Dynamic Modeling for Control of the Milling Process

In the interest of maximizing the metal removal rate and preventing tool breakage in the milling process, it has been proposed that fixed gain feedback controllers, which manipulate the feed rate to maintain a constant cutting force, be implemented. These process controllers have resulted in substantial improvements in the metal removal rate; however, they may have very poor performance when the process parameters deviate from the design conditions. To address these performance problems, an empirical second order model of the force response for a milling system to feedrate changes is presented along with experimental results which show that the parameters of this model vary significantly with cutting conditions. These variations are shown to have significant effects on the performance of fixed-gain proportional plus integral action and linear model following controllers. This is demonstrated using machining tests as well as through digital simulations.