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What Is a Ball Screw Actuator?

Paul Scott
Paul Scott

A ball screw actuator is a device that supplies a linear, high-thrust load movement used to activate other equipment using a precision machined lead screw and ball bearings. The actuators output motion is achieved by placing several rows of helically-arranged, captive ball bearings within a sleeve which acts as a motion transfer agent. The rows of balls are arranged in such a fashion as to correspond to the pitch of the lead screw threads as it passes through the nut. The balls thus lie in the threads of the lead screw, and, as it rotates, cause the nut to move up or down its length. The nut is, in turn, attached to an actuator arm, which serves to transfer the nuts movement to the activated device.

Actuators are remote devices used to produce work by converting a source of power, typically electric current or compressed gas and oil, to a linear or rotary movement. The output movement is then harnessed to switch, move, or activate a secondary device where it is impractical or dangerous for an operator to do so. The ball screw actuator is one such device that produces a linear, or straight-line, output motion from a rotary input. The input energy is typically supplied by an electric motor and is translated to a linear output using an accurately machined lead screw and a set of captive ball bearings.

Woman holding a book
Woman holding a book

The ball bearings used in the ball screw actuator are housed within accurately machined grooves in a metal or composite sleeve. The lead screw passes through the sleeve with one end supported by a bush or bearing, and the other attached to the drive shaft of the motor. The balls within the sleeve are arranged to correspond to the exact pitch and spacing of the lead screw threads, and are positioned to lie snugly within those threads. When the motor turns the lead screw, the balls act as rotating nut threads, allowing the sleeve to move up and down the length of the lead screw with minimal friction. The sleeve is attached to the actuator output arm of the device, which transfers its motion to the mechanism requiring activation.

The precision, low-friction movement of the ball screw actuator mechanism allows the device to produce very high levels or actuation torque with very little strain on its working parts. The mechanism's inherent precision also produces very high levels of accuracy in the actuator's output. These characteristics make the ball screw actuator an ideal option for precise, high-load actuation applications.

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