Swiss-type automatic lathe widely used to machine small and complex parts for medical and automotive fields. It has multiple axes and tools whose misalignments and tilts of average lines called as geometric errors, yields machining inaccuracy. The Swiss-type automatic lathe has the guide bush, which supports the workpiece near the functional point to avoid workpiece deflection. Although it is known that the guide bush can enhance the machining accuracy by avoiding the workpiece deformation, the effect has not been evaluated quantitatively. In this study, a mathematical model of a Swiss-type automatic lathe considering geometric errors between the axes and a measuring method to measure radial deviations of workpiece during main spindle rotating are developed to evaluate the effect of guide bush quantitatively. The relationships between geometric errors and measured deviations are formulated based on the mathematical model. The workpiece clamping error and the parallelism error between the average line of main spindle and Z-axis are identified from measurement results. Comparing the measurement results with and without guide bush, it is confirmed that the guide bush can eliminate several geometric errors around the workpiece.
Kawai et al. (Wed,) studied this question.