Converting the rotary motion of a stepping motor into linear motion can be accomplished by several mechanical means, including rack and pinion, belts and pulleys and other mechanical linkages. All of these designs require various mechanical components. The most effective way to accomplish this conversion is within the linear actuator itself.


The basic stepper motor creates rotary motion of a magnet rotor core through the uses of pulses and electromagnetic field passing around the core. Linear actuators convert this rotational motion into a linear motion, with the precise dependent of the step angle of the rotor and the method chosen to accomplish the conversion. The linear stepping motor, or linear actuator, first came into being in 1968 under patent number 3,402,308, issued to William Henschke. Since this time, the linear actuator has found its way into many critical applications. Some uses include manufacturing applications, precision alignment and precision fluid metering to name a few.

Linear actuators that use a screw would also have its precision be dependent of the thread pitch. Inside the rotor of a linear actuator, a nut is located in the center of the rotor. Also, a corresponding screw is engaged in the nut. In order for the screw to move axially, the screw must be constrained from rotating with the nut and rotor assembly by some means. With anti-rotation of the screw, linear motion is achieved as the rotor turns. Anti-rotation is typically accomplished either internally with captivation of a shaft screw assembly or externally with a nut on the screw shaft that is some way prevented from rotation, yet free along its axis.

For obvious design simplicity, it makes sense to accomplish the rotary to linear conversion right inside the motor. This approach greatly simplifies the design of many applications by allowing a “drop in motor” capable of precise linear motion without the need to install external mechanical linkages.
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