Prediction of spindle dynamics in milling by sub-structure coupling

The Stability of machining process depends on the dynamics of the machine tool, among other things. However, the dynamics of the machine tool changes when the tool is changed. To avoid the need for repeating the measurements, sub-structuring analysis may be used to couple the tool and spindle frequency response functions. A major difficulty in this approach is the determination of joint stiffness and damping between the two sub-structures. In particular, the measurement of rotational responses (RDOFs) at joints is a difficult task. In this research, a simple joint model that accounts for RDOFs is proposed. It is shown that this model avoids RDOF measurement while taking into account the bending modes. An optimization method based on genetic algorithm is employed to find parameters of the joint model. Receptance coupling analysis is used to couple the machine tool and tool FRFs obtained from experiment and FE, respectively. The RC based response obtained in this way is compared with experimental FRF which shows good agreement and confirms that the joint model has been successful in predicting the tool bending modes.