Development of a multi-phase spindle motor with active damping for chatter reduction

High chip removal rates in machining are often limited by chatter vibrations. While active damping in spindles may mitigate chatter, existing approaches reduce the drive power by occupying axial space. The ratio of damping to drive power is fixed, which limits in-process adjustability. This study proposes a novel spindle concept featuring a ‘bearingless’, multi-phase motor, enabling simultaneous high-performance drive characteristics and adaptive active damping without compromising spindle length or power capacity. Multi-phase motors are typically investigated at power levels below 10 kW, constraining their applicability to high-performance machining. In contrast, this study realized the concept by rewinding the stator of a commercially available 25 kW spindle. Experimental validation demonstrated a reduction in shaft deflection in response to frequency disturbances up to 650 Hz, with no impact on spindle speed, indicating significant potential for chatter reduction.