The characteristics of two kinds of circulating ways of ball screw

Two kinds of common circulating ways of ball screw: outer loop and inner loop.

What is the outer loop? Balls in the loop process accidentally disengagement with the screw called outer loop; what is the inner loop? Always keep in contact with the screw called the inner loop. Each cycle of the ball is called a column, and the number of the lead in each ball cycle is called laps. Inner loop ball screw each nut have two, three, four, five columns and so on, each column only one lap; the outer loop each column has 1.5 laps, 2.5 laps and 3.5 laps, and so on.

1, Outer loop

Outer loop is a ball at the end of the cycle through the nut outer surface of the spiral groove or intubation tube returns to screw nuts and re-enter circulation. Outer loop ball screw nut according to ball circulation return ways mainly have cover type, intubation tube type and spiral groove type. Outer loop ball screw outer loop structure and manufacturing process complexity, the disadvantage is difficult to do raceway seams smooth, affect the smoothness of the ball raceway.

Cover type, processing a longitudinal bore in the nut, as the ball return passage, opened the backhaul mouth at both ends of the ball nut cover, the ball from this enter the return pipe, forming a loop.

Intubation tube type, it use elbow as a return pipe, this structure technology is good, but because the pipe protruding from the nut body, the radial size is larger.

Spiral groove type, it is outside the nut circular milling spiral groove, through holes drilled at both ends of the groove and the thread roller tangent to form a return passage, this structure is smaller than the radial size of the intubation structure but manufacturing is more complex.

2, Inner loop

Inner loop ball screw. Inner loop are using the inverter to achieve ball circulation, there are two types of inverter.

Cylindrical convex key inverter, its cylindrical portion embedded in the nut, the end has opened a reverse groove, reverse groove is positioned by a cylindrical outer surface and the upper end of round keys to ensure the alignment thread rolling direction.

Oblate insert inverter, the inverter is generally round flat key inserts, inserts embedded nut grooving, its end opened reverse groove, positioning with the outer contour of the insert. Two inverter comparison, the smaller the size of the latter, thereby reducing the radial dimension of nut and shorten the axial dimension. But the higher requirements of the outer contour of this inverter and nut grooving dimensional accuracy.

Source: http://www.machineballscrew.com Ball Screw Assemblies