What is a Linear Actuator

 

What Is a Linear Actuator?

A linear actuator is a device that creates controlled motion in a straight line. Instead of rotating like a motor shaft, the output extends and retracts, pushes and pulls, or positions a load along one axis. If a drawer slides open, a hatch lifts, a TV rises from a cabinet, a valve stem moves in and out, or a solar panel changes angle, a linear actuator may be doing the work.

Actuators are often described as the muscles of machines because they convert an input energy source into useful motion. That energy may be electrical, hydraulic, pneumatic, or manual mechanical force. At FIRGELLI, the focus is electric linear actuators: compact motion devices that use a motor and mechanical drive system to turn electrical power into repeatable linear movement without pumps, compressors, or fluid plumbing.

Linear actuator showing straight line extension and retraction

In practical terms, a linear actuator is selected to do a job: move a load a specific distance, at a required speed, with enough force, within the available space, and under the expected environmental conditions. The best actuator is not simply the strongest one. It is the one that matches the geometry, duty cycle, control method, mounting arrangement, and safety margin of the application.

FIRGELLI C-Series Actuators, mini actuators, heavy-duty actuators, and control systems are used in applications such as smart furniture, machine access panels, robotics, marine hatches, agricultural equipment, ventilation systems, adjustable workstations, and automation projects. The common requirement is simple: dependable straight-line motion.

What’s Covered in This Guide

How Linear Actuators Work

A linear actuator is a system, not just a moving rod. In an electric linear actuator, the power supply energizes a motor. The motor rotates through a gear set, and that rotation turns a screw or similar drive mechanism. A nut or carriage travels along the screw, converting rotary motion into straight-line movement. The actuator housing keeps the mechanism aligned while the extension rod or output shaft transfers force to the load.

This conversion is why electric linear actuators are useful when the available power source is electrical but the required motion is linear. A DC motor naturally spins. The actuator’s internal gearing and screw mechanism translate that spin into controlled extension and retraction.

Linear actuator input energy and output motion diagram

For a deeper mechanical explanation of motors, gears, screws, and limit switches, see Linear Actuator Basics - How do Linear Actuators work?. If you are comparing body styles, read 6 Electric Linear Actuator Styles Explained.

The Main Parts of an Electric Linear Actuator

Power supply: Most small and medium electric actuators use low-voltage DC power, commonly 12V or 24V depending on the model. Existing Mini Linear Actuators are often used where space is limited, while larger designs may require a higher-current supply. Always confirm voltage, current draw, and wiring polarity before testing.

Motor and gear reduction: The motor provides rotational energy. Gear reduction trades motor speed for torque, which helps the actuator generate useful pushing or pulling force. In general, higher force actuators tend to move more slowly than lower force actuators using a similar motor envelope. This force-speed tradeoff is normal and should be considered early in the design.

Lead screw or drive screw: The screw is the mechanical converter. As it rotates, it moves the nut or extension mechanism linearly. Screw pitch, gear ratio, and motor speed all influence actuator travel speed, force, and resolution. For design work involving gear ratios and extension behavior, the Free Linear Actuator Gear Reduction Calculator can help estimate how mechanical choices affect output.

Extension rod, carriage, or moving output: This is the part connected to the load. Depending on the actuator style, the moving member may be a round rod, a track carriage, or another guided output. The connection must allow the actuator to move through its arc without side-loading the shaft.

Limit switches and feedback: Many electric actuators include internal limit switches to stop travel at full extension and full retraction. Some models also offer position feedback such as potentiometers, Hall sensors, or encoders. Feedback is useful when two actuators must move together, when a controller needs position information, or when repeatable intermediate stops are required.

Control device: A control can be as simple as a rocker switch or as advanced as a microcontroller, relay module, wireless remote, or FIRGELLI Control System. The control must be rated for the actuator voltage and current, and reversing polarity is typically how a DC actuator changes direction.

Electric, Hydraulic, Pneumatic, and Mechanical Actuators Compared

Different actuator technologies are useful in different situations. Electric linear actuators are usually preferred when the application needs clean installation, simple control, repeatable positioning, and low maintenance. Hydraulic systems are strong and compact for very high-force industrial tasks, but they require pumps, valves, hoses, and fluid management. Pneumatic systems are fast and simple where compressed air already exists, but precise positioning can be more difficult without additional controls.

Actuator type Energy source Best fit Engineering notes
Electric linear actuator DC or AC electrical power Automation, furniture, hatches, robotics, equipment adjustments Clean, easy to wire, good for controlled positioning; check force, speed, duty cycle, and environmental rating.
Hydraulic actuator Pressurized hydraulic fluid Very high-force equipment and heavy machinery Excellent force density; requires pump, reservoir, valves, hoses, and leak management.
Pneumatic actuator Compressed air Fast cycling in factories with existing air supply Simple and fast; air compressibility can make fine position control harder.
Mechanical/manual actuator Hand crank, lever, screw, or linkage Occasional adjustment where automation is not required Low electrical complexity; depends on operator input and may be slower.

How to Choose a Linear Actuator

Actuator selection is an engineering matching problem. The key variables are force, stroke length, speed, duty cycle, mounting geometry, control method, and environment. Start with the load and motion requirement, then work backward to the actuator.

1. Force: Determine the maximum force required to start and continue motion. A vertical lift is not the same as a hinged lid or sliding drawer. Hinges create changing leverage as the load rotates, so the actuator force may be much higher than the object weight suggests. Friction, binding, wind, snow load, and acceleration can also increase force. If the actuator is pushing on an inclined surface, review the Actuator Force Inclined Plane Calculation Guide + Calculator. For complex layouts, use Actuator Force Calculator as part of the sizing check.

2. Stroke length: Stroke is the distance the actuator extends. It is not the same as the length of the actuator body. Measure the required travel at the load connection point, not just the final movement of the object. For hinged applications, small changes in mounting location can greatly change the required stroke. See Linear Actuator Stroke Length: Calculate What You Need for a step-by-step approach.

3. Speed: Decide how fast the motion must happen under load. A hidden TV lift may need smooth, quiet motion rather than maximum speed. A vent opener may only need to move a few times per day. A production fixture may require a repeatable cycle time. To estimate extension time from stroke and speed, use the Free Actuator Speed Calculator.

4. Duty cycle: Duty cycle describes how long the actuator can run compared with how long it must rest. This matters because motors and gearboxes generate heat. A mechanism that moves once every hour is very different from one that cycles continuously. Learn the basics in What Is A Linear Actuator Duty Cycle And Why Does It Matter.

5. Static vs. dynamic load: Dynamic load is the force while the actuator is moving. Static load is the force it must hold when stopped. A hatch may be easy to move but still place a large holding load on the actuator when wind or vibration is present. The difference is explained in Linear Actuator Static vs Dynamic Load: Essential Guide.

6. Mounting and alignment: Mounting brackets must allow rotation as the actuator extends and retracts. A common mistake is to rigidly mount both ends so the actuator is forced to bend. Linear actuators are designed for axial push and pull loads, not side loads. If the actuator shaft visibly deflects during operation, the linkage or brackets should be redesigned.

Design question What to check Why it matters
How much force is required? Weight, leverage, friction, angle, wind, safety factor Undersizing causes stalls, overheating, slow movement, or premature wear.
How far must it move? Required travel at the actuator connection point Too little stroke prevents full motion; too much stroke can overdrive the mechanism.
How fast should it move? Extension time under expected load Speed affects user experience, cycle time, and available force.
How often will it cycle? Run time, rest time, cycles per hour Duty cycle limits protect the motor and gearbox from heat buildup.
Where will it operate? Indoor, outdoor, dust, moisture, temperature, vibration The environment influences housing style, sealing, wiring, and maintenance needs.
How will it be controlled? Switch, remote, relay, microcontroller, feedback controller The control system must handle current, direction reversal, position needs, and safety interlocks.

Practical Examples

Example 1: Hidden TV lift. Assume a builder needs to raise a TV vertically from a cabinet. The actuator stroke must at least match the required lift distance of the moving platform. The actuator force should cover the weight of the TV, lift frame, guide friction, and a safety margin. If the platform is guided by rails, the actuator mainly handles vertical force. If the actuator is mounted at an angle or drives a linkage, the force calculation changes. Smooth operation and quiet movement may matter more than high speed.

Example 2: Hinged hatch or trapdoor. A 50 lb hatch does not necessarily require only a 50 lb actuator. Near the closed position, the actuator may be pushing at a poor angle with limited leverage. The force requirement can be highest at the start of motion. The mounting points should be tested through the full range to confirm the actuator does not bottom out, overextend, or create side load. For this type of application, the Linear Actuator Mounting Position Calculator is especially useful.

Example 3: Adjustable vent or solar panel. The load may be moderate, but outdoor conditions matter. Wind can create momentary loads that are much higher than the panel weight. The actuator should be chosen with the environment, holding requirement, wiring protection, and duty cycle in mind. If position tracking is needed, feedback may be required rather than a simple two-wire actuator and switch.

Common Mistakes to Avoid

  • Choosing by weight only: Actuator force depends on geometry, leverage, friction, and motion angle, not just the object weight.
  • Ignoring side load: The actuator should push or pull in line with its shaft. Use pivots, brackets, or guides so the actuator is not forced to bend.
  • Confusing stroke with overall length: Stroke is travel distance. The actuator’s retracted and extended lengths must also fit inside the machine.
  • Forgetting duty cycle: An actuator that works in a short demo may overheat if cycled repeatedly without rest.
  • Undersizing the power supply: A supply must handle the actuator’s required current, including startup and loaded movement.
  • No end-of-travel plan: Confirm whether the actuator includes internal limit switches and whether the mechanism can safely stop at both ends.
  • No manual access or service plan: If the actuator is built into furniture, a hatch, or a vehicle, consider how it will be accessed if power is lost.

Quick Answer: What Is a Linear Actuator?

  • A linear actuator creates straight-line motion rather than rotary motion.
  • Electric linear actuators use a motor, gears, and a screw mechanism to extend and retract.
  • They are commonly used in home automation, robotics, hatches, furniture, machinery, and adjustable equipment.
  • Selection depends on force, stroke, speed, duty cycle, mounting geometry, control method, and environment.
  • Existing FIRGELLI product categories such as Heavy Duty Linear Actuators, Mini Linear Actuators, and Linear Actuators can be matched to different force, size, and control requirements.
FIRGELLI range of electric linear actuators

Linear Actuator FAQ

What does a linear actuator do?

A linear actuator moves something in a straight line. Depending on how it is mounted, it can push, pull, lift, slide, tilt, open, close, raise, or lower a load.

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

A motor produces rotary motion at its shaft. A linear actuator usually contains a motor plus gearing and a screw or drive system that converts that rotation into linear extension and retraction.

Can a linear actuator hold a load when power is off?

Many screw-driven electric actuators can hold position to some degree when stopped, but the correct answer depends on the actuator design, load direction, vibration, and static load rating. Always check the model’s rated static load and consider mechanical locks or supports where safety is critical.

How do I know what stroke length I need?

Measure the required movement at the actuator attachment point through the full mechanism travel. For a sliding application, this may be close to the desired object travel. For a hinged lid, the actuator stroke depends heavily on bracket locations and pivot geometry.

Can I run two linear actuators together?

Yes, but two standard actuators may not move at exactly the same speed under load. If synchronized movement is required, use a suitable controller and actuators with feedback, or design the mechanism so slight speed differences do not cause binding.

What is the most important sizing factor?

Force is usually the first critical check, but it is not the only one. A reliable selection also confirms stroke, speed, duty cycle, voltage, current draw, mounting alignment, environmental exposure, and control requirements.