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Linear Actuator Selection Guide: Complete Engineering Reference for Force, Stroke, Speed, and Control

This page is a permanent engineering reference for linear actuator selection, sizing, mounting, and control.

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Table of Contents

1. What a Linear Actuator Is

what an actuator iswhat an actuator is

A linear actuator is a mechanical device that converts energy into controlled straight-line motion. Unlike a rotary motor that produces continuous rotation, a linear actuator extends and retracts along a single axis to push, pull, lift, open, close, position, or clamp a load.

Most electric linear actuators are built from a motor and gear reduction driving a screw mechanism (lead screw or ball screw) that translates rotary motion into linear travel.

Exploded view of an electric linear actuator showing motor, gearbox, lead screw, and rod.
Figure 1. Detailed engineering diagram of a DC electric linear actuator's internal components. Illustrates how the DC motor drives the gear reduction and lead screw to extend and retract the rod. Key parts labeled: electric motor, planetary gearbox, lead screw nut, and limit switches..

Most modern electric linear actuators consist of:

  • An electric motor

  • A gear reduction stage

  • A lead screw or ball screw

  • A translating rod or carriage

  • A structural housing

  • End-of-stroke limit switches (internal or external)

Why linear actuators are used

Linear actuators are chosen when an application requires:

  • Predictable, repeatable motion

  • Compact packaging

  • Straight-line movement without linkages

  • Simple electrical control

  • High force at low speed

Where linear actuators are used: adjustable furniture (desks, beds), doors and hatches, RV and marine systems, robotics, industrial automation, positioning fixtures, and general motion control where predictable linear travel is required.

2. What a Linear Actuator Is Not

Many devices move in a straight line, but they are not interchangeable. Understanding category boundaries prevents incorrect design assumptions.

Chart comparing linear actuators vs gas struts vs hydraulic cylinders.

Figure 2. Technical comparison chart highlighting differences between powered linear actuators, passive gas struts, and hydraulic systems. Shows distinct force generation methods, control capabilities, and typical use cases for electric vs. fluid power.

Gas struts (gas springs)

Gas struts provide passive force assistance using compressed gas. They do not create motion on command, do not provide controlled stop/start behavior, and are not position-aware. They assist motion; they do not generate controlled motion.

Hydraulic cylinders

A hydraulic cylinder is typically only one part of a hydraulic system. It requires a pump, valves, fluid lines, and a reservoir/filtration system. Hydraulics excel at very high force and heavy continuous duty, but add system complexity and maintenance.

Pneumatic cylinders

Pneumatic cylinders rely on compressed air. They are often ideal for fast repetitive motion in industrial settings with existing air infrastructure, but typically require additional components for precise positioning and force control.

3. Types of Linear Actuators (Taxonomy)

Actuators are categorized by how they generate force. The right type depends on the environment, required force, speed, duty cycle, and control requirements.

Table of linear actuator types including DC, AC, hydraulic, and pneumatic.

Figure 3. Linear actuator selection taxonomy table. Categorizes actuators by power source (DC electric, AC electric, hydraulic, pneumatic, piezo) and lists best-use applications, key advantages, and engineering tradeoffs for automation and robotics.
Type Best For Key Advantages Key Tradeoffs
Electric (DC) Furniture, hatches, automation, robotics, vehicles, general positioning Simple power, clean, compact, controllable; feedback possible Force-speed tradeoff; duty cycle is thermally limited
Electric (AC) Industrial environments with AC power standards Robust options; plant-friendly wiring standards More complex safety/wiring; DC more common for compact systems
Hydraulic Very high force; heavy equipment; high load continuous duty High force density; smooth heavy-load performance Requires hydraulic system; maintenance/leaks; larger footprint
Pneumatic Fast repetitive industrial motion Fast cycles; simple cylinders Needs compressed air; less precise without extra components
Piezo / Voice Coil Micro-positioning, optics, precision small travel Very precise; fast response Short stroke; higher cost; specialized electronics

Key takeaway: For most consumer, commercial, and compact industrial applications, DC electric linear actuators provide the best balance of simplicity, control, cost, and performance.

4. The Fundamental Tradeoff: Force, Speed, and Duty Cycle

Force, speed, and duty cycle are linked. You cannot maximize all three at the same time. The actuator must operate within a mechanical and thermal performance envelope.

Graph showing the tradeoff between actuator force, speed, and duty cycle.
Figure 4. Engineering performance envelope graph for electric linear actuators. Visualizes the fundamental tradeoff where higher force results in lower speed, and defines the thermal safety limits determined by duty cycle and heat dissipation.

4.1 Force vs Speed (mechanical tradeoff)

Higher force typically requires greater gear reduction and/or a finer screw pitch. Both reduce output speed. Faster actuators generally produce less force, so there is always a Force vs Speed trade-off when selecting the ideal Actuator

Linear actuator force vs speed performance curve.
Figure 4A. Force-speed curve for DC linear actuators. Demonstrates how output speed naturally decreases as load increases, illustrating the mechanical relationship between motor torque, gear reduction, and screw pitch.

  • Higher force requires greater gear reduction and/or a finer screw pitch

  • Greater reduction lowers output speed

  • Faster actuators inherently produce less force

This tradeoff is fundamental to screw-driven systems:

  • A coarse screw pitch moves faster but generates less force

  • A fine screw pitch moves slower but generates higher force

This is why two actuators with the same motor size can have dramatically different force and speed ratings.


4.2 Duty cycle exists because heat limits motor life

As load increases, motor current increases, which increases heat. Many compact actuators rely on passive heat dissipation through the housing. Duty cycle ratings prevent overheating and premature wear.

Graph of motor current draw vs load and heat generation.
Figure 4B. Electrical characteristic graph showing linear actuator current draw rising linearly with applied load. highlights thermal risks where high loads lead to rapid motor heating and potential failure if duty cycle limits are exceeded.

As actuator load increases:

  • Motor current increases

  • Electrical losses rise

  • Heat builds in the motor, gears, and screw

Unlike industrial motors with active cooling, most compact electric actuators rely on passive heat dissipation through their housing.
Once internal temperatures exceed safe limits, damage or premature wear occurs.

Duty cycle ratings exist to prevent this.

4.3 What duty cycle means (practical definition)

Duty cycle is typically defined over a window (often 10 minutes). For example, 20% duty cycle means 2 minutes ON / 8 minutes OFF in that window. Actual allowable runtime depends on load, ambient temperature, and cooling conditions.

Diagram explaining 20% duty cycle: 2 minutes on, 8 minutes off.
Figure 4C. Visual explanation of linear actuator duty cycle ratings. Timeline diagram illustrating a 20% duty cycle example (2 minutes active time followed by 8 minutes cooling time) to prevent motor overheating and ensure longevity.

A duty cycle such as 20% does not mean:

  • 20% of the day

  • 20% of continuous operation

It means:

  • In a defined time window (often 10 minutes),

  • The actuator may run for 20% of that time,

  • And must rest for the remaining 80% to cool.

For example:

  • 2 minutes on

  • 8 minutes off

Actual allowable runtime depends on:

  • Load magnitude

  • Ambient temperature

  • Mounting orientation

  • Frequency of starts and stops

4.4 Why undersizing causes failures

Operating near maximum force pushes current toward stall levels, rapidly generating heat and accelerating wear. A modest safety margin typically improves reliability, consistency, and lifespan.

Operating near maximum force:

  • Pushes current toward stall levels

  • Rapidly generates heat

  • Reduces effective duty cycle

  • Accelerates wear of gears, bearings, and seals

Common symptoms include:

  • Slowing under load

  • Inconsistent motion

  • Thermal shutdown (if present)

  • Shortened service life

An actuator that appears “strong enough” on paper often fails in practice when friction, misalignment, or real-world loading are ignored.

4.5 The Engineering Rule of Thumb

Graph highlighting the safe operating zone for long actuator life.

Figure 4E Actuator sizing guide illustrating the "Engineering Rule of Thumb." Highlights the optimal operating region—typically 50-80% of rated capacity—where efficiency is highest and wear is minimized, avoiding the "danger zone" near stall force.

For long life and reliable performance:

  • Select an actuator so normal operation occurs well below maximum force

  • Avoid sustained operation near stall

  • Allow thermal headroom for environmental variation

A slightly oversized actuator runs cooler, quieter, and more consistently than one pushed to its limits.

This principle applies regardless of application — from furniture and hatches to automation and robotics.

5. The 7 Selection Criteria (Practical Decision Framework)

Reliable selection evaluates these seven criteria together. Optimizing one while ignoring others typically leads to compromised performance or early failure.

Checklist of 7 steps for selecting a linear actuator.
Figure 5. The 7-point engineering framework for selecting the correct linear actuator. Flowchart covering critical factors: Force, Stroke, Speed, Duty Cycle, Environment (IP rating), Noise levels, and Control feedback requirements.

5.1 Force

Force must include friction, starting loads, and geometry effects. Use a safety factor (often 1.5× to 2× for many real-world builds) to account for unknowns and worst-case conditions.

Diagram showing axial force loading on a linear actuator.
Figure 5.1. Visual guide for Actuator Selection Criteria #1: Force. Illustrates that force must be calculated including friction and gravity, and applied axially (in-line) to the actuator shaft to prevent side-loading damage

5.2 Stroke length

Stroke is actuator travel, not necessarily load travel. Hinges, linkages, and pulleys can change the relationship. Always confirm retracted/extended lengths fit your available space.

Linear actuator stroke length vs retracted and extended length.
Figure 5.1 Visual guide for Actuator Selection Criteria #2: Stroke. Distinguishes between "Stroke" (the travel distance) and the "Retracted/Extended Holes" (the physical space required to fit the device). Reminds designers to account for the device's physical housing, not just its movement.

5.3 Speed

Speed often drops under load. Choose speed for usability and safety (too fast can feel unsafe; too slow can feel unresponsive).

Speedometer icon representing linear actuator velocity selection.
Figure 5.3 Visual guide for Actuator Selection Criteria #3: Speed. Represents the selection of optimal travel speed. Highlights that speed usually drops as load increases, and that safer, controlled speeds are often preferable to maximum velocity.

5.4 Duty cycle

Duty cycle must match how often and how long the actuator runs. Higher loads and higher ambient temperatures reduce thermal margin.

chart representing duty cycle and cooling time.
Figure 5.4 Visual guide for Actuator Selection Criteria #4: Duty Cycle. Illustrates the ratio of "On Time" vs. "Cooling Time." Crucial for preventing motor overheating by ensuring the actuator rests sufficiently between cycles.

5.5 Environment (IP rating, corrosion, temperature)

Match sealing and materials to dust, water, temperature extremes, and corrosive exposure. IP rating is necessary but not the entire story—orientation and corrosion resistance matter too.

Weather chart representing IP rating and environmental protection.
Figure 5.5 Visual guide for Actuator Selection Criteria #5: Environment. Symbolizes the need to select the correct Ingress Protection (IP) rating for water, dust, and temperature ranges to prevent corrosion and internal electrical failure.

5.6 Noise

Noise is influenced by screw type, gearing, alignment, and mounting stiffness. Poor alignment increases noise and wear.

Sound wave icon representing actuator noise levels.
Figure 5.6 Visual guide for Actuator Selection Criteria #6: Noise. Indicates that noise is a system-level factor, influenced not just by the motor (dB rating) but by mounting resonance, vibration, and structural stiffness.

5.7 Control & feedback

Simple extend/retract can use basic switching. Repeatable stops, positioning, or multi-actuator lifting benefits strongly from feedback (Hall/pot) and appropriate control systems.

Controller diagram representing wiring and feedback options.
Figure 5.7 Visual guide for Actuator Selection Criteria #7: Control. Represents the choice between simple two-wire power (extend/retract) and advanced smart control using Hall Effect or Potentiometer feedback for precision positioning.

Section 5 takeaway

A reliable actuator selection evaluates all seven criteria together:

  • Force

  • Stroke

  • Speed

  • Duty cycle

  • Environment

  • Noise

  • Control & feedback

Optimizing one at the expense of others almost always leads to compromised performance.

6. Engineering Sizing Models (Real-World Calculations)

Correct sizing depends on how the actuator interacts with the load. Choose the model that matches your mechanism. The core sizing scenarios encountered in real actuator applications.
Rather than abstract formulas, these models focus on worst-case forces, geometry, and practical safety margins.

Diagrams showing push-pull, lift, hinge, and pulley actuator loading.
Figure 6. Overview of linear actuator sizing scenarios. Visualizes the four primary mechanical load types: Direct Push/Pull (axial), Vertical Lift, Hinged Pivot (torque), and Pulley/Cable systems. Used to identify which physics model applies to a specific engineering project.

6.1 Direct push/pull (axial load)

Required Force ≈ Load Resistance + Friction

This is the simplest case if the load is guided. Ensure the actuator is not acting as a guide rail.

Diagram of a linear actuator pushing a guided load axially
Figure 6A. Engineering model for "Direct Push/Pull" sizing. Shows an actuator pushing a load supported by linear rails or guides. Illustrates that when the load is guided, the actuator only overcomes friction and gravity, without bearing the weight directly.

 

This is the simplest and most forgiving case provided the load is properly guided.

Force model

Required force is approximately:

Required Force ≈ Load Force + Friction

Where:

  • Load force is the force resisting motion (weight component, resistance)

  • Friction includes guides, seals, bearings, and misalignment


6.2 Vertical lifting (gravity dominated)

Required Force ≈ Weight + Friction

Vertical builds fail most often due to side loads and racking. Use guide rails/columns so the actuator applies force only.

Diagram showing a linear actuator lifting a load vertically.
Figure 6B. Engineering model for Vertical Lifting. Visualizes the gravity-dominated sizing scenario where the actuator pushes directly against weight ($F = mg$). Notes that unlike horizontal sliding, there is no mechanical assistance—if power is lost, the load will reverse unless the actuator has a brake or high holding force

 

Vertical lifting introduces gravity as a constant load.
However, gravity alone is rarely the failure mode — side-loading is.

Force model

Required Force ≈ Weight + Friction

Critical design rule

The actuator must apply force only.
Guides must:

  • Carry lateral loads

  • Prevent racking

  • Maintain alignment throughout travel

Failure to guide vertical loads is one of the most common causes of bent rods and premature wear.


6.3 Hinged lids/hatches (moment-based)

Hinged systems require torque about the hinge. Required actuator force changes through the motion and is often highest near closed.

Hinge Torque Needed ≈ Weight × Distance to center of mass

The actuator must provide that torque through mounting geometry (angles and moment arms).

Geometry diagram showing hinge pivot, center of mass, and actuator angle
Figure 6C. Engineering model for Hinged/Pivot Loads. Displays the critical trigonometry for lifting hatches: the hinge pivot point, the load's center of mass, and the actuator mounting angle. Demonstrates that required force is a torque calculation ($\text{Force} \approx \text{Weight} \times \text{Distance}$) rather than a simple weight calculation.

In hinged systems:

  • The actuator does not lift weight directly

  • It produces torque about the hinge

  • Required force changes continuously through the motion

  • Key variables shown in Figure 6C

    • Hinge location

    • Load center of mass

    • Actuator mounting points

    • Perpendicular moment arm

    • Opening angle

    Core principle

    Required hinge torque ≈ Weight × Distance to center of mass

    The actuator must generate that torque through its mounting geometry.

    Because geometry changes with angle:

    • Force is often highest near the closed position

    • Small mounting changes can dramatically reduce force

    This is why hinged applications benefit from:

    • Geometry calculators

    • Physical mock-ups

    • Conservative safety margins


6.4 Force variation through motion

Many hatch failures occur because the actuator is sized for mid-stroke rather than worst-case near closed. Design for the peak requirement.

Graph showing actuator force decreasing as a hatch opens. 
Figure 6D. Force vs. Angle Curve for hinged applications. Visualizes why actuators need peak force at the "closed" position (0 degrees) where leverage is lowest. Explains why sizing based on "mid-stroke" average force often leads to stalling at the start of motion.

 

As you can see when the Actuator first starts to move the force is at its maximum because the leverage is at its least, but as the hatch opens up the force drops dramatically.

This explains a common failure pattern:

  • Actuator moves easily once opened

  • Struggles or stalls near fully closed

The worst-case force typically occurs:

  • At small opening angles

  • When the moment arm is shortest

Designing only for mid-stroke force is insufficient.


6.5 Pulley/cable systems (mechanical advantage)

If you multiply motion by N, you typically multiply required actuator force by approximately N (plus friction losses).

Comparison of 1:1 vs 2:1 pulley setups with linear actuators.
Figure 6E. Engineering model for Pulley & Cable Systems. Compares a standard 1:1 drive against a 2:1 mechanical advantage setup. Illustrates how pulleys trade travel distance for increased force (multiplying the load the actuator feels), requiring careful calculation of friction losses and stroke length.

Pulleys trade:

  • Travel for force

  • Or force for travel

Key rule

If the pulley system multiplies motion by N, the actuator must produce approximately N× the force
(plus friction losses).

Practical consequences

  • Pulleys increase actuator load

  • Friction compounds quickly

  • Safety margin becomes more important

Pulley systems are useful but should never be treated as “free force.”


6.6 Starting loads (static friction)

Starting force is often higher than running force due to static friction and seal preload. Size for the worst-case start condition.

Chart comparing high starting force vs lower running force.

Figure 6F Comparison of Static (Start) vs. Dynamic (Run) Friction. Highlights that the "break-away" force required to initiate movement is typically higher than the force needed to maintain motion due to seal preload and static friction, necessitating a sizing buffer.

Starting force is often higher than running force due to:

  • Static friction

  • Seal preload

  • System compliance

Sizing must always consider:

  • Worst-case start condition

  • Cold temperatures

  • Initial misalignment

An actuator that only meets running force may stall at startup.

6.7 Why Safety Factors Are Not Optional

Bar chart showing rated capacity vs actual load with safety margin.

Figure 6G Visual explanation of Engineering Safety Factors. Shows the "Operating Margin"—the necessary buffer between the actuator's maximum rating and the actual load. Recommends a 1.5x to 2x safety factor to account for real-world variables like wear, cold temperatures, and manufacturing tolerances.

Real systems include:

  • Manufacturing tolerances

  • Wear over time

  • Environmental variation

  • User behavior

A properly sized actuator operates comfortably inside its capability envelope.

Designing at the limit assumes a perfect world.
Engineering assumes the opposite.

Section 6 takeaway

  • Size based on load interaction, not just weight

  • Identify worst-case force positions

  • Guide loads — never side-load actuators

  • Hinged systems require geometry analysis

  • Pulley systems multiply force requirements

  • Always include safety margin

7. Mounting & Geometry (Why Most Actuators Fail)

Most field failures are caused by mounting errors, misalignment, and side loads—not by the actuator itself.

Linear actuator mounted with clevis pins allowing rotation.
Figure 7. Best practice for Linear Actuator Mounting. Shows how using pivot brackets (clevis mounts) on both ends allows the actuator to rotate through its arc of motion. This prevents destructive side-loading (binding) that occurs if an actuator is rigidly fixed while pushing a rotating load.

7.1 Golden rule: actuators are not guide rails

Linear actuators are designed for axial push/pull loads. Side loads cause binding, noise, seal wear, bent rods, and early failure.

Diagram comparing correct axial load vs incorrect side load.

Figure 7A. Visualizing the "Golden Rule" of linear actuator mounting: Actuators are not guide rails. This diagram illustrates that actuators are designed only for push/pull force. Using an actuator to support the weight of a load (side-loading) causes rod bending, seal failure, and permanent damage.

Linear actuators are designed to take load only along their axis (push/pull).
They are not designed to:

  • Support lateral forces

  • Prevent racking

  • Act as linear rails or columns

Consequences of side-loading

  • Bent extension rods

  • Excessive seal wear

  • Increased noise and vibration

  • Premature gearbox and bearing failure

These failures often appear “random,” but they are mechanical in origin.

Illustration of off-center loading causing friction and binding.
Figure 7c. Engineering image showing Eccentric Loading. Demonstrates what happens when the force is not applied directly in line with the center of the rod. Even a slight offset creates a "moment arm" that jams the shaft against the internal bearings, increasing friction and current draw significantly.
Most linear actuator failures are caused by mounting and geometry errors — not by the actuator itself.

Even a correctly sized actuator will fail prematurely if it is forced to carry loads it was never designed to handle.

7.2 Guide the load independently

Use rails/slides/columns/hinges to keep the load aligned. The actuator should apply force only.

Use rails/slides/columns/hinges to keep the load aligned. The actuator should apply force only.

The load must be guided independently using:

  • Linear rails

  • Drawer slides

  • Guide columns

  • Hinges or pivots designed to carry side loads

The actuator’s job is only to apply force, not to maintain alignment.

7.3 Use pivot mounts at both ends

Geometry changes through the stroke. Pivot mounts (clevis/rod ends) allow angular change without bending the actuator.

Linear actuator mounted with clevis pins allowing rotation.

Figure 7C. Best practice for Linear Actuator Mounting. Shows how using pivot brackets (clevis mounts) on both ends allows the actuator to rotate through its arc of motion. This prevents destructive side-loading (binding) that occurs if an actuator is rigidly fixed while pushing a rotating load like a hatch.

As the actuator extends and retracts:

  • Mounting angles change

  • Small arcs form

  • Rigid mounts introduce bending loads

Correct practice

  • Use clevis mounts, rod ends, or pivot brackets

  • Allow angular movement at both ends

  • Ensure the actuator can self-align through its stroke

Rigid, non-pivoting mounts are a frequent cause of hidden side loads.

7.4 Structural stiffness matters

Flexible brackets and thin panels deflect under load, creating dynamic misalignment and side loading. Reinforce mounts and reduce unsupported spans.

7.5 Hinged Applications: Mounting Location Matters More Than Force Rating

Diagram comparing short vs long moment arms on a hinged hatch.

Figure 7E. Visualizing Mechanical Advantage in Hinged Applications. Illustrates the trade-off between force and stroke. Mounting the actuator close to the hinge (short moment arm) requires significantly higher force. Moving the mounting point further away reduces the required force but increases the stroke length needed.

Small changes in:

  • Mounting distance from the hinge

  • Actuator angle

  • Anchor point height

can:

  • Cut required force dramatically

  • Reduce side loads

  • Improve smoothness near closed

Poor geometry often leads to oversized actuators being used to compensate — masking the real problem.

Section 7 takeaway

  • Linear actuators must never be side-loaded

  • Loads must be guided independently

  • Pivot mounts are essential

  • Geometry changes throughout the stroke

  • Structural stiffness matters

  • Common failure modes can ealisy happen

Correct mounting extends actuator life more than increasing force rating.

8. Common Failure Modes (and How to Avoid Them)

Nearly all actuator failures trace back to selection, sizing, mounting, environment mismatch, or control strategy.

Common Failures occure because of:

  • Actuator acting as a guide

  • Rigid mounts with no pivot

  • Off-axis loading

  • Flexible brackets

  • Poor hinge geometry

These mistakes account for the majority of warranty returns and field failures.

Chart identifying side loading, water ingress, and duty cycle failures.
Figure 8. 

Troubleshooting guide for Common Linear Actuator Failures. Visualizes the three primary causes of premature breakdown:

  1. Side-Loading: Bent rods caused by rigid mounting.

  2. Environmental Ingress: Water or dust damage due to incorrect IP rating or orientation.

  3. Thermal Overload: Motor burnout caused by exceeding the duty cycle.

Figure 8 summarizes the most common real-world linear actuator failures.
Almost all of them trace back to selection, sizing, or mounting errors rather than manufacturing defects.

8.1 Undersized force

Symptoms: stalling, slow movement, overheating, intermittent operation. Prevention: size for worst-case + friction + safety factor.

Linear actuator stalling under heavy load
Figure 8.1. Visualizes the symptoms of an Undersized Actuator: stalling, slow or sluggish movement, and rapid overheating. Highlights that prevention requires sizing for the "Worst-Case" load scenario + friction + a safety factor, rather than just the average weight.

What causes it

  • Ignoring friction and geometry

  • Designing for average instead of worst-case force

  • No safety margin

What it looks like

  • Actuator moves initially, then stalls

  • Sluggish motion under load

  • Excessive heat buildup

  • Premature motor or gearbox wear

How to prevent it

  • Size for worst-case conditions

  • Apply realistic safety factors

  • Avoid operating near stall torque

8.2 Side-loading / misalignment

Symptoms: noise, jerky motion, bent rod, seal wear. Prevention: guidance + pivot mounts + rigid structure.

Bent actuator rod and worn seals due to side loading.
Figure 8.2. Illustrates Mechanical Binding and Side Loading. Symptoms include jerky motion, grinding noise, bent rods, and premature seal wear. Prevention relies on using correct guidance (rails), pivot mounts (clevis), and ensuring the structure is rigid enough to prevent flexing.

What causes it

  • Actuator used as a guide

  • Rigid mounting without pivots

  • Flexible structures that deflect under load

What it looks like

  • Bent extension rod

  • Loud or jerky motion

  • Seal damage and accelerated wear

How to prevent it

  • Guide the load independently

  • Use pivot mounts at both ends

  • Ensure structural stiffness

8.3 Exceeding duty cycle (thermal overload)

Symptoms: intermittent stopping, reduced performance, shortened lifespan. Prevention: respect duty cycle, reduce load, increase thermal margin.

Overheated motor windings from exceeding duty cycle.
Figure 8.3. Depicts Thermal Overload caused by ignoring duty cycle ratings. Symptoms include intermittent stopping (thermal cutoff tripping), reduced performance, and burnt motor smell. Prevention involves strictly adhering to the On/Off cooling schedule (e.g., 2 minutes on, 8 minutes off).

What causes it

  • Frequent cycling without cooldown

  • High loads combined with short rest periods

  • Elevated ambient temperature

What it looks like

  • Actuator stops intermittently

  • Reduced speed after repeated cycles

  • Permanent loss of performance

How to prevent it

  • Respect duty cycle ratings

  • Reduce operating load

  • Increase actuator size or cooling margin

8.4 Environmental ingress/corrosion

Symptoms: contamination, rust, seal failure. Prevention: correct IP rating, corrosion resistance, protective orientation.

Rusted actuator components due to water ingress.
Figure 8.4. Shows the effects of Environmental Ingress (water or dust). Symptoms include internal rust, contamination, and electrical shorts. Prevention requires selecting the correct IP rating (e.g., IP66 or IP69K) and orienting the actuator so water drips away from the seal.

What causes it

  • Incorrect IP rating

  • Direct water spray or immersion

  • Corrosive environments (salt, chemicals)

What it looks like

  • Rusted rods

  • Internal contamination

  • Seal degradation

How to prevent it

  • Choose appropriate IP rating

  • Consider corrosion-resistant materials

  • Protect actuator orientation where possible

8.5 Poor control strategy

Symptoms: uneven lifting, racking, inconsistent stop points. Prevention: feedback + proper controller for precision/sync.

Uneven lifting and racking in a multi-actuator system.

Figure 8.5.  Visualizes Synchronization Failure in multi-actuator systems. Symptoms include uneven lifting, mechanical racking, and inconsistent stop points. Prevention requires using feedback sensors (Hall Effect) and a dedicated sync controller rather than simple open-loop switches.

What causes it

  • Parallel wiring without feedback

  • Load imbalance

  • Lack of synchronization control

What it looks like

  • Racking or twisting

  • One actuator leading

  • Structural damage over time

How to prevent it

  • Use feedback-based controllers

  • Design for symmetric loading

  • Monitor position rather than time

8.6 Power issues (voltage drop)

Symptoms: weak speed/force, instability, controller faults. Prevention: correct power supply and wire gauge, minimize voltage drop.

Chart showing voltage drop reducing actuator force.

Figure 8.6. Illustrates Power Supply Issues. Symptoms include weak force, unstable speed, and controller resets. Prevention involves using the correct wire gauge (thickness) to minimize voltage drop over long cable runs and ensuring the power supply can handle peak current spikes.

What causes it

  • Undersized wiring

  • Voltage drop under load

  • Inadequate power supply capacity

What it looks like

  • Reduced speed

  • Inconsistent operation

  • Controller faults

How to prevent it

  • Size wiring for current draw

  • Use appropriate power supplies

  • Minimize cable length where possible

Section 8 takeaway

Most linear actuator failures are preventable.

They result from:

  • Undersizing

  • Poor mounting

  • Ignoring thermal limits

  • Environmental mismatch

  • Inadequate control

When actuators fail early, the root cause is usually installation issues and design — not the actuator.

9. Control, Feedback, and Synchronization

Control architecture determines reliability for positioning, shared loads, and safety behavior. As actuator systems become more complex, control strategy matters as much as mechanical sizing

Flowchart from simple switches to synchronized feedback control.
Figure 9. Control hierarchy for actuator systems. Control spectrum (open loop switch → timed control → feedback closed-loop → synchronized multi-actuator).

9.1 Open-loop control (basic extend/retract)

Polarity reversal (DPDT switch or controller) drives extend/retract. Suitable when only end positions matter and loads are predictable.

Wiring diagram for a DPDT rocker switch with a linear actuator.

Figure 9.1.  Schematic for Basic Open-Loop Control. Shows how to wire a 2-wire DC actuator to a 6-pin DPDT (Double Pole Double Throw) switch. Reversing the polarity extends or retracts the unit; no complex electronics required.

How it works

  • Polarity reversal controls direction

  • Internal limit switches stop motion at end of stroke

  • No position awareness beyond fully extended or retracted

When it’s appropriate

  • Simple doors or hatches

  • Occasional use

  • No need for repeatable intermediate positions

Limitations

  • No position feedback

  • No load balancing

  • Cannot compensate for drift or wear

Open-loop control assumes everything behaves perfectly every time — which is rarely true in real systems.

9.2 Timed control (pseudo-positioning)

Runs the actuator for a set time. Inaccurate when load/voltage varies; use only for low-risk applications where drift is acceptable.

diagram to show timed control of actuators using relays or timers.

Figure 9.2. Diagram to show timed control using a timer relays controller.

How it works

  • Actuator runs for a set duration

  • Assumes consistent speed and load

Where it fails

  • Speed changes with load

  • Voltage variation alters timing

  • Wear accumulates over time

Timed control is sometimes used for low-cost systems, but it is inherently imprecise, but for some applications like opening and closing a cattle feeder, this level of Actuator timer control is more than adequate.

9.3 Feedback (Hall sensor or potentiometer)

Enables repeatable intermediate positions, position awareness, and error correction. Strongly recommended for precision or synchronization.

Figure 9C shows actuators equipped with position feedback.

Figure 9.3. Technical illustration of Position Feedback. Shows how Hall Effect sensors or Potentiometers are integrated into the motor or gearbox. These sensors count rotations to tell the controller exactly where the actuator is, enabling memory presets and synchronization.

Common feedback methods

  • Hall sensors (digital pulse output)

  • Potentiometers (analog position signal)

What feedback enables

  • Repeatable intermediate positions

  • Accurate stopping points

  • Compensation for load and speed variation

  • Monitoring of actuator health

Feedback transforms an actuator from a “blind mover” into a position-aware system component.

9.4 Synchronization (multi-actuator lifting)

Parallel wiring rarely stays aligned under real loads. Feedback-based synchronization compares positions and continuously corrects differences to prevent racking.

Wiring diagram connecting multiple actuators to a FCB-2 sync controller

Figure 9.4.  Schematic for Multi-Actuator Synchronization. Illustrates the "Master/Slave" or centralized control architecture (like the Firgelli FCB-1). The controller reads feedback pulses from 2-4 actuators simultaneously and adjusts power to keep them perfectly aligned, preventing mechanical racking.

How it works

  • Controller monitors position feedback

  • Motion is adjusted in real time

  • Errors are corrected automatically

Benefits

  • Consistent positioning

  • Smooth acceleration and deceleration

  • Reduced mechanical stress

  • Improved longevity

Closed-loop control is essential for applications where precision or repeatability matters.

Section 9 takeaway

  • Control complexity should match application risk

  • Open-loop systems assume perfection

  • Feedback enables precision and reliability

  • Synchronization prevents racking and mechanical damage

  • Safety requires redundancy

A well-controlled actuator system lasts longer, performs better, and fails more gracefully.

10. End-to-End Actuator Selection Flow

Use this flow before purchasing or fabricating mounts. It prevents the most common “it worked on paper” failures.

Quadrant chart classifying applications by risk and load guidance
Figure 10. A decision tool for engineers to classify their project.
  1. Define the motion type: push/pull, lift, hinge, pulley/cable.
  2. Confirm the load is guided: add rails/slides if required.
  3. Compute worst-case force: include friction, start loads, and geometry.
  4. Apply safety margin: typically 1.5×–2× for many real-world builds.
  5. Confirm stroke: travel + packaging constraints (retracted/extended length).
  6. Confirm speed at load: usability and safety.
  7. Confirm duty cycle: thermal limits for expected use.
  8. Match environment: IP rating and corrosion resistance.
  9. Select control strategy: switch vs feedback vs synchronization.
  10. Validate geometry: pivot mounts, stiffness, alignment through motion.
Linear Actuator Safe Operating Envelope Chart: Force vs. Speed Check
Figure 10.1. Engineering chart, titled "Figure 10.1. Envelope check," plotting Force (Y-axis) versus Speed (X-axis) to define a linear actuator's performance capabilities. A green shaded area labeled "SAFE OPERATING REGION (PASS)" shows the acceptable combination of force and speed, bounded by the "Max Force Limit" and the actuator's performance limit curve. The red area outside this curve is the "UNSAFE REGION (FAIL)." A data point labeled "Application Requirement" is marked inside the green zone, indicating a properly sized actuator for that specific application.

10.1 Application Classification

Application Classification diagram for electric linear actuators showing motion types (push, pull, lift, hinge), load behavior (guided vs unguided), and risk levels (cosmetic vs safety-critical)

Figure 10.1. Application Classification for Electric Linear Actuators (Diagram illustrating motion types, load behavior, and risk levels to guide sizing and control strategy decisions

Start by identifying:

  • Motion type: push/pull, lift, hinge, cable

  • Load behavior: guided vs unguided

  • Risk level: cosmetic vs safety-critical

This classification determines how conservative your sizing and control strategy must be.

10.2 Mechanical Path Decision


Mechanical Path Decision chart

Figure 10.2. distinguishes guided from unguided systems.

  • If the load is not guided, add guidance before proceeding.

  • If multiple actuators share a load, assume synchronization is required.

This step eliminates the most common mechanical failure modes early.

10.3 Performance Envelope Check


Overlays required force and speed against duty cycle limits.

Figure 10.3. Overlays required force and speed against duty cycle limits.

Proceed only if:

  • Required force lies comfortably below rated force

  • Required speed is achievable at load

  • Duty cycle remains within thermal limits

If any boundary is exceeded, revise geometry or select a higher-capacity actuator.

10.4 Control Architecture Selection

Diagram showing how application requirements determine control architecture, from open-loop motion to feedback, synchronized closed-loop control, and layered safety protection.

Figure 10.4. maps application needs to control strategy.

  • End-to-end motion only → open loop

  • Repeatable stops → feedback

  • Shared loads → synchronized closed loop

  • Safety-critical → layered protection

Control decisions should be finalized before wiring or fabrication begins.

Section 10 takeaway

  • Selection is a process, not a single spec

  • Early classification prevents late redesign

  • Mechanical, thermal, and control limits must all align

  • The correct actuator is the one that fits the system — not just the load

11. Frequently Asked Questions (FAQ)

These are the exact questions builders and engineers ask when selecting actuators.

11.1 What size linear actuator do I need?

Compute worst-case force (including friction and geometry), apply a safety factor, then confirm speed and duty cycle at that load. If any parameter is marginal, oversize or revise geometry/guidance.

11.2 How much force is required to lift a hatch?

Hatches are torque problems. Required force depends heavily on mounting location and changes throughout motion. Force is often highest near closed. Validate geometry using a calculator or mock-up and design for the peak requirement.

11.3 What stroke length do I need?

Stroke is actuator travel, not necessarily load travel. Hinges/linkages/pulleys change the relationship. Confirm retracted and extended length constraints before purchase.

11.4 What duty cycle do I need?

Duty cycle must match how often and how long the actuator runs. Frequent cycling and high loads require more thermal margin. When in doubt, operate well below maximum load and allow cooling time.

11.5 Can I run two or four actuators together?

Yes—but shared loads frequently rack without synchronization. Use feedback-based control and symmetric mounting. Parallel wiring is rarely reliable under real load variation.

11.6 Do I need feedback?

You need feedback if you want repeatable stops, intermediate positions, shared-load lifting, or position-aware safety behavior. Without feedback, systems drift as load and conditions change.

12. Summary, Charts, and Reference Checklist

This section condenses the entire guide into a fast reference. If you remember only one thing: actuators are system components—mechanics, heat, geometry, and control must all align.

One-page engineering reference chart for linear actuator selection, summarizing force, stroke, duty cycle, sizing cases, and control options in a single visual guide.
Figure 12. One-page reference summary for actuator selection.

12.1 Reference Checklist

  • ☐ Load is guided (actuator is not a guide rail)
  • ☐ Worst-case force identified (start condition + friction + geometry)
  • ☐ Safety factor applied (commonly 1.5×–2× for real builds)
  • ☐ Stroke confirmed (travel + retracted/extended fit)
  • ☐ Speed acceptable at operating load
  • ☐ Duty cycle respected (thermal margin confirmed)
  • ☐ Environment matched (IP rating + corrosion resistance)
  • ☐ Mounting uses pivots at both ends and stays aligned through stroke
  • ☐ Structure is stiff (brackets and frames do not flex under load)
  • ☐ Power supply and wiring sized to avoid voltage drop
  • ☐ Control strategy chosen (open loop vs feedback vs synchronization)
  • ☐ Safety layers included as required (limits, current control, E-stop)

 

12.3 Final principle

A correctly selected actuator is one that fits the system: mechanics + thermal limits + geometry + environment + control. When these match, actuators perform reliably for years instead of weeks.