Operating a Double-Acting Pneumatic Cylinder with START and STOP Push Buttons (Close Priority)
Introduction
A double-acting pneumatic cylinder operates using compressed air for both extension and retraction. In this setup, we use START and STOP push buttons to control the movement of the cylinder, with a close priority system. This means that if both buttons are pressed simultaneously, the STOP button takes precedence, ensuring the cylinder retracts for safety and control.
This article covers the working principle, components, pneumatic circuit design, and AutoSIM 200 simulation of this system.
Working Principle
- START Push Button (NO - Normally Open): Activates the cylinder extension when pressed.
- STOP Push Button (NC - Normally Closed): Deactivates extension and forces retraction when pressed.
- Close Priority Logic: The STOP button overrides the START button, ensuring the cylinder retracts when both buttons are pressed at the same time.
Applications
Safety-critical automation processes
Emergency stop mechanisms
Industrial assembly and material handling
Pressing and clamping operations
Components Required
- Double-Acting Cylinder – Performs bidirectional movement.
- 5/2-Way Double Pilot Valve – Controls air supply for extension and retraction.
- START Push Button (3/2-Way NO Valve) – Sends air to the extension side.
- STOP Push Button (3/2-Way NC Valve) – Sends air to the retraction side.
- Air Compressor – Provides compressed air.
- Flow Control Valves (Optional) – Controls the speed of movement.
- Air Tubing and Fittings – Connects the components.
Pneumatic Circuit Design
Step 1: Understanding the Valve Function
START PB (NO - Normally Open, 3/2-Way Valve)
- When pressed → Air flows to pilot side A of the 5/2-way valve, extending the cylinder.
- When released → The cylinder remains extended due to the pilot signal holding the valve in position.
STOP PB (NC - Normally Closed, 3/2-Way Valve)
- When pressed → Sends air to pilot side B of the 5/2-way valve, retracting the cylinder.
- When released → The cylinder remains retracted, overriding the START command.
Step 2: Circuit Working Mechanism
Press START Button:
- The 3/2-way NO valve opens.
- Air enters the pilot port A of the 5/2-way valve.
- The cylinder extends.
Press STOP Button:
- The 3/2-way NC valve opens.
- Air enters the pilot port B of the 5/2-way valve.
- The cylinder retracts.
- Since STOP has priority, the cylinder remains retracted even if START is pressed.
Implementation in AutoSIM 200
To simulate this circuit in AutoSIM 200, follow these steps:
- Open AutoSIM 200 and create a new project.
- Add components from the pneumatic library:
- Double-acting cylinder
- 5/2-way double pilot valve
- 3/2-way NO valve (START PB)
- 3/2-way NC valve (STOP PB)
- Air supply
- Connect the components using air tubing.
- Run the simulation and observe the following:
- Press START PB → Cylinder extends.
- Press STOP PB → Cylinder retracts.
- If both buttons are pressed, the STOP PB takes priority.
Conclusion
Using a double-acting pneumatic cylinder with START and STOP push buttons ensures controlled movement, with the STOP button having priority for safety. This setup is commonly used in industrial automation, machine safety systems, and material handling applications.
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