Compensation of position-independent geometric errors of an index table by linear axes circular tests at different angular positions

We propose a measurement method for improving the accuracy of a horizontal machine tool by compensating for position-independent geometric errors using a double ball-bar, including offset errors and squareness errors in the index table. The measurement requires control over two linear axes simultaneously at different angles of the index table; however, the measured position-independent geometric errors are not affected by the accuracy of the linear axes because of the measurement paths and the analysis approach. Therefore, the method described here enables more robust and accurate measurement results compared with existing approaches. We apply the method to a horizontal machine tool with an analysis of measurement uncertainty. The accuracy of the machine tool is improved significantly by compensating for the measured position-independent geometric errors.