Optimization of material removal rate in milling of thin-walled structures using penalty cost function

Abstract

The high flexibility of thin-walled structures makes their machining process prone to chatter and excessive vibrations. This challenge is compounded by the continuous varying dynamics of the workpiece as material is removed from the workpiece. As a result, the common optimization methods that are used for maximizing material removal rate in the milling processes of rigid parts are not applicable to machining of thin-walled structures. In this paper, an optimization method is presented to maximize the material removal rate in milling of thin-walled structures without violating forced vibration and chatter stability constraints. The cost function of the optimization problem is formulated using penalty terms to impose the vibration constraints. Moreover, a resampling strategy is implemented to minimize the risk of convergence to a local minimum. The performance of the presented approach is studied through planning of the semi-finishing stage of machining a thin-walled pocket structure. The dynamics of the workpiece is modelled using finite strip modelling to ensure high computational efficiency. The numerical simulations and experimental studies in this work show that the presented optimization approach can be effectively used to plan an optimum machining process for thin-walled structures which does not cause chatter or excessive vibration amplitudes.