Monday, July 9, 2018

Different ways of stepper motors going into linear actuators

Stepper motors that are traditional rotary motors couple to mechanical rotary-to-linear motion devices (often in the form of a threaded shaft that mates with traversing nut or carriage) to produce linear motion. In this actuator setup, the motor output shaft usually couples to the screw to turn it … and advance the nut (or carriage) and attached load. These are usually small designs that go into consumer products or small-stroke applications in industrial machines.

In contrast, true linear stepper motors—which this FAQ covers in more depth—function much like linear-motor types but leverage the same mode of operation as rotary stepper motors to produce linear motion. More specifically, traditional linear-stepper motors (using variable-reluctance operation) have a moving carriage called a forcer with a permanent magnet, laminated steel cores (which the manufacturer cuts into teeth) and coils around the laminated cores. This forcer engages a straight and stationary track called a platen. This linear-stepper part is mostly steel bar cores (which the manufacturer cuts into teeth and plates with nickel). For super-long strokes, installers can put multiple platens end-to-end and have the forcer ride on all of them.

Summary of linear stepper motors
Engineers most commonly use these linear actuators in larger installations; on axes that move heavier loads; and in high-end medical or material-handling applications such as pick-and-place machinery that require extremely high precision. Like rotary equivalents, linear stepper motors or precision linear actuator either use a variable reluctance (just described) or a hybrid mode of operation. A hybrid linear-stepper platen is like that of a variable-reluctance linear stepper. In contrast, the forcer has multiple permanent magnets, magnetic U-shaped cores (with coils around them) and a steel yoke.

True Linear Stepper Motor

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