Ball Screw
A ball screw is an ingenious device that can translate rotational motion into linear motion. This happens without much friction, so only a small amount of energy is wasted. It also means that the mechanism within the ball screw becomes worn very gradually. A ball screw is usually larger than a leadscrew, because it has parts in the interior of the ball screw nut. Inside a ball screw mechanism there is some solid metal ball bearings which roll through the threaded interior of the barrel.
It is very important that no dirt or other obstructions find their way inside the ball screw nut casing. The metal balls inside the mechanism need complete freedom of motion along the grooves and any tiny speck of dust can block this. Ball screws are known to have long lifespans, and known to be very accurate. Clearly these advantages will be hindered if dirt enters the barrel. To prevent this the factory craftsmen always avail of bellows and other methods so as to make certain that no tiny dirt specks becoming lodged inside the ball screw nut.
Ball screws are known to be highly accurate as a result of the manufacturing process. It is for this reason that they are incorporated in machines that depend on almost perfect precision, such as in robots, aircraft and missiles. Another application of these tools is in steppers, which are used to make semiconductors.
In some cases ball screws can be back-driven. In other words instead of inputting rotational motion and obtaining a linear movement as an output, the user can also start out with a straight line movement and generate turning forces. This option is available as a result of the low friction in the interior of the apparatus, which literally means that the components will not jam.