What is a linear actuator – Learn how electric motors work

What Is a Linear Actuator?

A linear actuator is a device that converts energy into straight-line motion — as opposed to the rotational motion produced by a standard motor. In simple terms, it pushes or pulls an object in a straight line. Linear actuators are used wherever precise, controlled linear movement is needed: raising a hospital bed, extending a solar panel, opening an industrial valve, or moving a machine arm along an assembly line.

Among all types, the linear electric actuator is the most widely adopted in modern industry due to its clean operation, programmable control, and low maintenance requirements. It uses an electric motor combined with a mechanical lead screw or ball screw to convert rotational energy into linear displacement.

How Does an Electric Motor Power a Linear Actuator?

Understanding how an electric motor works is key to understanding how a linear electric actuator operates. Here is the step-by-step process:

1. The electric motor receives current and generates rotational torque via electromagnetic interaction between the stator and rotor.
2. A gearbox or drive mechanism reduces speed and increases torque output to a usable level.
3. The rotational motion is transferred to a lead screw or ball screw assembly.
4. As the screw turns, a nut threaded onto it translates the rotation into linear motion, driving the output rod forward or backward.
5. Limit switches or encoders detect the end positions and signal the controller to stop or reverse motion.

The result is precise, repeatable straight-line movement that can be controlled electronically with millimeter-level accuracy.

DC Motor vs. AC Motor in Linear Actuators

Two primary motor types are used in linear electric actuators:

Most portable and mid-range industrial linear actuators use 24V DC motors, which offer a good balance of power, controllability, and compatibility with PLC-based systems.

Key Components Inside a Linear Electric Actuator

A typical linear electric actuator includes the following core components:

• Electric motor — provides rotational power (DC or AC)
• Gearbox — steps down speed and amplifies torque
• Lead screw or ball screw — converts rotation to linear thrust
• Drive nut — engages with the screw thread to produce axial movement
• Output rod / extension tube — the visible moving part that delivers force
• Limit switches — stop motion at fully extended or fully retracted positions
• Housing / enclosure — protects internals; rated by IP class (e.g., IP54, IP66, IP69K)
• Feedback sensor (optional) — encoder or potentiometer for position feedback

The quality of the screw mechanism strongly influences performance. Ball screws offer higher efficiency (up to 90%) and smoother motion, while lead screws are self-locking and more cost-effective for lower-duty applications.

Main Types of Linear Actuators Compared

Linear actuators come in several forms. Each has distinct advantages depending on the application environment:

Electric linear actuators are increasingly preferred because they require no hydraulic fluid, no air compressor, and generate zero leakage risk — making them ideal for clean environments and precision automation.

Core Performance Parameters You Need to Know

When selecting a linear electric actuator, these specifications define suitability for your application:

Stroke Length

This is the total distance the output rod travels from fully retracted to fully extended. Common ranges are 50 mm to 1,000 mm, with custom options available for special applications.

Load Capacity (Thrust Force)

Measured in Newtons (N) or kilogram-force (kgf). A small desk-height adjustment actuator may handle 200–500 N, while heavy-duty industrial models can exceed 20,000 N. Always factor in both static holding load and dynamic operating load.

Speed

Extension and retraction speeds typically range from 2 mm/s to 100 mm/s. Higher speed usually means lower force output given the same motor power — a trade-off managed through gearing ratio selection.

Duty Cycle

Expressed as a percentage (e.g., 25%, 50%, or continuous). A 25% duty cycle means the actuator can operate for 1 minute out of every 4 minutes. Exceeding duty cycle ratings leads to motor overheating and premature failure.

IP Rating

The Ingress Protection rating indicates resistance to dust and moisture. IP65 is standard for most industrial outdoor use; IP67 or IP69K is required for washdown or submersion environments.

Where Linear Electric Actuators Are Used

Linear electric actuators are found across a wide range of industries. Common real-world examples include:

• Agriculture: Automated seed gate control, greenhouse vent opening, tractor implement adjustment
• Medical & rehabilitation: Hospital bed elevation, patient lift tables, adjustable exam chairs
• Solar energy: Single-axis and dual-axis solar panel tracking to follow the sun throughout the day
• Industrial automation: Valve actuation, conveyor positioning, robotic arm linear joints
• Transportation: Truck tailgate control, bus door operation, seat adjustment in commercial vehicles
• Smart buildings: Automated window openers, skylight control, height-adjustable desks

In solar tracking alone, studies show that a single-axis tracking system using linear actuators can increase energy yield by 25–35% compared to fixed-tilt installations.

How to Size and Select the Right Linear Actuator

Choosing the correct actuator prevents costly failures and premature replacements. Follow this practical selection process:

1. Define the load: Calculate the total force required including static load, friction, and any safety margin (typically ×1.25 to ×1.5).
2. Determine stroke: Measure the exact travel distance needed from mount-to-mount geometry.
3. Set speed requirements: Decide how fast the motion needs to complete and whether variable speed control is needed.
4. Check duty cycle: Evaluate how frequently the actuator will operate per hour or per day.
5. Confirm environment: Select IP rating and material finish (e.g., anodized aluminum, stainless steel) based on exposure to water, chemicals, or dust.
6. Choose feedback type: Determine if position feedback (encoder, potentiometer) or limit-switch-only control is sufficient.

A well-matched actuator will operate well within its rated limits, extending service life to 10,000 cycles or more in typical applications.

Advantages of Electric Over Hydraulic and Pneumatic Actuators

The shift toward electric linear actuators in modern engineering is driven by clear, measurable benefits:

• No fluid leaks: Eliminates the contamination risk inherent to hydraulic systems
• Energy efficiency: Only draws power during movement; idle current is near zero
• Programmable precision: Position accuracy down to ±0.1 mm with encoder feedback
• Quiet operation: Noise levels typically below 55 dB in standard models
• Lower installation cost: No compressor, pump, or fluid reservoir needed
• PLC/IoT compatibility: Easily integrated with digital control systems and remote monitoring

FAQ: Linear Actuator and Electric Motor Basics

What is the difference between a linear actuator and a motor?

A motor produces rotational motion. A linear actuator converts that rotation into straight-line movement using a screw mechanism. In an electric linear actuator, the motor is integrated inside the actuator housing.

Can a linear electric actuator hold its position without power?

Yes. Actuators with a lead screw (rather than a ball screw) are self-locking and hold position when power is off. Ball screw models require a brake or holding circuit to maintain position.

What voltage do most linear electric actuators use?

12V and 24V DC are the most common for industrial and mobile applications. 110V and 220V AC models are used for fixed industrial installations.

How long does a linear electric actuator last?

Typical service life ranges from 10,000 to 100,000 cycles depending on load, duty cycle, and environment. Proper sizing and IP-rated protection significantly extend lifespan.

What does IP66 mean on an actuator?

IP66 means the actuator is fully dust-tight (6) and protected against powerful water jets from any direction (6). It is suitable for outdoor and washdown environments.

Is a linear actuator the same as a servo?

No. A servo system uses a motor plus a closed-loop feedback controller to maintain precise position or speed. A linear actuator may or may not include feedback — those with encoders can function as part of a servo system, but a basic actuator with limit switches is open-loop.