Ball bearings are critical components of all types of ball screw assembly. They are located within the ball screw nut, kept within the casing. Some forms of ball screw feature the ball bearings encased within a custom cage, while other designs utilize the shell of the ball φ15-φ500 Extruder Screw Barrel screw nut itself to contain the ball bearings.Common ball screw assemblies usually have a good amount of ball bearings, located along the threads in the ball screw nut, and with the threads of the screw itself. As the screw turns, this causes the ball bearings to roll down the screw.

 This also forces the ball screw nut further down the screw, because the rolling of the ball bearings causes the ball screw nut into motion. This is how the ball screw assembly operates as a linear actuator. It uses the screw’s rotation and causes the ball screw nut to move linearly.In all ball screw assemblies, every ball bearing will start off at one end of the ball screw nut and then move along the grooves to the base of the nut. Then the ball bearings will have to be returned to the upper part of the ball screw nut to continue the cycle. 

The typical ball screw assembly has to contain a recirculation apparatus that pushes each ball bearing in a constant cycle. Different recirculation apparatuses can be incorporated, which depend on the variation of ball screw under consideration. Most ball screw assemblies feature wipers to help stop particles of dust and dirt from gaining entry to the ball screw. Objects of this kind can block the free motion of the ball bearings. Small amounts of oil or grease are commonly used to seal the mechanism, and to further free up the motion of the ball bearings.

 When a ball bearing reaches the bottom of the nut, the end cap collects it and it is redirected into a hole that has been pierced at an angle across the ball screw nut. It then falls into the other cap, which places it back into the raceway.The external ball nut follows a similar idea, which recirculates the ball bearings using a separate tube.

 In order to redirect the balls into the tube a small pick up finger is included, and the ball bearings then roll along the tube back to the upper end of the ball screw nut, where they are then returned to the raceway. Finally, another common design of recirculation system in ball screw assemblies is called the internal button ball nut. This type of recirculation system uses a machined button which includes a separate thread along which the ball bearings move to return to the top of the ball screw nut.