How to use and control pneumatic systems

• Pneumatic systems use compressed air to create movement and force, and they are applied in various fields such as automated machinery, robotics, packaging, and construction.
• A single acting cylinder (SAC) is a pneumatic actuator that produces force and movement in one direction only, with a spring returning the piston to its original position.
• 3/2 valves are directional control valves with three ports and two positions, used to manage the flow of compressed air in pneumatic systems, crucial for controlling actuators like cylinders.
• Actuators in pneumatic circuits can be operated by different methods, including roller trip, push button, plunger, and lever, with the choice depending on the application.
• Logic circuits in pneumatics, such as AND and OR circuits, are created by ing valves together to control the operation of single acting cylinders, often used for safety and operational flexibility.
• Safety in pneumatic systems is paramount, requiring attention to high-pressure air, sudden movements, leaks, secure connections, and the use of personal protective equipment (PPE).

Pneumatic systems can be described using the input-process-output model:

• Input: the input is the compressed air that is supplied to the system.
• Control/process: the process is the way in which the compressed air is used to create movement and force. This can be done using various components, such as cylinders and valves.
• Output: the output is the movement or force that is produced by the system.

Pneumatic control systems are used in various applications, including:

• Automated machinery: pneumatic systems are used to control the movement of parts in automated machinery.
• Robotics: pneumatic systems are used to power the movement of robots.
• Packaging: pneumatic systems are used to operate packaging machinery.
• Construction: pneumatic systems are used to power tools such as jackhammers and nail guns.

A single acting cylinder (SAC) is a type of pneumatic actuator that produces force and movement in one direction only. It has a single port for compressed air to enter, which causes the piston to extend. The piston is returned to its original position by a spring.

A pneumatic single acting cylinder operates with an outstroke and an instroke.

During the outstroke, compressed air enters the cylinder through a single port, pushing the piston rod outward to perform tasks like pushing or lifting objects.

The instroke occurs when the air pressure is released, and a spring inside the cylinder retracts the piston rod back to its original position, readying it for the next cycle.

This type of cylinder is commonly used in applications requiring a single directional force, such as clamping mechanisms or ejecting parts.

3/2 valves or 3 port valves are directional control valves that manage the flow of compressed air in pneumatic systems. They work like a switch. They are crucial for controlling actuators like cylinders, enabling various automated operations.

Understanding 3/2 Valves

• 3 ports: 3/2 valves have three ports: one for the pressure source (air), one for the actuator (switch), and one for exhaust (to release the air).
• 2 positions: They have two positions, typically labelled as "open" and "closed," which determine the path of airflow.

In a pneumatic circuit, a 3/2 valve directs compressed air to extend or retract a cylinder. When the valve is in the actuated position, air flows to the cylinder, causing it to extend/outstroke. When the valve switches to the unactuated position, the air path to the cylinder is blocked, and the exhaust port opens, allowing the cylinder to retract/instroke (either by spring force in a SAC or with air pressure, depending on the cylinder type).

An actuator acts like a switch in a pneumatic circuit – it allows you to turn the circuit on and off. Valves can be actuated using different methods.

• Roller trip: actuated by a roller lever ing the valve.
• Push button: operated by pressing a button.
• Plunger: actuated by pushing a plunger.
• Lever: operated by moving a lever.

Selecting an appropriate actuator

Choosing the right actuator depends on the application and how the valve needs to be controlled. For example, a push button might be suitable for manual control, while a roller trip could be used for automated control based on the position of a machine component.

Logic circuits are made through ing valves together. The simplest type of logic circuit is an AND circuit.

One use for an AND logic of 2 valves in series is in situations where safety is important. For example, you can’t turn a saw on until you have pressed both buttons – this means you can’t accidentally turn it on.

An OR circuit is used to allow a machine to be turned off from different positions. This can also be a safety feature as other people can turn the machine off in an emergency.

OR circuits will always contain a shuttle valve. A shuttle valve allows air to be routed from either valve A or valve B depending on which one has been actuated.

• Unidirectional flow regulators, also known as one-way flow control valves (FCV), control the speed of cylinders in pneumatic circuits by restricting airflow in one direction.

• They contain an adjustable screw to vary the airflow restriction, limiting the cylinders' outstroke or instroke speed.
• To incorporate speed control, a unidirectional flow regulator is installed between the 3/2 valve and the SAC. By adjusting the needle valve, precise control over the SAC’s speed can be achieved, optimizing pneumatic operations for various tasks.

A unidirectional flow control valve placed between a SAC and a 3/2 valve with push button actuator. The compressed air is restricted on the outstroke of the SAC.

Pneumatic kits and boards offer a practical approach to understanding and building pneumatic systems. These kits typically include a base board for mounting components like cylinders and valves, which are connected using tubing. The process involves assembling these components according to a circuit diagram, providing a hands-on learning experience.

When constructing pneumatic circuits, it's crucial to use the correct pneumatic symbols to represent the different components. These symbols are standardised, ensuring clear communication and understanding of the circuit's function. Some common symbols include those for cylinders, valves, air preparation equipment, and flow control valves. Using these symbols correctly is essential for anyone working with pneumatics.

When working with pneumatic control systems, it is crucial to be mindful of potential hazards and adhere to safety practices during the design and construction phases.

Key Safety Concerns:

• High-pressure air: compressed air poses a significant risk of injury if mishandled. Always use proper safety equipment and follow established procedures.
• Sudden movement: pneumatic components can move unexpectedly and rapidly. It is important to keep hands and other body parts clear of moving components.
• Leaks: system leaks can lead to component failure and hazardous situations. Regular inspections and prompt repairs are essential.
• Connections: ensure that all connections are secure before switching on the compressed air.
• PPE: ensure that eyes are protected when constructing pneumatic circuits.