A ball screw (or ballscrew) is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads, they can do so with minimum internal friction. They are made to close tolerances and are therefore suitable for use in situations in which high precision is necessary. The ball assembly acts as the nut while the threaded shaft is the screw. In contrast to conventional leadscrews, ballscrews tend to be rather bulky, due to the need to have a mechanism to recirculate the balls.
Another form of linear actuator based on a rotating rod is the threadless ballscrew, a.k.a. "rolling ring drive". In this design, three (or more) rolling-ring bearings are arranged symmetrically in a housing surrounding a smooth (threadless) actuator rod or shaft. The bearings are set at an angle to the rod, and this angle determines the direction and rate of linear motion per revolution of the rod. An advantage of this design over the conventional ballscrew or leadscrew is the practical elimination of backlash and loading caused by preload nuts.
Keywords
use
nuts
need
rate
form
angle
three
design
loading
housing
contrast
backlash
direction
mechanism
advantage
situations
ball screw
revolution
ballscrews
tolerances
rotating rod
ball bearings
linear motion
ball assembly
threaded shaft
high precision
precision screw
helical raceway
little friction
rotational motion
high thrust loads
rolling ring drive
threadless ballscrew
practical elimination
conventional ballscrew
conventional leadscrews
minimum internal friction
mechanical linear actuator
smooth (threadless) actuator rod
