Reliability analysis of micro milling accuracy based on flexible force model

In the process of micro milling, the micro cutting tool is deformed by milling force, causing the decrease of both surface finish quality and machining accuracy of the workpiece. Therefore, it is necessary to study the micro cutting mechanism and deformation of cutting tool. Moreover, traditional micro milling process analysis is based on the assumption that micro milling system parameters are deterministic. However, the parameters of the micro milling system are uncertain due to variations in manufacturing and assembly processes, which in turn affect actual micro milling accuracy. To overcome these drawbacks, the accuracy analysis and reliability analysis of micro milling considering tool deformation are carried out in this paper. The cutting tool is modeled as a cantilever beam with variable cross-section to calculate tool deflection and axial error of machined surface caused by tool deflection. To analyze the coupling effect of milling force, deflection and axial error, an iterative algorithm using the Mean Square Error (MSE) of chip thickness of two continuous tooth paths is proposed for convergence measurement. The model is realized in the form of calculation program to predict the cutting force. The results of prediction model are verified by engineering machining experiments. Considering impact of uncertain factors, this paper presents a practical method for probabilistic analysis for accuracy of the micro milling process based on Subset Simulation (SS) method and Monte Carlo Simulation (MCS) method, in which the influence of various parameters on micro milling accuracy is evaluated.