Determination of optimal Prestretching of Ball Screw

Abstract

The prestretching of ball screw can effectively increase the positioning accuracy, but high value of prestretching can lead to the bearing excessive heat and affects its life, thus the research of optimal prestretching has important significance. Optimal prestretching of ball screw which influenced by the axial load and temperature increase which is related to the axial load, need meet the requirement of the ball screw to be in the state of tension under the maximum axial load. The deformation of ball screw under the axial load is named as load deformation and the deformation due to the thermal is named as thermal deformation. The optimal prestretching is used to compensate the maximum load deformation(MLD) and the maximum thermal deformation (MTD). In order to insure the axial stiffness of the ball screw to be stable, the axial load of ball screws is not more than three times the preload. So the three times preload of ball screw is as the maximum axial load. The optimal prestretching is the sum of the MLD and MTD. The temperature distribution and thermal deformation has been obtained when the ball screw reach thermal equilibrium. Combined with thermal-mechanical coupling analysis, the optimal prestretching has been obtained for the different axial load and different preload. The analysis results show that the MTD plays a main role influencing the optimal prestretching, and the MLD occupies the optimal prestretching maximum to 10.61%.