If there is axial clearance in the ball screw nut pair and there is elastic deformation at the contact between the ball and the raceway under load, then when the screw rotates in the opposite direction, a backlash error will occur. In order to eliminate the backlash error, two nuts 1 and 2 are assembled on the screw, and the axial position of the two nuts is adjusted so that the balls in the two nuts are pressed against the opposite side of the screw thread raceway with a certain pressure before bearing the load, causing them to deform to a certain extent (as shown in the figure), thereby eliminating axial clearance and improving axial stiffness. There are three commonly used methods for adjusting pre tightening.
Adjustment preloading method for eliminating axial clearance with ball screw
1. Gasket clearance adjustment method: As shown in the figure below, by adjusting the thickness of gasket 2, nut 1 can move axially to eliminate axial clearance and pre tighten. This method has a simple structure, high reliability, and good rigidity. In order to avoid disassembling the nut during adjustment, the gasket can be made into a split shape. The disadvantage is that precise adjustment is difficult, and when the raceway wears out, it cannot be adjusted arbitrarily unless the gasket is replaced. Therefore, it is suitable for general precision transmission mechanisms.
2. Thread clearance adjustment: As shown in the figure, the outer end of nut 1 has a protruding edge, and the threaded outer end of nut 3 extends out of the nut seat and is locked with two round nuts 2. Rotate the round nut to adjust the axial clearance and preload. The characteristics of this method are compact structure, reliable operation, and easy adjustment. The disadvantage is that it is not very precise. The marking of 4 is to prevent relative rotation of the two nuts.
3. Tooth difference adjustment type: As shown in the figure, cut an external gear (z2=z1+1) with one tooth difference on the flange of nuts 1 and 2, and install it into the nut seat to mesh with internal gears 3 and 4 with corresponding tooth numbers (z1 and z2). When adjusting, first remove the internal gear, rotate the two nuts in the same direction relative to the nut seat by a certain number of teeth, and then fix the internal gear. At this point, there is a corresponding axial displacement between the two nuts, thus achieving the purpose of adjustment. Welcome to consult and purchase TBI ball screws from all walks of life. Shenzhen Jieyuan Electromechanical Equipment looks forward to your call.
