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A ball screw (BS) is a key functional component for precision machining equipment, medical instruments, and intelligent manufacturing production lines. The accuracy reliability of a ball screw plays a key role in the functioning of all such equipment. Since the operating conditions have time-dependent characteristics, the non-constant operating conditions affect the BS accuracy decay. In this paper, the numerical modeling and analysis of the BS accuracy decay are considered under non-constant operating conditions. The BS accuracy reliability under single and multiple non-constant operating conditions is investigated. The experimental findings on accuracy decay under non-constant operating conditions validate the proposed analysis. The average relative error of accuracy decay between the theoretical and the experimental findings is estimated at 10% (in the range of 10.15%–12.66%). The error is evaluated under the three different amplitudes operating conditions, including AL (non-constant axial load), FR (non-constant feed rate), and AL plus FR. The results show that the accuracy decay prediction model successfully predicts the BS accuracy reliability under non-constant operating conditions. [ABSTRACT FROM AUTHOR]

The combination of sliding/rolling motion can influence the degree of precision degradation of ball screw. Precision degradation modeling and factors analysis can reveal the evolution law of ball screw precision. This paper presents a precision degradation model for factors analysis influencing precision due to mixed sliding-rolling motion. The precision loss model was verified through the comparison of theoretical models and experimental tests. The precision degradation due to rolling motion between the ball and raceway accounted for 29.09% of the screw precision loss due to sliding motion. Additionally, the total precision degradation due to rolling motion accounted for 21.03% of the total sliding precision loss of the screw and nut, and 17.38% of the overall ball screw precision loss under mixed sliding-rolling motion. In addition, the effects of operating conditions and structural parameters on precision loss were analyzed. The sensitivity coefficients of factors influencing were used to quantitatively describe impact degree on precision degradation. [ABSTRACT FROM AUTHOR]

At present, wear models and accuracy prediction of guideway are established based on elastoplastic mechanics of continuous media. These methods are limited to describe the process of accuracy degradation by using the material performance defined based on macroscopic hypothesis condition. In this paper, the multiscale method based on quasicontinuum medium(QM) principle is proposed to describe the degradation process of guideway linear precision with an exponential model. According to the wear distribution of the guideway surface with the micro-morphology evolution process, the measurement value of the guideway linear precision is modeled systematically. Then, using the quasicontinuum medium method instead of the continuum hypothesis, the exponential wear model of guideway is established. The exponential wear model uses the wear exponent to describe the wear status based on linear precision measurement rather than tremendous wear volume tests. By means of Depth From Defocus (DFD) method, the micro-topography information of the guideway surface is obtained. Therefore, the wear state of the guideway is verified under different loading conditions, and the validity of using the QM method to establish the guideway exponential wear model is verified. [ABSTRACT FROM AUTHOR]

Ball screw mechanisms (BSMs) are used as accuracy transmission components in a wide range of industries and are characterized by their high accuracy. More specifically, the positioning accuracy of BSM has a significant effect on the accuracy of machine tool. Based on the macro-micro multiscale method, an exponential prediction model for the BSM positioning accuracy was developed considering time-varying working conditions (load and rotational speed) and feed modes. Since the accuracy degradation is mainly caused by wear, a microscopic approach was proposed to describe the positioning accuracy retention and the microscopic wear process was investigated. The sliding contact of the asperities between the ball and raceway was analyzed, and the microscopic wear behavior of the asperities was determined. Considering the time-varying working conditions, the BSM positioning accuracy characteristics were obtained under the normal feed mode by conducting suitable tests. The exponential wear model used the wear index to describe the wear status based on the positioning accuracy measurement. The accuracy loss value and the prediction index of positioning accuracy were determined based on an exponential model, and the effective lifetime of the BSM was predicted. Finally, the exponential prediction model was used in negative/positive skew feed distribution, and the effective lifetime determined. [ABSTRACT FROM AUTHOR]