A linear motor is a direct-drive electromagnetic actuator that produces linear thrust between a stationary primary (winding stack) and a moving secondary (magnet track), with no ball screw, belt, or rack-and-pinion in the force path [S1][S5].
Industrial product lines now span continuous force from about 24 N in compact ironless stages to 2280 N in iron-core industrial units, with peak force ratings of 53 N to 6000 N, intermediate circuit voltage 110 V to 560 V DC, and maximum travel lengths up to 5800 mm at speeds to 5 m/s [S2][S3].
Four-axis selection framework used by machine builders
Buyers should evaluate four dimensions in order: motion requirements, load conditions, installation constraints, and precision demands, with motion and load driving the force class before any precision discussion [S1].
Load carries three sub-parameters, axial load, radial load, and overturning moment, and these directly set the thrust class, while load inertia must be matched against the motor mover inertia to keep response and positioning accuracy inside spec [S1]. Motion performance then needs rated thrust sized for steady-state, peak thrust sized for acceleration through F=ma, maximum speed, and a stated acceleration profile, all read against the motor's published speed-thrust curve [S1]. A buyer who skips this curve and only looks at nameplate force will routinely oversize or undersize the drive.
Ironless vs iron-core: a criteria-based comparison
Ironless linear motors show zero cogging and no magnetic attraction between primary and secondary, so they deliver smoother motion for semiconductor, laser cutting, and metrology stages, but their continuous force typically stays in the single-digit to low hundreds of newtons [S5].
Iron-core linear motors trade cogging and attraction force for higher force density, with real iron-core stages reaching continuous force above 230 N and peak force beyond 600 N on standard machine-builder datasheets [S5]. A representative iron-core platform, the CFX17, posts continuous thrust 76 N to 303 N and peak thrust 178 N to 712 N at 5 m/s, while the larger CFX25 reaches continuous 689 N to 1378 N and peak 1617 N to 3234 N over a 129 mm to 5633 mm stroke [S3]. For an ironless reference, the CFX10 frame covers continuous 24 N to 96 N and peak 53 N to 214 N at 3 m/s, with maximum travel to 3812 mm [S3].
Integrated stages bundle the motor with a linear guide and a linear encoder, and high-precision integrated platforms reach ±1 µm repeatability with optical or magnetic scales [S5]. Buyers who want a turnkey axis should confirm that the integrated package, not just the bare motor, hits the required repeatability under load.
Precision, feedback, and the linear-encoder dependency
Positioning accuracy, repeatability, and resolution are not motor-intrinsic; they are set by the feedback device, the drive loop, and the mechanical loop stiffness [S1].
Typical industrial linear-motor systems reach position repeatability of ±0.01 mm with a standard linear encoder, while high-end stages with grating encoders resolve to 0.5 µm, and feedback resolution in the 0.001 mm to 0.005 mm band is common for precision stages [S4][S5]. A buyer who needs sub-micron repeatability should budget for a high-resolution linear encoder, a matched servo drive, and a thermally stable machine base, because no amount of motor selection can compensate for encoder or structural drift. For applications where stroke and force are the gating specs, a standard ±0.01 mm loop is the realistic baseline.
Installation, environment, and thermal limits
Installation constraints cover allowable length, width, height, and mounting interface, and they must be checked against the application envelope before any force calculation [S1].
Environmental parameters, working temperature, humidity, dust, and corrosive gas, set the IP rating and housing material, and industrial reference designs operate from -20 °C to +60 °C with protection class IP54 to IP65 per IEC 60529 (IP65 for dust and water jets) [S4]. Continuous force is a thermal rating, and suppliers such as KML publish it at a heat-sink temperature of 20 °C with a ±10% spec tolerance [S2]. Buyers who mount the motor in an enclosed panel, in a hot cabinet, or with restricted convection should derate the published continuous force or specify forced-air or water cooling, otherwise the motor will trip thermal protection during a long duty cycle.
Drive, control, and integration checklist
Drive voltage and current must match the available DC bus, and common industrial linear motors run on an intermediate circuit voltage of 110 V to 560 V DC [S2].
Supply voltage on smaller framed units is often 24 V to 48 V DC, with 48 V used for higher-power models, and maximum current on a single stage can reach 5 A to 20 A peak at stall [S4]. The control interface must align with the host controller, and real platforms support pulse/direction, analog command, or fieldbus such as Profinet or EtherCAT, with EtherCAT dominant on European-built high-end stages [S1][S5]. A spec should lock the fieldbus protocol and the cycle time, not just the connector, because a mismatched drive bus can force a complete control-architecture redesign late in the project. For buyers sourcing a complete linear module rather than a bare motor, the same bus, drive, and feedback must all be compatible.
Who should NOT pick a linear motor, and what to pick instead
A linear motor is the wrong choice when the duty cycle is light, the required repeatability is ≥0.1 mm, and the budget cannot absorb the higher drive cost, the more complex commissioning, and the heat-dissipation design [S5].
For these duties, a linear actuator with a ball screw or a belt drive, or a linear bearing-guided leadscrew stage, is a better fit because it is cheaper, simpler to commission, and self-locking. Linear motors also struggle in dirty, high-vibration outdoor sites where iron filings or water ingress defeat the open magnetic track, so a sealed ball-screw actuator is the safer pick in those environments. Within the linear-motor family, an ironless stage is the wrong pick for a 500 kg moving mass; the cogging-free benefit does not pay back the extra cost when force density is the bottleneck, and an iron-core stage with a properly sized servo drive is the correct answer.
Shortlist logic and watch-points for 2026 procurement
A clean 2026 shortlist starts by mapping continuous force and peak force to the application's payload, acceleration, and duty cycle, then filters by stroke, encoder resolution, IP rating, and bus protocol, with thermal derating verified against the panel temperature [S1][S4].
Watch the supply voltage, because 48 V DC units are increasingly specified for safer cabinet integration, and watch the encoder interface, because a switch from analogue to digital scales on existing OEM platforms is the most common mid-cycle change request in machine-builder procurement (2025-12) [S5]. For a related decision tree on rotary drive selection, see the VFD-duty motor spec, cable, and cost gates guide, and for hazardous-area motor certification trade-offs, the explosion-proof motor suppliers 2026 map provides a parallel frame and certification cut.