Machining, Measurement, and Control Laboratory

Graphical presentation of error motions of rotary axes on a five-axis machine tool by static R-test with separating the influence of squareness errors of linear axes
Cefu Hong and Soichi Ibaraki

This paper presents an efficient and automated scheme to observe error motions of rotary axes on a five-axis machine tool by using the R-test. During a five-axis measurement cycle, the R-test sensors nest measures the three-dimensional displacement of a sphere attached to the spindle in the coordinate system attached on the rotary table. This paper first demonstrates an intuitive, graphical presentation method of R-test measurements to understand how error motions of rotary table change in threedimensional space depending on the swiveling angle. A critical issue with the error calibration by the R-test is that error motions of linear axes must be sufficiently small as a prerequisite to calibrate component errors of rotary axes. To partially address this issue, this paper proposes a scheme to separate squareness errors of linear axes by performing a set of R-test measurement cycles with different sphere positions.
Keywords: Five-axis machine tool, R-test, Calibration, Error motion, Squareness error.