Roundness error separation based on singularity detection and exact-stop of spindle in on-machine measurement of spindle rotation error

Abstract

At present, non-contact sensors are being extensively used for the measurement of spindle rotation errors. However, as the measuring target of the sensors, the roundness error of the artifact inevitably mixes into the error motion of the spindle. Moreover, the challenging nature of manufacturing high-precision artifacts has resulted in the separation of the roundness error of artifacts from the spindle rotation error being considered an urgent research prospect. In this study, a roundness error separation method based on singularity detection and exact-stop of spindle was proposed to perform on-machine measurement of spindle rotation error, wherein compared to the existing methods, the proposed method implements the Donaldson reversal method. It is independent of the index signal of the spindle encoder, which is usually unavailable on actual machine tools. The singularity of measured motion was detected using the wavelet transform modulus maximum (WTMM) ridges and their Lipschitz exponents, to locate the exact-stop and rotating stages of spindle in the measured motion. Consequently, a WTMM ridge extraction method was established to extract the continuous optimal WTMM ridges of the measured motion. Further, the synchronous motion of the measured motion was used for roundness error separation to promote the separation accuracy. Finally, the effectiveness of the proposed method was verified using the measurement results of a coordinate measuring machine (CMM). Thus, the measurement error caused by the roundness error of the artifact can be reduced significantly by applying the proposed method to the on-machine measurement of the spindle error motion.