Abstract
We have developed a new evaluation method to obtain the dynamic characteristics during cutting directly by machining the specific workpiece. We choose an NC lathe as the target machine tool. Three–dimensional cutting forces are generated during turning operation. These cutting forces change periodically when the cross sectional profile of workpiece consists of polygon. Then, the periodic excitation forces are obtained from these cutting forces generated at the contact point between tool and workpiece by this operation. Further, the excited frequency of periodic and sinusoidal forces obtained by machining the non–circle workpiece depends on the workpiece revolution, the desired frequency is to be obtained by changing the spindle revolution variably from DC to maximum revolution. This combination leads the excitation forces in frequency domain to the desired frequency range and enough force amplitude as same as the swept sinusoidal excitation technique. Because 3 equations are obtained by the one measurement, the 6 unknown parameters cannot be solved analytically. The pseudo inverse matrix is used to obtain the approximate solution of the dynamic characteristics by proceed the same measurement at the same position. In this report, the proposed method and its evaluation results by using simple structural model are reported. Further, the calculated results of transfer functions of an NC lathe are introduced.
