A feedrate scheduling algorithm to constrain tool tip position and tool orientation errors of five-axis CNC machining under cutting load disturbances

This paper proposes a model to keep the cutting load induced tool tip position and tool orientation errors of five-axis CNC machines within the desired tolerance limit by scheduling the feed along the tool paths. The cutting forces at the tool tip are transmitted to three translational and two rotary servo drives of the machine tool using its kinematic model. Tracking errors of each axis contributed by cutting forces are modeled using the disturbance transfer function of servo drives. The tracking errors are mapped to the workpiece coordinate system to evaluate the tool tip position and tool axis orientation errors at discrete tool path locations. The cutting forces, therefore the tracking errors, are modeled as a linear function of tangential feed velocity. The feed is adjusted to constrain the tool tip position and tool axis orientation errors at the desired tolerance levels along the tool path. The proposed algorithm has been experimentally validated by milling a curved tool path on a five-axis commercial CNC machine tool. It is shown that the proposed algorithm can significantly improve the part machining accuracy without increasing the machining time. (C) 2018 CIRP.