Operational diagnosis of spatial vibration response in a frame-based self-built CNC milling machine using spectral analysis

This study reports a multi-location, tri-axial vibration assessment of a frame-based self-built CNC milling machine using measured time histories and power spectral density (PSD) plots. Responses were compared at the spindle-support, frame, worktable, and base/support regions while preserving the machine-axis directions. The reported spectra contain recurring low-to-mid-frequency components near 5–10, 9–18, 22–24, and 35–40 Hz; because the first two intervals overlap and the raw records are unavailable in the supplied scientific record, these intervals are treated as descriptive spectral clusters rather than independent analysis bands. The spindle-support measurements show the largest plotted peak amplitudes in the x and z comparisons, whereas the spatial rankings differ by axis. These observations are consistent with direction-dependent structural compliance, but they do not by themselves identify a unique excitation source or causal transmission path. The study therefore provides an evidence-constrained case assessment and identifies the acquisition metadata, repeated-run statistics and synchronized measurements required for a quantitative transmission analysis.