Effect of Robot Dynamics on the Machining Forces in Robotic Milling

This paper analyzes the effect of robot structural dynamics on the forces produced in robotic milling. For this purpose, a dynamic milling force model incorporating the effect of robot dynamics and the effect of external forces on the robot stiffness is implemented. The force model employs prior work on dynamic modeling of milling forces where the influence of system compliance on the equilibrium or “steady state” uncut chip thickness is accounted for using iterative computation. The effect of milling forces on the robot arm stiffness is accounted for using the Conservative Congruence Transformation (CCT). Robotic milling experiments show ∼50% to 75% reduction in the predicted errors for key characteristics of the resultant milling forces with the dynamic model. The paper also analyzes the significance of the effect of robot dynamics on the resulting forces as a function of robot configuration (pose) and cutting conditions.