The combination of solenoid valves, pneumatic cylinders, and programmable logic controllers constitutes a precise closed loop control system. It consists of four core components that perform distinct roles and collaborate to complete automation tasks.
Programmable Logic Controller: The brain of the system, responsible for issuing commands and logic judgment.
Solenoid Valve: The switch of the system, responsible for controlling air circuit on and off states.
Pneumatic Cylinder: The muscle of the system, responsible for executing mechanical actions.
Sensor: The sensory organ of the system, responsible for feeding back action status.
Actuating Element: Pneumatic Cylinder
The pneumatic cylinder serves as the final executor of the system, converting compressed air energy into linear motion mechanical energy.
Double Acting Cylinder: The mainstream choice for industrial applications. It features two air ports, with both extension and retraction strokes driven by compressed air, delivering stable output force and controllable stroke.
Single Acting Cylinder: Has only one air port, using compressed air to drive one direction while relying on spring force for return. It features a simple structure but has limitations in output force and stroke.
Special Types: Rodless cylinders that save space and guided cylinders that resist lateral forces are designed to meet specific working condition requirements.
Control Element: Solenoid Valve
The solenoid valve acts as the bridge connecting electrical signals and the pneumatic system. It receives commands from the programmable logic controller and changes the flow direction of compressed air by switching the internal spool.
5/2 Way Valve: The standard configuration for controlling double acting cylinders. It has one pressure inlet, two cylinder outlet ports, and two exhaust ports, enabling cylinder reciprocating motion through power on and power off states.
3/2 Way Valve: Typically used for controlling single acting cylinders, featuring a simple structure with only one working outlet port.
Feedback Mechanism: Sensors
To enable the system to determine whether cylinder actions are complete, sensors must be introduced for position feedback, forming closed loop control.
Magnetic Switch: The most commonly used position sensor. It is mounted on the cylinder barrel, and when the piston moves to the designated position, the magnetic ring on the piston triggers the switch, sending an in position signal to the programmable logic controller.
Pressure Switch: As an advanced safeguard, it monitors air circuit pressure. Through dual confirmation of position and pressure, it ensures the cylinder not only reaches the position but also delivers the required output force, effectively preventing safety hazards such as insecure workpiece clamping.
Logic Center: Programmable Logic Controller
The programmable logic controller serves as the command center of the entire system, with its internal program responsible for processing all signals and logic.
Sequential Control: The program determines the next action based on sensor feedback signals. For example, it will only issue an extend command after receiving the retracted in position signal.
Interlock Protection: This is the core safety principle of program design. It ensures that the extend and retract control signals are never output simultaneously, thereby preventing solenoid valve coil burnout or air circuit conflicts, and safeguarding equipment and personnel safety.
