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A leadscrew (or lead screw), also known as a power screw [1] or translation screw, [2] is a screw used as a linkage in a machine, to translate turning motion into linear motion. Because of the large area of sliding contact between their male and female members, screw threads have larger frictional energy losses compared to other linkages.
A traveling-screw linear actuator has a lead screw that passes entirely through the motor. In a traveling-screw linear actuator, the motor "crawls" up and down a lead screw that is restrained from spinning. The only spinning parts are inside the motor, and may not be visible from the outside. Some lead screws have multiple "starts".
An electromechanical actuator (EMA) uses mechanical means to convert the rotational force of an ordinary (rotary) electric motor into a linear movement. The mechanism may be a toothed belt or a screw (either a ball or a lead screw or planetary roller screw).
A typical ball screw may be 90 percent efficient, versus 20 to 25 percent efficiency of an Acme lead screw of equal size. Lack of sliding friction between the nut and screw lends itself to extended lifespan of the screw assembly (especially in no-backlash systems), reducing downtime for maintenance and parts replacement, while also decreasing ...
Screws are also used as linkages in machines to transfer power, in the worm gear, lead screw, ball screw, and roller screw. Due to their low efficiency, screw linkages are seldom used to carry high power, but are more often employed in low power, intermittent uses such as positioning actuators .
Planetary roller screws are used as the actuating mechanism in many electromechanical linear actuators. Due to its complexity, the roller screw is a relatively expensive actuator (as much as an order of magnitude more expensive than ball screws), but may be suitable for high-precision, high-speed, heavy-load, long-life, and heavy-use applications.
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