Temperature Stabilized Vibration-Based Condition Monitoring of Machine Tool Spindles

Temperature has a strong influence on spindle vibration behavior, yet most vibration-based condition-monitoring practices do not account for thermal stabilization. Through controlled measurements on two representative spindle systems — a naturally cooled high-speed electro-spindle and an oil-cooled direct-drive spindle — this study demonstrates that vibration RMS levels and defect-related spectral features can change by up to 40–87% from cold-start to thermal steady state. To address this, we introduce the thermal time constant as a quantitative and robust metric for identifying when a spindle has reached temperature-stabilized operating conditions. First-order exponential fits to housing temperature measurements show that [Formula: see text] decreases with spindle speed and differs significantly across spindle types, reflecting differences in thermal mass and cooling effectiveness. Spectral analysis further reveals that peak defect magnitudes stabilize only after approximately 2[Formula: see text]–3[Formula: see text], matching trends seen in RMS stabilization. Using [Formula: see text] therefore enables reliable prescription of warm-up times and prevents misclassification of temperature effects as health degradation. The proposed framework provides a practical, measurement-driven approach for establishing temperature-stabilized vibration monitoring protocols for diagnostics and prognosis.