How to Choose Linear Motors for Your Application?
Choosing a linear motor is not simply a matter of buying more speed. The right choice depends on the load, travel distance, duty cycle, accuracy, and operating environment. A compact ironless motor may suit a clean inspection stage, while a high-force iron-core design may better handle heavier loads. In either case, heat, cabling, and mounting space can change the result. Small details matter.
The International Federation of Robotics’ World Robotics 2024 report recorded 541,302 industrial robot installations worldwide in 2023, with the global operational stock reaching about 4.28 million units. These figures do not measure linear motor sales. They do, however, show the scale of automation environments where precise, repeatable motion matters. Linear motor applications range from semiconductor handling and packaging to machine tools and laboratory equipment, but each has different performance demands. A published peak-speed figure alone cannot tell you whether a motor will meet your real operating needs.
This guide explains how to compare force, speed, stroke, feedback, cooling, and controls before selecting a system. It also considers total cost, including the drive, encoder, installation, and maintenance—not just the motor itself. Ask suppliers for performance data under conditions close to your own, such as the actual payload and duty cycle. A spreadsheet can still mislead. I would treat any selection based on one headline specification as provisional; real applications often expose trade-offs that a catalogue does not.
Define the Motion Profile: Stroke, Speed, Acceleration, and Duty Cycle
A linear motor should be sized around the complete motion profile, not peak speed alone. Record the stroke, travel time, acceleration, deceleration, payload, and pauses between moves. For example, a 300 mm stroke completed in 0.4 seconds may demand far more force during acceleration than steady travel suggests. Include the mass of fixtures and cables; they are easy to overlook. Small details matter.
Estimate peak force and RMS force across the full cycle, then check the motor’s thermal limits at the planned duty cycle. Frequent short moves can produce substantial heating, even when average speed seems modest. The International Energy Agency’s 2011 report, Energy-Efficiency Policy Opportunities for Electric Motor-Driven Systems, estimates that motor-driven systems use about 46% of global electricity. That figure is not specific to linear motors, but it underlines why efficient, properly sized motion systems matter. A calculation can still miss real-world friction or changing payloads, so validate the profile under actual operating conditions.
Tips: Plot position, speed, and acceleration over one full cycle. Specify dwell time and cycles per hour, not just “continuous duty.” Leave margin for load variation, but avoid oversizing without a thermal or force calculation. It is tempting to trust the first spreadsheet. Check it against measured data.
How to Choose Linear Motors for Your Application? - Define the Motion Profile: Stroke, Speed, Acceleration, and Duty Cycle
| Example Application |
Stroke |
Peak Speed |
Peak Acceleration |
Duty Cycle |
Typical Motion Profile |
Selection Consideration |
| Precision inspection stage |
100 mm |
0.5 m/s |
5 m/s² |
20% |
Short moves with controlled acceleration, settling, and dwell at inspection points. |
Prioritize smooth low-speed motion, repeatability, and settling time. |
| Automated pick-and-place axis |
300 mm |
2.0 m/s |
20 m/s² |
60% |
Frequent point-to-point moves with rapid acceleration and brief dwell periods. |
Check peak force for the moving mass and RMS force over the full cycle. |
| Packaging machine indexing axis |
150 mm |
1.5 m/s |
15 m/s² |
80% |
Repeated index moves coordinated with a continuous production cycle. |
Assess thermal performance at the actual cycle rate and ambient temperature. |
| Long-travel material transfer |
1,200 mm |
2.5 m/s |
10 m/s² |
50% |
Long traverses with acceleration, a sustained travel segment, and return motion. |
Confirm available travel, cable or feedback arrangements, and maximum speed limits. |
| High-throughput sorting axis |
500 mm |
3.0 m/s |
30 m/s² |
75% |
Rapid bidirectional movements with frequent reversals and short pauses. |
Verify peak thrust, moving-load stiffness, and heat dissipation under repeated reversals. |
Note: These figures are illustrative application profiles, not motor ratings. Confirm the complete move-and-dwell cycle, payload and moving mass, required force, positioning accuracy, and thermal limits before selecting a motor.
Calculate Thrust with F = m·a + Resistance; Check Peak and RMS Force
How to Choose Linear Motors for Your Application?
Estimate thrust from the actual moving load, not just the payload. Use F = m·a + resistance, with mass in kilograms and acceleration in meters per second squared. A 12 kg carriage accelerating at 2 m/s² needs 24 N before friction, cable drag, or process forces are added. Measure resistance where possible; guide friction can change with alignment and temperature. The calculation is a starting point, not a guarantee.
Check peak force and RMS force separately. Peak force must cover short acceleration bursts, vertical loads, and other brief demands. RMS force reflects the heating effect of the motion cycle and should stay within the motor’s continuous rating. For example, a fast move followed by a long pause may have a high peak but modest RMS demand. Repeated rapid moves can raise RMS force quickly. Real motion profiles are often messier than the spreadsheet suggests.
Tips: Record the full move-and-dwell cycle, including payload changes and emergency stops. Add a sensible margin for uncertain resistance, but avoid oversizing without reason. Compare calculated forces with the motor’s force-speed limits and thermal ratings. If the carriage hesitates or runs warmer than expected, revisit the assumptions and measurements. There is usually one detail you missed.
Compare Iron-Core and Ironless Designs by Cogging, Heat, and Force Density
How to Choose Linear Motors for Your Application?
Iron-core and ironless linear motors behave differently under real loads. Iron-core designs use teeth and laminated steel, which can create cogging: small force variations felt as a slight ripple during slow motion. That ripple may matter when scanning a surface or positioning a camera. Ironless designs avoid iron-to-magnet attraction, so motion is typically smoother at low speeds. Still, bearing friction, alignment, and control tuning can affect smoothness too.
Heat changes the decision. Iron-core motors often deliver high force in a compact footprint, but their iron can add losses and attract debris in some environments. Ironless motors have no iron teeth, yet their coils still heat up during sustained operation. Check the duty cycle. A motor that handles short bursts may struggle through repeated, slow moves. Review coil temperature limits and provide a clear path for heat to escape, especially inside a sealed machine.
Force density is useful, but it is not the whole story. Iron-core designs can offer strong thrust for their size, which helps when space is tight or payloads are heavy. Ironless designs may suit applications where low cogging and a light moving assembly matter more than peak force. Compare continuous force, not just peak ratings, and include the carriage, cables, and cooling hardware in your estimates. A simple ranking can mislead. I would test the shortlisted motor at the actual speed and load; bench results rarely capture every installation detail.
Match Motor Speed to Drive Voltage and Back-EMF Limits
Choosing a linear motor begins with speed, voltage, and back-EMF. The relationship is direct: higher speed creates higher back-EMF. The drive must provide enough voltage for both resistance losses and motion-induced voltage. A practical estimate is Vrequired = Ke × speed + I × resistance. Ke is the motor’s back-EMF constant. Do not size from peak speed alone.
I once selected a motor using its advertised speed, then discovered the drive had limited voltage headroom. The carriage reached its target slowly. A neat spreadsheet can still lie. Leave roughly 10–20% voltage margin after accounting for cable drops, temperature, and current ripple. Confirm the drive’s continuous and peak current ratings, too. The U.S. Department of Energy’s 2022 Motor Systems Market Assessment highlights motor-driven equipment as a major portion of manufacturing electricity use. Small efficiency losses can therefore become expensive at scale. The International Energy Agency has also reported that electric motor systems consume about 46% of global electricity, making correct matching more than a motion-control detail.
Check the motor’s Ke in the actual unit system. Some datasheets use volts per meter per second; others use volts per revolution per minute. That mismatch can create a tenfold error. Test acceleration at the highest load and lowest supply voltage. Watch the drive bus with an oscilloscope. If the commanded speed approaches the back-EMF limit, reduce acceleration, increase available voltage, or choose a motor with a lower Ke. Do not assume field weakening will rescue every design. It may reduce force. The trade-off is easy to underestimate.
How to Choose Linear Motors for Your Application?
Match Motor Speed to Drive Voltage and Back-EMF Limits
The chart compares the drive DC-bus voltage with the motor back-EMF generated at the target linear speed.
Back-EMF is estimated using E = Ke × v. A practical design check is to keep the operating back-EMF below the available drive voltage with sufficient margin for current control, acceleration, and voltage drop.
Verify Cooling, Position Feedback, and Encoder Resolution of 1 µm or Finer
How to Choose Linear Motors for Your Application?
Verify Cooling, Position Feedback, and Encoder Resolution of 1 µm or Finer
Cooling is often the first practical test for a linear motor. Heat changes geometry. Continuous acceleration creates heat in the coil and nearby structure. Select forced-air or liquid cooling when duty cycles are demanding. Check the rated temperature, cooling capacity, and installation space. A motor that performs well for ten minutes may drift during an eight-hour shift. I once focused too heavily on peak force and underestimated thermal movement. That choice required later tuning and mechanical changes.
Position feedback deserves equal attention. A linear encoder with 1 µm resolution or finer can support precise motion, but resolution is not accuracy. Resolution is not accuracy. Scale quality, mounting errors, vibration, and controller performance also affect the final position. Review accuracy, repeatability, interpolation error, and signal stability together. The encoder should match the application’s stroke length and environmental conditions. Dust, oil mist, and temperature changes can degrade measurement reliability.
During evaluation, run the motor through the real motion profile. Measure drift after repeated cycles, not only during a short demonstration. Watch the encoder signal while the carriage reverses direction. Small errors often appear there. Confirm the feedback update rate and control-loop bandwidth with the system integrator. A finer encoder may expose mechanical weaknesses instead of solving them. This part is easy to overlook. Leave room for imperfect assumptions, because real machines rarely behave like laboratory models.
