Limitations Of Pneumatic Actuators Single Acting Cylinders & Double Acting Cylinders

AIM: In this practical, we will study and note the limitations of single-acting and double-acting pneumatic cylinders used widely in pneumatic systems and industries.

 

OBJECTIVE: In this experiment, we will try to understand the basic construction of single-acting and double-acting cylinders and their working. Then, we will try to understand their limitations in pneumatic systems. Lastly, we will do a small comparison of single-acting and double-acting cylinders.

Single Acting Cylinders:

 BASIC UNDERSTANDING:

- A single-acting cylinder is a pneumatic actuator used in pneumatic systems.

- There are two ports in this type of cylinder: port “P” and port “E”.

- Compressed air is applied at port “P”, and port “E” is used as the exhaust.

-When pressure is applied at port “P”, the moving arm extends, and when the pressure is released, the moving arm retracts because of the spring mechanism.

- We can control the speed of this extension and retraction by using a pressure control valve.

LIMITATIONS:

-  Force Direction: Force is generated only in one direction; in the return direction, the force is dependent on the tension and size of the spring.

-  Spring Wear & Tear: In long-term and continuous operation, the spring becomes weak and reduces its performance.

-  Slow Retraction Under Load: The spring may be unable to retract the cylinder if a heavy load is attached to the moving arm.

-  Vibrations: The spring can cause vibrations when performing the retraction motion in the cylinder.

- Temperature Sensitivity: Extreme temperatures can affect spring performance.

- Higher Maintenance Need: The spring will need regular periodic maintenance.

APPLICATIONS IN THE INDUSTRIES:

- Single-Acting Cylinder is used in industries for the below applications:

- Clamping and holding lightweight materials.

- Ejection systems.

- Pushing lightweight materials.

- Automation with gravity return.

- Opening flaps.

- Lightweight carton positioning systems.

Double Acting Cylinders:

BASIC UNDERSTANDING:

A double-acting cylinder is also a pneumatic actuator used in pneumatic systems.

A double-acting cylinder has two ports; both can be used as pressure and exhaust one by one simultaneously.

When compressed air is applied to port P1, the cylinder will extend, and when compressed air is applied to port P2, the cylinder will retract.

When the cylinder is extending, port P2 is used as the exhaust, and when the cylinder is retracting, port P1 is used as the exhaust.

Motion in both directions in a double-acting cylinder is powered by compressed air.

LIMITATIONS:

Higher Air Consumption: A double-acting cylinder uses compressed air for both extending and retracting, increasing the operating cost.

More Complex System: Requires a separate 5/2 valve to operate the cylinder.

Higher Initial Cost: More components are used in this type of cylinder, so the initial setup cost is higher than that of a single-acting cylinder.

Air Leakage Risks Increase: More ports mean more seals and more piping, which ultimately increases the risk of leakages and breaks in the circuit.

Load Dependencies: How much load the cylinder can carry during extending and retracting movements depends on the air pressure and the speed of the cylinder.

APPLICATIONS IN THE INDUSTRIES:

Double-Acting Cylinder is used in industries for the below applications:

Heavy-duty clamping

Pick-and-place robots

Welding robots

Work piece positioning in CNC machines

3D printing industries

 

DESIGN IMPROVEMENTS WE CAN DO IN THE FUTURE:

Improved Sealing System: Use of low-friction, wear- and tear-resistant seals will reduce air leakages and improve efficiency and service life.

Cushioning at End Positions: Adding pneumatic cushioning at the stroke ends will reduce vibrations and noise in continuous operations.

Modular Design: Standardised mounts, ports, and accessories allow easy replacement in case of damage.

Inbuilt Pressure Control Valve: To control extension and retraction, a pressure control valve can be mounted directly on the cylinder’s body. It can also be modular.

 

COMPARISON TABLE:

Aspect	Single Acting Cylinder	Double Acting Cylinder
Air supply	Compressed air is applied to only one side of the piston.	Compressed air is applied to the both side of the piston.
Return mechanism	Spring mechanism is used to retract the piston.	Compressed air is used to retract the piston.
Ports	One air port.	Two air ports.
Output Force	Force available only on extension movement.	Force is available at both extension and retention movements.
Air Consumptions	Lower	Higher
Efficiency	Lower (Spring Control)	Higher
Load Handeling	Light loads	Medium to heavy loads
Construction	Simple	More complex
Cost	Cheaper	More expensive

 

CONCLUSION: 

By performing this experiment, we studied the two main types of cylinders used in pneumatic systems: the first is the single-acting cylinder, and the second is the double- acting cylinder. We also studied their basic construction and limitations based on industrial operations and applications. Lastly, we suggested some design improvements that we found during the operation of the cylinders.