Prediction of Nonlinear Micro-Milling Force with a Novel Minimum Uncut Chip Thickness Model

Abstract

The minimum uncut chip thickness (MUCT), dividing the cutting zone into the shear region and the ploughing region, has a strong nonlinear effect on the cutting force of micro-milling. Determining the MUCT value is fundamental in order to predict the micro-milling force. In this study, based on the assumption that the normal shear force and the normal ploughing force are equivalent at the MUCT point, a novel analytical MUCT model considering the comprehensive effect of shear stress, friction angle, ploughing coefficient and cutting-edge radius is constructed to determine the MUCT. Nonlinear piecewise cutting force coefficient functions with the novel MUCT as the break point are constructed to represent the distribution of the shear/ploughing force under the effect of the minimum uncut chip thickness. By integrating the cutting force coefficient function, the nonlinear micro-milling force is predicted. Theoretical analysis shows that the nonlinear cutting force coefficient function embedded with the novel MUCT is absolutely integrable, making the micro-milling force model more stable and accurate than the conventional models. Moreover, by considering different factors in the MUCT model, the proposed micro-milling force model is more flexible than the traditional models. Micro-milling experiments under different cutting conditions have verified the efficiency and improvement of the proposed micro-milling force model.

Micro-Milling Tool Wear Monitoring via Nonlinear Cutting Force Model

“…The friction force coefficients K c,vb and K r,vb represent the relationship between the flank wear width and the friction forces in the flank wear region. A detailed discussion of the nonlinear shear-ploughing coefficients could refer to in study [25]. The friction force coefficient refers to the study [15].…”

“…Zhou et al [24] built a semi-analytic model to reveal the nonlinear impact of the wearvarying cutting edge on the cutting force. In our previous work, a mechanistic model with an analytic minimum uncut chip thickness is constructed to reveal the nonlinear effect of cutting-edge radius on the micro-milling force [25]. Those studies have laid a theoretical foundation for nonlinear micro-tool wear monitoring.…”