Development of mathematical model and geometric error identification methods for Swiss-type automatic lathe -verification of geometric error suppression effect of guide-bush-

Modern Swiss-type automatic lathes have a complex configuration: a guide-bush supporting the workpiece, a movable main spindle, and a rotary axis with milling spindles. These components make it possible to machine small, complex-shaped parts such as medical and automotive parts; however, lathes also have many geometric error factors. Thus far, no studies have clarified and identified the geometric errors that exist in lathes. Additionally, the error-suppression effect of the guide bush has not been quantitatively clarified. Therefore, in this study, the geometric errors existing in a Swiss-type automatic lathe were clarified, and a mathematical model considering them was developed. Based on this model, methods for measuring and identifying geometric errors have been developed. It was clarified that the developed method can identify all geometric errors between a workpiece and milling tool in a structural loop. It was also clarified that the guide bush can significantly suppress several geometric errors on the workpiece and main spindle. • This study is the first to model a Swiss-type automatic lathe by considering all the geometric errors in a structural loop and to quantitatively clarify the effect of guide-bush. • Direct and indirect measurements are demonstrated and the calculation method for the geometric errors is described. • The effect of the guide-bush is clearly shown by the identified results, demonstrating the advantages of the Swiss-type configuration.