A novel invariant-based methodology for accuracy characteristics of motorized spindles

Rotational accuracy is a critical performance indicator for motorized spindles. However, conventional evaluation methods are constrained by the installation position of reference components, resulting in inconsistent accuracy characterization metrics. To address this limitation, this study proposes a novel evaluation model for characterizing spindle rotational accuracy. By introducing the invariant theorem of axis system rotational accuracy, a unified evaluation metric is established that reduces the measurement deviations caused by reference component positioning variations by over 5%. The proposed method investigates the influence of rotational speed on spindle rotational accuracy, the radius of the fitted minimum directrix circle, which serves as an evaluation metric for radial accuracy, measures 0.39 μm at 500 rpm and 3.81 μm at 14,000 rpm. The study also analyzes the effects of temperature on rotational accuracy and thermal elongation. These analyses establish a theoretical foundation for the performance evaluation of motorized spindles.