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Pneumatics · beginner

Double-Acting Pneumatic Cylinder

A linear air-powered actuator. Compressed air pushes a piston to extend or retract a rod that moves part of a machine.

Why it exists

Create simple, fast linear motion for clamping, lifting, pushing, sorting, and positioning.

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Double-acting pneumatic cylinder with piston rod, two ports and reed switch

Quick answer

What is a double-acting pneumatic cylinder?

A double-acting pneumatic cylinder turns air pressure into straight-line motion. A directional valve sends pressure to one side of the piston while the opposite chamber exhausts; reversing the valve reverses the force and rod direction. End sensors report retracted and extended positions back to the PLC.

Inside the control system

How the PLC relates to it

The PLC should command the valve and wait for the appropriate end sensor rather than assuming motion completes after a fixed delay. A robust sequence prevents extend and retract commands from conflicting, starts a travel timeout, and stops or recovers deliberately if the expected limit never arrives. Reed switches prove position only where they are mounted; they do not measure force, speed or whether tooling safely completed its work. For vertical loads, loss of air and stored-energy behaviour need explicit engineering controls.

Cause and effect

How it works, step by step

  1. 01

    The valve supplies air to one side of the piston.

  2. 02

    Pressure acting over piston area creates linear force.

  3. 03

    Air on the opposite side exhausts through the valve.

  4. 04

    End switches confirm that the cylinder really reached its commanded position.

01 / Open the case

Watch the mechanism do the work

Follow one highlighted causal link at a time, then operate the component and deliberately create the fault.

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Know the terminals

  • Cap-end air port
  • Rod-end air port
  • Extend reed switch
  • Retract reed switch

Recognize the faults

  • Air leak or low pressure
  • Flow control fitted in wrong direction
  • Side load damages seals
  • Command changes without end-position proof

Read the field guide

Go deeper on sizing, wiring conventions, test procedure, and the mistakes that damage equipment.

Open the complete guide

02 / Ask in context

Ask about this exact component

The Pro AI tutor receives this component’s mechanism, terminals, and common faults so its explanation stays grounded in the lab.

Selection checks

  • Required force from pressure and effective piston area, including losses and safety margin.
  • Stroke, mounting style, side-load capacity and available space.
  • Speed, cushioning and flow-control arrangement.
  • Magnetic piston and sensor type for end-position feedback.
  • Behaviour on loss of air, trapped pressure and vertical-load risk.

Commissioning sequence

  1. 1Confirm cylinder bore, stroke, mounting and load direction before applying air.
  2. 2Connect cap-end and rod-end ports to the correct valve outlets and set conservative flow control.
  3. 3Jog extend and retract while observing the mechanical travel and both end sensors.
  4. 4Adjust sensor positions so each indication changes reliably at the true end of stroke.
  5. 5Measure travel time under load, set a reasonable PLC timeout and test jam or low-pressure detection.

Troubleshooting answers

Frequently asked questions

Why use two end sensors on a cylinder?

They give independent proof of the retracted and extended states, allowing the PLC to sequence safely and diagnose a command that did not complete.

Should cylinder speed be controlled by restricting supply or exhaust?

Many pneumatic applications use meter-out control, restricting exhaust to improve stability. The correct arrangement depends on the load, valve and cylinder, so follow the pneumatic design guidance.

How should PLC logic handle a cylinder jam?

Start a timeout when motion is commanded, stop dependent actions if the expected limit does not arrive, remove or place outputs in the defined safe state, and require a deliberate recovery after the cause is addressed.

Now use it in a machine

Recognition is not mastery. Build the control logic, operate the process, and prove the fault response.

Program the full pneumatic motion

Free first success

Now control a double-acting pneumatic cylinder in a working machine

Move from recognition to PLC logic, feedback checks and fault recovery. The related guided exercise runs in your browser.

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Competency and practice field guide

Pneumatic-cylinder learning lesson: practice plan

Direct answer

The learner can predict extend and retract states, prove position separately from command and isolate air, valve, actuator, sensor or sequence problems.

Written for automation students learning how directional valves, air paths, cylinder mechanics, flow controls and end sensors form one PLC-controlled action.

an instructor and maintenance learner tracing a guarded safety and actuator signal path in an isolated diagnostic cell while studying pneumatic cylinder behavior, sequencing and fault evidence
System map / 02

NODE 01observable

Scope

Load, force, stroke, speed, pressure, cylinder type, valve state, ports, meter-in or meter-out flow control, cushions, end sensors and safe exhaust.

NODE 02observable

Signal path

PLC output through interface and directional valve to air path, cylinder motion, physical position, sensor feedback and sequence transition.

NODE 03observable

Baseline practice

Extend, prove, dwell, retract and prove repeated at a declared load and initial position.

NODE 04observable

Edge cases

Low supply, blocked exhaust, leak, sticky valve, reversed flow control, stalled rod, missing sensor, lost command and restart.

NODE 05observable

Fault practice

An energy, supply, valve, tubing, flow, cylinder, mechanics, sensor, output or sequence mismatch.

NODE 06observable

Transfer to the job

The training model redrawn and tested on safeguarded equipment using current component data.

Answer surface / 07

How does a double-acting pneumatic cylinder work?

A directional valve alternately supplies and exhausts the two cylinder chambers so pressure creates extension or retraction force.

Does a PLC output prove a cylinder moved?

No. It proves a command at one boundary; separate end-position or process feedback is needed to prove motion and completion.

Real double acting pneumatic cylinder footage

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Double-Acting Pneumatic Cylinder — Airflow, Force and Position