Geometric Error Identification Method for Swiss-Type Automatic Lathe by Using Reference Sphere and Displacement Sensor

Abstract Accuracy of machined parts are deteriorated due to geometric errors between axes in five-axis machine tools. Therefore, many research works have been carried out to identify and compensate the geometric errors. Swiss-type automatic lathes are widely applied to machine small parts with complex shapes. Although many geometric errors exist in Swiss-type automatic lathes, conventional measurement methods cannot evaluate geometric accuracy due to small working space of the automatic lathes. In addition, the influence of geometric errors onto machining accuracy has not been clarified. In this study, a mathematical model with geometric errors of a Seiss-type automatic lathe that represents the tool tip position in the workpiece coordinate system is developed. The correctness of the model has confirmed through comparing the simulated machined grooves and real ones. A method to identify the geometric errors using a reference sphere and a displacement sensor is also developed based on the model and measurement tests are carried out. As a result, it is confirmed that five geometric errors can be identified by three different measurement methods. It is also confirmed that the measured deviation by the displacement sensor can be decreased by adjusting the coordinate offset parameters on NC controller. Machined shape of the grooves are also be improved by the parameter adjustment based on the identified geometric errors.