Development of a measuring method for motion accuracy of NC machine tools using links and rotary encoders

An instrument capable of measuring arbitrary NC tool paths in a three-dimensional space has been developed. This paper describes the structure of the newly developed device and an estimation method for determining the 11 error parameters associated with the link length errors and the inclination of the link axes. The estimated error parameters were applied to tool-path trajectories that were calculated from rotary encoder output angles.The apparatus was employed in several measuring experiments, including measurements of square and circular paths for a vertical machining center. The results from these experiments support the validity of this measurement apparatus and the error parameters estimation method.