A measuring device for experimental modal analysis of thin-walled workpieces on five-axis milling machines

During the milling process of flexible structures, such as thin-walled profiles manufactured for the aerospace industry, the dynamic behavior of the workpieces can become a key factor that limits the productivity of the machining process. Therefore, knowledge of the dynamic characteristics of the components prior to the milling process is important and provides the possibility to choose appropriate values for the process parameters. The experimental modal analysis is an adequate procedure to study the dynamic properties of components under vibrational excitation. In this process, the response of the structure is measured at defined points under controlled conditions when the structure is artificially excited by an input force. In case of thin-walled components, the response should be measured in a contactless way using laser systems to avoid the disturbance of the moving sensor mass. In order to design this process to be manageable, a device was designed connecting the laser system to the spindle of the milling machine. In this paper, the device, the experimental setup, and the software developed for programming corresponding NC paths are presented. The practicability of the system is also demonstrated analyzing the dynamic behavior of a turbine blade on a five-axis milling machine.