Measurement and evaluation of cylindricity deviation in Cartesian coordinates

In the earlier studies of the Liu et al (2015 Intersecting chord method for minimum zone evaluation of roundness deviation using Cartesian coordinate data Precis. Eng. 42 242–52, 2016 Minimum circumscribed circle and maximum inscribed circle of roundness deviation evaluation with intersecting chord method IEEE Trans. Instrum. Meas. 65 2787–96), the intersecting chords method was proposed for modeling roundness and sphericity deviations. Because cylindricity deviation is partially associated with both deviations, this study focuses on the measurement and evaluation of cylindricity deviations using the intersecting chords method in the Cartesian coordinate system. Combined with the geometric structure of a cylinder, the measurement method of the cylindricity deviation in Cartesian coordinates is introduced, and the cylindricity measurement is conducted by multi-section sampling, axis fitting, and spatial projection. Based on this, the intersecting chords method is employed to construct models for the cylindricity deviation evaluation using the point coordinates obtained from the cylindricity measurements, including minimum circumscribed cylindricity, maximum inscribed cylindricity, and minimum zone cylindricity. The core of the intersecting chords method is using a chord instead of a curve as the characteristic element of the evaluation model. Moreover, the cross structure produced by the intersecting chords can control the position of the reference form and obtain the center of the evaluation model accurately. For the cylindricity deviation, the intersecting chords method not only reduces the modeling difficulty but also improves the evaluation accuracy. Moreover, the availability and validity of the modeling method are further verified by the experimental data obtained from coordinate measuring machines, and the results show that the research study is useful for developing measurement instruments and manufacturing equipment having large cylindrical parts. (paper)