As you may know a ball screw is not a straightforward one-piece tool. In fact there are a number of components and all of the pieces together are called a ball screw assembly. The two main components of a ball screw assembly are the screw and the nut. The nut travels down the screw regardless of which of the two parts is moving. In general the circular movement of the screw is transferred to the nut, which moves in a straight line, but the action may be swapped so that the ball screw is back-driven.
Ball screw assemblies cannot be seen as being extremely complicated. There are ball bearings inside the nut, which are free to move within the assembly. The screw is much like any other screw, with threads along its length. In the nut’s interior there are also matching grooves which direct the motion of the balls. Once the screw revolves this causes the ball bearings to move, which makes the nut travel along the screw. The ball screw assembly features a deflector at its base which pushes the ball bearings back to the top of the nut. As soon as a ball gets to the base of the nut the deflector reverses its motion, sending it back to the top of the nut. A circuit is therefore formed, with a continuous circulation of ball bearings contained behing the casing of the nut. This is the core of the ball screw assembly.
You can estimate the lifespans of ball screw assemblies by counting the threads on the screw in conjunction with the number of threads in the barrel of the ball nut. On each occasion that a full journey along the screw has been completed, each section of screw thread has been run over by every single ball bearing once. But also, the nut’s threads may have had the balls pass through them many times over depending on the length of the screw. In this way the difference between the nut thread number and the screw thread number will reveal the additional wear on the interior threads of the nut and will therefore give you an indication of how quickly the ball nut will wear out against the lifespan of the ball screw. Different ball screw assemblies will have greater lifespans than others, as indicated by the appropriate numbers.
Ball screw assemblies cannot be seen as being extremely complicated. There are ball bearings inside the nut, which are free to move within the assembly. The screw is much like any other screw, with threads along its length. In the nut’s interior there are also matching grooves which direct the motion of the balls. Once the screw revolves this causes the ball bearings to move, which makes the nut travel along the screw. The ball screw assembly features a deflector at its base which pushes the ball bearings back to the top of the nut. As soon as a ball gets to the base of the nut the deflector reverses its motion, sending it back to the top of the nut. A circuit is therefore formed, with a continuous circulation of ball bearings contained behing the casing of the nut. This is the core of the ball screw assembly.
You can estimate the lifespans of ball screw assemblies by counting the threads on the screw in conjunction with the number of threads in the barrel of the ball nut. On each occasion that a full journey along the screw has been completed, each section of screw thread has been run over by every single ball bearing once. But also, the nut’s threads may have had the balls pass through them many times over depending on the length of the screw. In this way the difference between the nut thread number and the screw thread number will reveal the additional wear on the interior threads of the nut and will therefore give you an indication of how quickly the ball nut will wear out against the lifespan of the ball screw. Different ball screw assemblies will have greater lifespans than others, as indicated by the appropriate numbers.
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