Investigation of load distribution and deformations for ball screws with the effects of turning torque and geometric errors. (November 2019) - Zhao, Jiajia
Highlights: Standard load distribution of ball screw to which turning torque is applied is a periodic shape of increasing amplitude. Contact loads of all balls with geometric errors are bounce around the standard load distribution shape. Axial deformation of ball screw will change constantly with all balls running in the raceway. Variation of axial displacement caused by deformations can lead to uncertainty in transmission accuracy of ball screw. Fatigue life of ball screw considering uneven load distribution is shorter compared to the uniform load distribution. Abstract: Ball screws are the driving component used to convert rotational motion to linear motion for precision equipment and may be applied with the turning torque in practice. In past research, the contact load between ball and the raceway is assumed to be uniform wherein only the axial load is considered. This paper aims to establish a load distribution model to analyze the contact load of all balls when a turning torque caused by assembly error is applied. The axial dynamic deformation model is obtained to study the effect of the elastic creep on transmission accuracy. The authors use the kinematic analysis method to obtain the load distribution and axial elastic deformation considering the geometric errors of balls. The relationship between the introduced deformation coefficient and the defined geometric error coefficient are analyzed, and the change trend of the maximum deformation coefficient varying with geometric error coefficient is obtained. Furthermore, the position deviation and position precision of the ball screw are studied, and the fatigue life of the ball screw is analyzed based on the maximum contact load. The results show that the load distribution model considering geometric errors with the effect of turning torque proposed in this paper is a satisfactory reference to study the precision sustainability of ball screw.