A hybrid design methodology utilizing digital-physical prototyping in the CNC machine tool design process

The primary objective of this study was to investigate the dynamic behavior of a CNC milling machine through a comprehensive experimental and numerical approach, with particular emphasis on vibration damping and dynamic stiffness. A methodology for assessing these parameters was developed, which can be applied to both small and large-scale machine tool structures, highlighting their importance as key design criteria in modern CNC machine development. The research employed an integrated strategy combining numerical modeling and experimental modal analysis (EMA). EMA was performed using different excitation techniques, including an impact hammer and an electrodynamic shaker, while modal parameters were estimated using the Least-Squares Complex Frequency (LSCF) method. The process began with numerical simulations to predict natural frequencies and mode shapes, followed by a two-stage experimental analysis: identification of natural frequencies and damping ratios, and verification of dynamic compliance at the spindle tip. The results revealed a strong dependence of natural frequencies and damping characteristics on spindle position. The lowest natural frequency exceeded 130 Hz, significantly higher than typical fundamental modes of heavy machine tool frames (20–40 Hz). Modal damping reached up to 12%, with an increase of approximately 50% in the upper slider position. The aluminum table exhibited up to four times lower damping compared to the gantry structure. Forced excitation at the tool tip suppressed some modes observed in impact testing while exposing technologically relevant ones. Incorporating frequency-dependent damping into finite element harmonic response analysis yielded dynamic stiffness predictions consistent with experimental results (≤ 10%). These findings underscore the critical role of dynamic parameters in machine tool design and their direct impact on machining accuracy and productivity. The proposed methodology provides a basis for further research into the design of similar CNC machines.