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In recent years, the demands for mirror finishing by cutting have increased, because the surface quality requirement in die and mold has become severer. In order to realize mirror surface finish by cutting, it is necessary to reduce the influence of tool non-repeatable run-out (NRRO) on machining surface. Rolling bearings used in a spindle for machine tools may cause NRRO of cutting tool due to rolling element revolution. In order to reduce the influence of NRRO on machining surface, an excitation system which can generate counter excitation force has been proposed in this study. The gradual change of multiple peaks of NRRO in frequency domain was observed. Excitation experiment results confirmed that the proposed excitation system can reduce NRRO from the relative displacement between the table and the tool. Furthermore, actual cutting results confirmed a correlation between NRRO reduction of the relative displacement and NRRO reduction on the machined surface. more...

In recent years, the surface quality requirement in die and mold has become severer. In addition, die and mold with surface structure are increasing and it makes polishing process difficult. In order to realize mirror surface finish by cutting, it is necessary to reduce influence of tool non-repeatable run-out (NRRO) on machining surface. Rolling bearings are widely used for machine tools, NRRO of a spindle due to rolling element revolution depends on spindle conditions such as rotational speed, temperature, and cutting load. In order to reduce influence of NRRO on workpiece surface, a prototype of an excitation system which can generate counter excitation force is proposed in this paper. The tool run-out during machining was measured and the results confirmed that the machined surface was affected by this NRRO. In addition, it was confirmed that NRRO has multiple peaks in frequency domain and the state of each peak changes even at the same spindle speed. After developing an excitation system with a voice coil motor, it was confirmed effectiveness of the system that can reduce NRRO component from measured tool run-out signal. more...