Analysis method for investigating the influence of mechanical components on dynamic mechanical error of machine tools

Abstract

In machine tools, the difference between the position of the tool center point and that of position detectors of the control system leads to a dynamic mechanical error, which is obtained as the difference between the feedback-controlled table position and the position of the tool relative to the table (tool–table relative position). In this paper, analysis methods are proposed to roughly determine the component of the mechanical system that causes the dynamic mechanical error. Two methods, a two-encoders method and a four-accelerators method, for investigating the influence of the mechanical component on the dynamic mechanical error are proposed. In both methods, the frequency response function between the feedback-controlled table position and the tool–table relative position is evaluated. By the proposed methods, the dynamic mechanical error of a high-precision machining center in the X and Y directions is analyzed for frequencies up to 200 Hz. It was found that the entire frequency range could be divided into three distinct subranges depending on how the component of the mechanical system influences the dynamic mechanical error at different frequencies. The analysis results indicated that in the low-frequency range, the dynamic response of the driven component plays a dominant role in influencing the dynamic mechanical error. Then, the dynamic mechanical error of the experimental machine was measured for small circular motions. The dynamic mechanical error occurred at the micrometer level. The dynamic mechanical error can be estimated from the frequency response function measured by the proposed method.