Analytical modelling and experimental validation of micro-ball-end milling forces with progressive tool flank wear

In this paper, an analytical model for estimating the micro-ball-end milling forces is presented based on experimental investigation of progressive tool flank wear. The wear form and wear mechanism of the micro-ball-end mill are revealed through a series of micro-ball-end milling experiments. The effecting laws of cutting parameters such as feed per tooth, cutting speed, and inclined angle on tool flank wear are investigated. The experimental results indicate that the progressive tool flank wear has significant influence on cutting force in micro-milling of NAK80 steel. To assure the prediction accuracy of micro-ball-end milling force, an analytical methodology is presented to estimate cutting forces which considers not only the shearing force resulted from chip formation but also ploughing and rubbing force resulted by combined elastic contact and plastic flow at enlarged flank wear land. To verify the validity of the developed analytical model, a series of experiments are carried out on high-precision machine by using micro-ball-end mill with different flank wear lands. The comparisons of theoretical and experimental cutting forces indicate that the developed model can provide acceptable predicted accuracy. The proposed analytical cutting force model could be employed to monitor progressive tool flank wear land width in micro-ball-end milling of complex surface in future work.