A pneumatic cylinder is an actuator that uses compressed air to generate mechanical motion. It can convert the energy of compressed air into linear motion or force output, enabling a variety of mechanical actions such as pushing, pulling, clamping, and positioning, making it an essential component in modern industrial applications.

Understanding the components of a pneumatic cylinder is crucial for proper selection, installation, maintenance, and troubleshooting. While different types of cylinders may have variations in internal structure and operating methods, the core components are generally the same. Mastering the functions and characteristics of these components helps engineers and technician.

Common Components of a Pneumatic Cylinder

A pneumatic cylinder consists of multiple key components that work together to convert compressed air energy into mechanical motion, achieving linear reciprocating movement. The main structures are as follows:

Cylinder Tube / Barrel

The cylinder tube is the main body of the cylinder, designed to house the piston and maintain airtightness.

• Common materials: aluminum alloy, stainless steel, chrome-plated carbon steel, etc.

• The surface is usually treated with hard anodizing to improve wear resistance.

Piston

The piston moves back and forth inside the cylinder tube, converting air pressure into mechanical thrust.

• The outer circumference of the piston is equipped with seals to prevent air leakage.

Piston Rod

The piston rod connects the piston to external loads, transmitting the linear motion of the piston.

• The surface is usually hard-chrome plated or made of stainless steel to enhance strength and corrosion resistance.

Front Cover & Rear Cover

• The front cover guides the piston rod and holds the seals.

• The rear cover seals the other end of the cylinder and provides mounting points.

• Both end covers usually include air inlet/outlet ports.

Seals

Includes:

• Piston Seal

• Rod Seal

• Wiper Seal

• Static Seal (O-ring)

Function: maintain airtightness, prevent air leakage, and extend cylinder life.

Rod Guide / Bearing

Installed in the front end cover to support the piston rod, ensuring straight-line motion precision and reducing wobble and wear.

Mounting Parts

Includes:

• Cylinder base threads

• Flange

• Trunnion

• Foot bracket

• Mounting holes

Used to secure the cylinder to equipment.

Cushioning Mechanism

Cylinders with adjustable cushioning slow down at the end of the stroke to prevent impact.

• Typically includes an adjustable cushion needle valve.

Magnet

Used with magnetic switches (magnetic sensors) to detect the piston position.

• Usually embedded inside the piston.

Port

The air inlet or outlet at the front and rear of the cylinder (e.g., G1/8, G1/4, NPT).

• Used to connect the cylinder to air tubing or solenoid valves.

Piston Rod Thread and Rod-End Accessories

Includes:

• Male/Female threads

• Rod Eye

• Clevis Joint

• Ball Joint

Function: used to connect actuators or external loads.

Structural Differences of Different Cylinder Types

Single-Acting vs Double-Acting

• Double-acting: Both extension and retraction rely on air → air ports on both ends.

• Single-acting: One side powered by air, the other returns via a spring → only one air port, internal spring.

• Key difference: single-acting cylinders have a spring inside, double-acting do not.

Magnetic vs Non-Magnetic Cylinders

• Magnetic cylinders: piston embedded with a magnet.

• Used with magnetic switches to detect piston position.

• Key difference: magnetic cylinders have an internal magnet and a sensor slot on the cylinder body.

Standard (ISO, SC/SU) vs Compact Cylinders

• Compact cylinders have a shorter stroke and piston rod, with more integrated end covers.

• Cylinder body may be an aluminum extrusion rather than a round tube.

• Key difference: cylinder body structure (extruded vs conventional round tube).

Rodless Cylinders

This type has the greatest structural difference.

• Magnetic Coupling Type: transmits motion via magnets, no rod or rod guide.

• Mechanical Coupling Type (with slide): uses a slot and a slide to drive the load.

Key difference: no piston rod; instead, has a slide or mechanical transmission.

Rotary / Swing Cylinders vs Linear Cylinders

• Not linear motion; output is rotational.

• Structure includes:

• Vane or rack-and-pinion

• Rotor

• Output shaft

Key difference: motion type (rotational vs linear).

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