Steinmeyer uses all commonly known designs for ball returns. However, the multi-liner and the tube return are only used for aerospace "build-to-print" applications, since staying with a previously qualified design simplifies the qualification procedure.
Track-to-track (internal return)
The track-to-track return uses ball deflectors to lift the balls across the O.D. of the shaft and guide them directly into the next (or previous) track. Internal ball return is very compact and yields the smallest nut diameters among all ball return systems. It is also the ball return of choice for very small ball sizes and small leads.
Each deflector serves one turn, which is one circuit (or ball circle).
Through-the-nut return (external return)
Steinmeyer's "UltraSpeed" return is normally used for lead/diameter ratios greater than 0.5. It is normally used with dual start threads. Balls are lifted off the shaft using a deflector at one end of the nut and then guided through a bore (internal to the nut body) to the other end of the nut, where a similar piece guides the balls back onto the thread. One pair of deflectors serves one circuit (i.e. one of the threads) which includes several turns.
End cap return
End cap return works very much like the previously described through-the-nut return, with the exception that the ball deflector function is executed using a (plastic) cap at both ends of the ball nut. Each cap serves as the ball return and also includes wipers. End cap return is normallly used for very large lead/diameter ratios. This style ball nut is only available as a flange nut.
Ball nuts require a means to recirculate balls. Without it, the ball path would not be closed and balls would fall out at the rear end of the nut.
Design of the ball return is the determining factor for the maximum speed at which the ball nut can safely operate. This is normally expressed by the DN-value. The better the ball return system deals with mass forces of the balls, the higher the DN value. Manufacturers typically quote DN values from 60,000 for basic tube returns to 160,000 and higher, e.g. the UltraSpeed return from Steinmeyer.