Ball Screw Assemblies

It is immediately apparent that a ball screw cannot be described as a simple tool. Actually there are a lot of pieces with the whole thing being called a ball screw assembly. The central parts of a ball screw assembly are the pieces called the nut and the screw. The nut moves linearly on the screw when either of these two parts are rotating. Most commonly the circular movement of the screw causes the nut to move sidewards, but the action can also be reversed which means the ball screw is being back-driven. Ball screw assemblies aren’t really exceptionally intricate. The nut contains ball bearings, and these circulate through the ball nut. The appearance of the screw is typical, in that it has helical threads cut into it. Within the nut similar threads have been created which create tracks for the ball bearings to follow. Once the screw revolves this sets the ball bearings into motion, which is the cause of the nut’s movement on the screw. The ball screw assembly has a deflector as a last component that keeps the ball bearings in circulation inside the nut. Once the ball moves to the end of the nut the deflector reverses its motion, sending it back to the top of the nut. A circuit is therefore formed, or a cycle of ball bearings inside the nut casing. This is the fundamental mechanism of the ball screw assembly.

It is possible to work out the life and load of ball screw assemblies by counting the threads on the screw along with the amount of threads inside the nut. For every instance that equates to a complete movement of the nut along the screw, every screw thread has had each ball bearing travel along it once. As well as this, the threads in the barrel of the nut may have had the balls pass through them many times over which of course is dependent on the relative screw length. It can be seen that the proportional difference between the nut thread count and the screw thread count will reveal the amount of extra work done on the ball nut surface which should help you to work out how long the ball nut will last when compared with the life of the ball screw. Some ball screw assemblies can be expected to have a greater durability, as can be calculated using the relative thread counts.