In most applications, preload is applied to double-nut ball screws to improve the positioning accuracy and rigidity. However, the applied preload degrades owing to wear, which lowers the positioning accuracy of the ball screws, and thus affects the accuracy of computer numerical control machine tools. In this study, to obtain the dynamic contact force and sliding velocities on the ball-raceway contact, we established a load distribution model and velocity variation model, respectively. Based on these models, we propose an accurate model for predicting the preload degradation of double-nut ball screws. The degraded preload of three ball screws was measured under high axial load-low speed, medium axial load-medium speed, and low axial load-high speed, with a running stroke of 7.2 million revolutions. The experimental results are in good agreement with the theoretical values calculated by the prediction model, which confirms the validity of the prediction model. Therefore, it was concluded that the proposed preload degradation model can accurately predict the performance and service life of double-nut ball screws.

在大多数应用中，预紧力施加在双螺母滚珠丝杠上，以提高定位精度和刚度。然而，所施加的预载荷由于磨损而劣化，这降低了滚珠丝杠的定位精度，从而影响了计算机数控机床的精度。在这项研究中，为了获得在球-滚道接触上的动态接触力和滑动速度，我们分别建立了载荷分布模型和速度变化模型。基于这些模型，我们提出了一个精确的模型来预测双螺母滚珠丝杠的预紧力下降。在高轴向负荷-低速，中等轴向负荷-中速和低轴向负荷-高速下，以720万转的运行冲程测量了三个滚珠丝杠的退化预紧力。实验结果与预测模型计算出的理论值吻合良好，证实了预测模型的有效性。因此，可以得出结论，所提出的预紧力退化模型可以准确地预测双螺母滚珠丝杠的性能和使用寿命。