Model-based Predictive Force Control in Milling

Milling is a manufacturing process for machining metals, where a milling tool cuts metal from a workpiece. Especially during rough milling the productivity is significantly affected by the process force that acts on the tool. The process force depends on the feed velocity and the engagement conditions. The latter are defined by the path that the tool takes through the metal. Consequently, the feed velocity of the cutter is a suitable manipulated variable. A force model describes the relation between the process force, the engagement conditions and the feed velocity. A separate machine model describes the behavior of the machine tool axis and its numerical controller. Based on these two models a model predictive controller (MPC) is examined, which controls the feed velocity with respect to the predicted process force. The model predictive force controller is applied and validated on a machining center. The mentioned approach is the first implementation of a MPC which explicitly controls the active force in milling.