A real time error measuring device for meso-scale machine tools

This paper describes the development of a real time error measuring device for the simultaneous measurement of movement errors in straightness, yaw and roll in a linear machine stage. It was designed specifically for measuring errors in the spatial positioning of meso-scale machine tool stages. The arrangement of the optical path and design of the optical elements make it easy install the device on a linear stage. Roll, yaw and horizontal straightness error motions are sensed using the reflection of a laser beam from a plane mirror. A nonlinear measurement model was derived and simulation analysis showed this could be linearized when the measurement angle error was smaller than 0.05°. The measurement ranges of the proposed system are ±30″ for θx, ±20″ for θy and ±30 μm for the z-axis. The measurement precision was verified using a laser interferometer and an electronic level and the accuracy of the angular error and straightness error measurements were found to be in the range of ±0.25″ and ±0.5 μm respectively. The extended measurement uncertainties (95% confidence level) were: 0.46″ for θx error motion; 0.46″ for θy error motion; and 0.616 μm for straightness.