Process analysis and tool wear monitoring with spindle motor power and current signals in longitudinal and face turning

This study presents process analysis and tool wear monitoring using spindle motor power and current signals in longitudinal and face turning. To achieve these tasks, longitudinal and face turnings with different levels of flank wear (new, VB150, VB300) were performed. In longitudinal turning, two workpieces with different diameters (Ø80 and Ø45 mm) were used. In face turning, two feed directions (uphill and downhill) were attempted. The spindle motor power, current and speed, as well as cutting forces were recorded in real time during turning. In longitudinal turning, the spindle motor power was found to be sensitive to the level of flank wear, which can be used for tool wear monitoring. Reliable cutting force prediction from spindle motor power (air cutting power + net cutting power) is also shown. In face turning, the tool exit time in the spindle motor power signal was found to be sensitive to tool geometry changes due to wear, suggesting that it can be used for tool wear monitoring. The spindle motor current and speed signals for all turning cases are also analyzed. The influence of the corresponding three-phase spindle motor connections (star and delta) on tool wear monitoring is discussed.