Ball Screw Assembly Recirculation Systems

A ball screw assembly contains a number of parts, which includes the screw, ball screw nut and ball bearings. Other components are sometimes added, such as cages and wipers. The recirculation system is arguably the component that is most critical to the ball screw.
This part of the ball screw apparatus is essential, as it is this apparatus that moves the ball bearings from the bottom of the ball screw nut back to the top. This is clearly the part of the assembly that creates the cycle that the ball bearings must follow, permitting the ball screw nut to exhibit linear motion along the screw shaft.

There are a variety of recirculation designs in use today. For example one option is the end cap return ball nut, which makes use of a small cap added to the base of the ball screw nut. Another cap of the same size and design is also attached to the upper part of the ball screw nut. The moment a ball bearing rolls out of the ball screw nut’s end, the end cap collects it and it is pushed into a hole which cuts diagonally along the ball screw nut. Once through the hole it is collected by the top cap, which pushes it back onto the threads of the ball screw nut.
Another common recirculation system is known as the external ball nut, which has a special tube to return the ball bearings to the top of the nut. The ball bearings are steered into the entrance of the tube by a special pick up finger, and the balls are recirculated to the upper end of the ball screw nut by moving along the tube, where they start to roll along the interior threads again.
Another method of recirculating that is commonly employed in ball screw assemblies has the title of the internal button ball nut. This apparatus has a machined button which features its own threadway that moves the ball bearings from the base of the ball screw nut to the top.