and "-".

Connected directly to the piston, the rod's end typically attaches to mechanical components needing movement. Stroke length refers to the maximum travel distance determined by cylinder size and design.

This mechanism reduces impact during retraction, lowering shock, vibration, and noise to enhance motion stability and speed.

Critical for preventing air leakage between chambers, these seals maintain pressure by keeping air in designated areas.

Made from chemical-resistant, low-friction plastics like PTFE or polyamide, these rings minimize wear by preventing direct piston-barrel contact.

Modern pneumatic actuators often incorporate sensors like magnetic proximity or Hall-effect types to precisely detect piston position during movement.

These steel rods (typically four or more) connect end covers, securing components and providing external impact protection.

Choosing the right cylinder involves considering several key factors:

• Load: Determine the weight needing movement and select adequate thrust capacity
• Stroke: Identify required travel distance
• Speed: Specify necessary motion velocity
• Environment: Consider temperature, humidity, and corrosive elements when selecting appropriate protection levels
• Mounting: Choose suitable installation methods (flange, foot, trunnion, etc.)
• Control: Select compatible control methods (direct, solenoid valve, proportional valve)

Additional considerations include cost, lifespan, and maintenance requirements for optimal model selection.

This guide has thoroughly examined pneumatic cylinder principles, types, and components to facilitate informed selection for industrial applications. Understanding different cylinder characteristics enables better choices that enhance productivity while reducing maintenance costs. Comprehensive evaluation of load, stroke, speed, environment, mounting, and control factors ensures safe, reliable operation.