Introduction
A machine’s actuator is the part in charge of moving and controlling a mechanism or system — for example, opening a valve. It is the “mover”: a device that receives a control signal and an energy supply, and converts that input into mechanical motion.
The control signal is typically low-energy (electrical voltage/current, pneumatic or hydraulic pressure, or even human input). The power source (electric, hydraulic, or pneumatic) is converted by the actuator into the required motion.
What is a Mechanical Actuator?
A mechanical actuator remotely controls or moves another mechanism using an external power source (electricity, compressed gas, or pressurised fluid). Common internal elements include lead screws, hydraulic pistons, and gear trains.
Output motion may be rotational or linear. Mechanical actuators are ideal for high-torque tasks (industrial or earth-moving equipment) and are widely used in manufacturing, agriculture, mining, and other industries where remote operation or safety is important.
Working Principle
Most mechanical actuators work by converting rotary motion into linear motion. This conversion is realized by structural components such as rails and gears, or chains and pulleys.
Design — Main Components
- Motor — primary source of power (commonly DC motors).
- Gearing — changes speed/torque between the motor and driven elements.
- Screw — converts rotation to linear displacement (lead or ball screw).
- Extension Tube — the moving rod/tube that extends or retracts with the nut/screw motion.
Some actuators include mechanical safety features such as a wrap-spring brake to hold a load if power is lost.
Types of Actuators
Pneumatic Actuators
Use compressed air or gas for movement. They are affordable, safe, and simple to operate, but require a compressor to maintain pressure.
Hydraulic Actuators
Use pressurised fluid to produce high power — common in heavy machinery. They deliver strong force but need skilled maintenance and can be sensitive to leaks and contamination.
Electric Actuators
Convert electrical energy into mechanical motion. They offer high precision and lower routine maintenance, but require continuous power and thermal oversight.
Advantages
- Easy to use and install
- High precision and reliable performance
- Customisable and adaptable to many applications
- Low maintenance and energy-efficient options
- Quiet operation with minimal leaks
Disadvantages
- Electric actuators can be less economical than pneumatic in some cases
- No inherent fail-safe position for many electric designs during power loss
- Pneumatic systems require a continuously running compressor
- Hydraulic systems need specialist maintenance and can leak
- Some types are sensitive to vibration and harsh environments
Applications
Mechanical actuators are used when controlled linear motion is required — elevation, translation, precise positioning, valve operation, cutting tools, material handling, and vibration/noise control systems.