A new approach to identifying the dynamic behavior of CNC machine tools with respect to different worktable feed speeds

• An operational modal identification was proposed to predict the dynamics of an machine tool at different feed speeds.
• Modal parameters of the entire machine tool structure in different running states were compared.
• The compared results show that the feed movement of worktable affects some modes of the machine tool.
• The natural frequencies and damping ratios of the worktable decrease obviously as the feed speed increases.

The dynamics of the machine tool structure are important in high precision machining. Some researchers have studied that the dynamics are expected to change under different machining conditions. However, the dynamic behaviors of the machine tool at different worktable feed speeds are rarely studied. In this paper, an output-only modal identification available to predict the dynamics of the machine tool at different feed speeds is proposed. The excitation of this method uses the inertia force sequence caused by random idle running of the worktable. The first six modes of the entire machine tool structure are estimated using the proposed method. The results indicate that the running state of the worktable can influence the modes in which the worktable vibrates. The estimated natural frequencies and damping ratios decrease obviously as the feed speed increases. Furthermore, because this method enable to determine modal parameters by measuring the response of machine tool structure without using any artificial excitation, it can be used to predict the dynamic behaviors of the machine tool in entire working space effectively.