A linear solenoid and an electric linear actuator both produce straight-line motion, but their force, control, and duty profiles diverge sharply once the stroke reaches the 20 mm class. Solenoids in industrial trim are commonly offered in 5-20 mm stroke with 5-120 N of force, while electric actuators scale into hundreds of newtons and beyond with closed-loop position control [S1][S3].
The headline rule: a 20 mm stroke falls inside the upper end of the solenoid envelope, so the swap is mechanically feasible, but only if the application can tolerate the solenoid's binary on/off behaviour, non-linear force curve, and limited holding force at the end of travel [S3][S6].
Force and stroke envelope at 20 mm
Industrial linear solenoid lines such as Kendrion's High Performance Solenoids span 5-20 mm stroke and 5-120 N force, which puts 20 mm at the maximum published stroke rather than a mid-range value [S1]. For light-duty tasks, a pull-type or push-type solenoid at 20 mm can deliver tens of newtons near the start of stroke, with force dropping as the plunger closes the air gap [S3][S4].
Electric linear actuators of the lead-screw and ball-screw families cover 20 mm strokes as a small fraction of their typical 50-300 mm range, with force limited mainly by the gearbox and screw lead rather than by magnetic saturation [S3]. A direct comparison at 20 mm: a solenoid can pull 50-120 N but only at a fixed end position, while a 12 V lead-screw actuator can hold 50-200 N anywhere along the stroke via the lead screw's mechanical advantage [S3][S2].
Motion profile: binary on/off vs controllable position
A linear solenoid operates as an electromagnetic device that produces linear motion when its coil is energised, with a return spring restoring the plunger when current is removed, giving true two-state behaviour by default [S3][S4]. Proportional solenoids exist, but they require closed-loop current control and still cannot hold a precise mid-stroke position the way a geared actuator can [S4].
An electric linear actuator is a motor, gearbox, and screw drive package, with ball-screw, roller-screw, and lead-screw variants giving precise positioning, variable speed, and high load capacity, attributes a spring-return solenoid cannot match [S3]. If the 20 mm task needs to stop at 5 mm, 12 mm, or 18 mm under closed-loop control, the actuator wins outright; the solenoid only has two legal positions, fully extended or fully retracted [S3][S4].
Power, duty cycle, and thermal limits
Solenoids consume power only when the coil is energised, which makes them more energy-efficient for short, intermittent tasks, but continuous duty drives the coil toward thermal limits and reduces force output as resistance rises [S3][S4]. Electric actuators consume more power because the motor runs throughout the stroke, but the thermal mass of the motor and gearbox typically permits 25-100 percent duty depending on sizing [S3].
For a 20 mm stroke cycling every few seconds, both technologies are thermally viable, but the solenoid's simpler construction and fewer moving parts translate into a longer mechanical life on simple on/off duty, while actuators win where holding torque at intermediate positions matters [S3][S5].
Decision criteria: solenoid, actuator, or voice coil
The table below lines the three main 20 mm-stroke options up against the criteria that actually drive a swap decision. Voice-coil actuators are included because the force-stroke curve is far flatter than a solenoid's, and experienced builders routinely point to them when a solenoid feels marginal [S6].
Criterion 1, load force: solenoids 5-120 N, voice coils 10-500+ N linear across stroke, electric actuators 50-2000+ N via screw mechanical advantage [S1][S3][S6]. Criterion 2, position control: solenoid binary or proportional, voice coil analog with position feedback, electric actuator fully programmable with encoder or potentiometer [S3][S4]. Criterion 3, holding force at mid-stroke: solenoid near zero (spring only), voice coil proportional to current, electric actuator full holding torque via lead screw [S3][S6]. Criterion 4, life and duty: solenoid 1-10 million cycles on light duty, voice coil similar, electric actuator 10,000-100,000 cycles on ball-screw and higher on lead-screw [S3][S5].
When the solenoid swap works at 20 mm
Use a linear solenoid at 20 mm when the load is under 100 N, the motion is binary, the duty cycle is below roughly 10 percent, and the return spring on the load side is acceptable. A solenoid valve on a pneumatic pilot loop is the canonical example: the 20 mm plunger only has to shift a small valve poppet, not a heavy mechanical load [S3][S4].
Packaging machinery, door-latch actuators, and small parts sortation also fit, because the 5-20 mm stroke window matches the 20 mm requirement and the 5-120 N force window matches light clamping or indexing duty [S1][S4]. For broader context on adjacent motion control topics such as coupling selection for precision axes, see the related article on bellows vs beam vs Oldham coupling stiffness.
When the actuator stays
Keep the electric linear actuator when the load needs more than 100 N of force, when mid-stroke holding is required, when speed must be variable between 1 mm/s and 50 mm/s, or when a CAN-bus or analog control signal must command position rather than just energise a coil. A real Digi-Key tech-forum case from May 2025 asked for an actuator delivering 500 lb (about 2,200 N) of spring-return force over a 25 mm stroke in 1-1.5 seconds on a 12 V, 2 A bus, well outside any solenoid's envelope [S2].
Integrated electric linear motor packages such as the ORCA series are also positioning themselves as drop-in replacements for pneumatics, with higher repeatability, lower maintenance, programmability, and precision, the same advantages that apply over solenoids on demanding 20 mm tasks [S5]. For a wider view of actuator selection on industrial duty, the related piece on mixed-SKU end-of-line sortation cell architecture covers EOAT and throughput trade-offs that sit downstream of the 20 mm motion decision.
Failure modes and limits to watch
Solenoid force vs stroke is highly non-linear with the highest force at the end of travel, so a 20 mm stroke that needs real work done at 10 mm will not deliver it; the device is sized for end-of-stroke work, which is the opposite of a lead-screw actuator whose usable force is roughly constant across the stroke [S6]. De-energising the coil collapses the magnetic field, so any position held must be held by the load or by an external spring, not by the solenoid itself [S4].
Continuous energisation heats the coil, drops force, and eventually trips thermal protection, so a 100 percent duty 20 mm solenoid is essentially a misuse case; an actuator with a proper motor and gearbox is the right tool for that profile [S3][S4]. Humidity, dust, and contamination can also affect the plunger bore on solenoids far more than on a sealed actuator, so outdoor or washdown environments may push the choice toward the actuator even at 20 mm [S5].
Signals to track
Two trackable signals: first, proportional and latching solenoid variants continue to extend the on/off device into mid-stroke territory with current feedback, so any datasheet revision showing 5-15 N holding force at 10 mm stroke would shift the swap threshold downward. Second, integrated electric linear motor product families such as the ORCA series are adding CAN-bus and programmable I/O on strokes as short as 20 mm, which tightens the actuator's grip on the lower end of the stroke range [S5].
For a broader industrial view covering welding, conveyors, and pumps alongside motion control, the stainless steel procurement pulse for 2026-09-22 and the arc welding plant transformer duty specification pieces sit in the same specification-driven frame.