Ballbar based geometric error measurement and uncertainty analysis of rotary axis for five-axis machine

Abstract

The ballbar is currently the most widely used instrument for identifying and measuring rotary axis geometric errors, but the measurement results are unreliable due to measurement defects. So the geometric error measurement and uncertainty evaluation method based on ballbar is proposed. Firstly, the radial, tangential and axial measurement are carried out with the ballbar, and the geometric errors are identified according to the eccentricity and deviation of the trajectory. Then, by clarifying the mechanism of uncertainty caused by the tool setting error, ballbar installation error and translational axis error, the evaluation model is established. Finally, this study uses the Monte Carlo method to analyze the measurement uncertainty. The results show that the tool setting error and translational axis error are the main sources of measurement uncertainty, and the measurement uncertainty of the angular positioning error is the largest, which is contributed by the sine and cosine terms in the error identification equation.