Novel Hybrid Composite Spindle Shaft for Horizontal Peripheral Milling: A Dynamic Behavior Analysis and Surface Roughness Assessment

Abstract Vibration damping in machine tool spindle systems is vital for suppressing dynamic instability during severe intermittent cutting operations. While carbon fiber reinforced polymer (CFRP) composites have been explored for high-speed vertical spindles and external damping attachments, their direct integration within horizontal spindle shafts for conventional tangential milling remains unprecedented. Addressing this gap, this paper introduces a hybrid CFRP horizontal spindle shaft achieving a 55.5% reduction in rotating mass and an exceptionally high damping ratio of 14.58% and delivers a comprehensive real-world experimental assessment of its dynamic response and workpiece surface finish. The findings reveal that under high-speed cutting regimes 1560 rpm, the hybrid shaft acts as a passive structural filter, suppressing high-frequency resonant peaks (350--450 Hz band) and unlocking significant performance gains essential for high-productivity machining. Under high material removal rates, peak surface topography metrics are substantially enhanced, reducing Rz by up to 27.5% and Rt by up to 34.2%. Furthermore, the particular physical conditions governing the process, including low feed-per-tooth regimes, are thoroughly mapped using orthogonal orbital trajectories (R), FFT spectra, and surface topography. These insights demonstrate the viability of hybrid CFRP shafts for boosting productivity in tangential milling while defining clear operational boundaries for industrial adoption.