Captive, non-captive and external-nut designs all convert stepper-motor rotation into linear motion, but they manage the screw, nut and anti-rotation function differently. The correct choice depends on the machine structure—not only the motor frame size.
Captive stepper motor linear actuator
A captive design includes an anti-rotation mechanism so the output shaft extends and retracts without requiring the machine to prevent shaft rotation. It can simplify integration for compact, short-stroke mechanisms.
Evaluate: available stroke, side-load limits, output-shaft support, installation length and required environmental protection.
Non-captive stepper motor linear actuator
In a non-captive design, the lead screw passes through a rotating nut inside the motor. The screw must be prevented from rotating by the load or external mechanism. This arrangement can support longer travel without a permanently projecting screw on only one side of the motor.
Evaluate: external anti-rotation, screw support, critical speed, alignment and the space required on both sides of the motor.
External-nut stepper motor linear actuator
In an external-nut design, the motor rotates the lead screw and a nut travels along it. The nut or connected load must be guided and prevented from rotating. This configuration is commonly integrated into linear stages, XY tables and positioning mechanisms.
Evaluate: guide arrangement, screw support, nut mounting, protective covers and the total installed length.
Comparison checklist
- Required stroke, speed and axial load
- Available installation envelope
- Existing external guide and anti-rotation method
- Screw lead, backlash and repeatability target
- Duty cycle, environment and expected service life
- Motor winding, drive voltage, connector and feedback
Share these requirements with Xinding to compare captive, non-captive and external-nut lead screw stepper motor linear actuator options for your application.