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The raceway profile greatly influences the performance of a ball screw. Although the traditional circular raceway profile is simple in structure, it can be a limitation to the load carrying capacity of ball screws. In this paper, a novel type of ball screw raceway profile is proposed based on geometrical close contact theory. Firstly, the second-order approximation curve of the ball is derived using the McLaughlin formula in the normal plane of the raceway helix, which serves as the basis for constructing the close raceway profile. The mathematical expression of the contact stress distribution of the close raceway is then obtained using Chebyshev polynomials. A comparison and analysis of the contact stress distribution between the close raceway and the conventional raceway is carried out. Furthermore, simulation models of ball screws with the close raceway profile are established and the contact behavior of the ball with both types of raceways is statically simulated using ANSYS software. The dynamic performance of both ball screws is compared and analyzed using ADAMS software. The analysis results show that compared with the conventional raceway ball screw, the close raceway ball screw has lower stress, strain, and friction torque under the same load conditions. These research results have significant implications for the structural optimization of ball screws. [ABSTRACT FROM AUTHOR]

The ball screw (BS) has become an indispensable key functional component in many fields, such as precision manufacturing equipment and intelligent manufacturing production lines. Inevitable geometric errors and non-constant operating conditions affect the accuracy decay of the BS component. In this paper, a numerical analysis method of this accuracy decay with geometric parameters errors, under non-constant operating conditions, is established. The accuracy degradation of the BS, under a single non-constant operation condition or multiple non-constant operating conditions, is analyzed, using a proposed numerical analysis method. The average value of the relative error between numerical analysis and theoretical model results was 5.52%, 5.66%, and 5.40%, under the three operating conditions of non-constant rotation rate (RR), non-constant contact load (CL), and non-constant rotation rate and contact load (RR + CL), respectively. And the maximum relative error value was 11.11%, 11.11%, and 10.98%. In addition, the numerical analysis method of BS accuracy degradation was compared to experimental tests. The average value of the relative error between numerical analysis outcome and experimental tests was 7.07%, 6.08%, 6.56%, and the maximum relative error value was 11.11%, 14.29%, and 13.04% under the three operating conditions of RR, CL, and RR + CL, respectively. [ABSTRACT FROM AUTHOR]

The accurate model of the load state for all balls under multidirectional load is very helpful for the design process of ball screws. The contact deformation model of the ball screw without consideration of the stress difference of all balls is inaccurate. In this paper, a novel contact load model of the ball screw is established by considering coupled axial, radial load to study the elastic deformation displacement and position accuracy. The deviation and variation of axial elastic deformation with the dimension errors of all balls are investigated to obtain the influence of load state on the precision sustainability of the ball screw. The position precision including travel deviation and variation by considering load distribution of all balls is studied under the different load conditions. In addition, a new working bench is designed to study the position precision of the ball screw. The experimental study is carried out to obtain the relationship between the position precision and the contact load state of all balls, which is a reference to compensate for the precision loss of the ball screw. [ABSTRACT FROM AUTHOR]

Ball screws are the driving components used to convert the rotational motion into linear motion in precision equipment. However, the machining accuracy of precision equipment is directly determined by the positioning accuracy of the ball screw. The authors analyze the precision sustainability of preload double-nut ball screws with raceway wear. A new wear model combining the modified Archard theory and the iterative interpolation method is established to analyze the variations in wear depth. A new model considering the coupling relationship between raceway wear and preload loss is proposed to study the precision life of the double-nut ball screw. In addition, a novel running test bench is designed to verify the precision sustainability of ball screws. The precision sustainability of the ball screw is analyzed during its life cycle, and these results match the theoretical values obtained by using the wear model. [ABSTRACT FROM AUTHOR]

• 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. 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. [ABSTRACT FROM AUTHOR]

Precision double-nut ball screws are key functional parts in machine tools. The positioning accuracy of a ball screw can directly affect the machining accuracy of a machine tools. During actual use, the preload degradation and the large axial clearance of the double-nut ball screw are caused by the contact wear, which directly affects the transmission positioning accuracy. The contact wear is focused on the ball and the rough raceway surface of the ball screw. Therefore, a novel method is proposed in this paper to characterize the rough spherical morphology of raceways for ball screws based on fractal theory, and the fractal parameters of the screw and nut raceways are identified. A fractal contact model of the asperity on the raceway surface is established. By introducing contact parameters to modify the contact area, an area distribution function suitable for the coordinated contact is obtained. A mathematical model for calculating the normal contact load of the ball screw in three states is established by considering the friction factor. A precision loss model of the ball screw is established based on the full ball load distribution model and the multiscale contact load model, and the proposed model is verified by experiments. The surface contact coefficient of the inner and outer raceways is discussed. The influence of raceway fractal parameters on the wear rate is analyzed, and coupling research on precision loss and preload degradation for the ball screw is carried out. The initial wear rate under different axial load is discussed, and the change trend of wear rate with time is analyzed. The precision loss model of the preload double-nut ball screw based on fractal theory provides a new theoretical basis for accurately predicting the precision degradation and provides method support for establishing the wear life prediction of a ball screw. • Raceway wear considering surface fractal can lead to precision loss of ball screw. • Wear volume of the work nut is different from the preload nut under axial load. • Preload of ball screw degenerates with the increasing contact wear of raceways. • Time-varying wear rate affected by operating parameters is coupled to preload loss. [ABSTRACT FROM AUTHOR]