Like linear feed axes, rotary tables have six types of systematic error. These errors are mainly caused by the inaccuracy of the manufacturing and assembly process of the rotary table, which results in a disturbing movement superposed on the theoretical rotation. The six systematic errors of rotary tables can be divided into two groups, the first being the translational error, i.e. two eccentricity errors along the local x- and y-axis, and the axial runout along the local z-axis (rotating axis), and the second being three angular errors, i.e. two wobble errors about the local x- and y-axis, and the angular error about the local z-axis. This paper presents a calibration device capable of measuring all six systematic errors of rotary tables simultaneously in a single continuous measurement according to ISO 230[l, 2]. The measuring device is based on an angle encoder with a waffle-type grating placed on a cylindrical surface. Using six scanning heads in a certain geometric arrangement, it is possible to measure the systematic error of rotary tables in six dimensions. This paper describes the mathematical transformations between the six measuring quantities and the six errors of the rotary table, and how geometric uncertainties of the sensor set-up influence the system accuracy of the measuring device.
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