Application of classical and output-only modal analysis to a laser cutting machine

This paper presents the application of classical modal analysis and output-only modal analysis techniques (Stochastic Subspace Identification and Frequency Domain Decomposition) to a laser cutting machine. It will be shown that the classical modal analysis gave fundamental insight into the structural dynamics of the laser cutting machine, while the output-only modal analysis from operational vibration data provided the modes of vibration directly influencing the cutting results. From the operational data an additional mode of vibration was identified that could not be extracted by the utilized classical modal analysis techniques. It was revealed that this mode of vibration was nonstructural and that it was caused by the drives and the control system of the laser cutting machine. Furthermore, this nonstructural mode could directly be linked to imperfections of the cutting results for specific machine movements. With this knowledge a cost effective and easy to implement solution was developed that significantly enhanced the quality of the cutting results.