Establishment of Mode Shape Database for Machine Tool and its Application in Estimating System Dynamics

Machine tool dynamics has an important role in machine health monitoring, chatter prevention, machining process control, and improvement of manufacturing accuracy. For industrial applications, system dynamics vary with the machining process. To achieve this information during operation, the operational modal analysis (OMA) method, which can observe dynamic performance with output only, has rapidly developed and evolved into transmissibility function-based operational modal analysis (TOMA), with the ratio of outputs used for the estimation of system dynamics. However, this analysis is limited by excitation variance and nature of coherence deformation for the entire system when machining position or posture change. To precisely estimate machine dynamics in process, this study proposes the use of feature fitting from a mode shape database after collection by TOMA. By segmenting the continuous machining process, the variation in system dynamics during operation can be separated into domains under the requirement of machining accuracy. A numerical experiment was performed with a no-damping finite element model of one machining center to verify the feasibility and accuracy of the proposed method. Subsequently, the experimental performance of the mode shape with several accelerometers was evaluated, and the differences with finite element results were discussed with further consideration of application in practice.