Modeling and Identification of Feed Drive Kinematics and Cycle Time Calculation

Cycle time calculation plays a major role in the design of manufacturing systems. Accurate estimates are needed to correctly determine the capacity of a line in terms of the number of machines that must be purchased. Over estimation results in excess capacity and under estimation leads to unsatisfied demand. Due to the high automation and cutting speeds of modern machining processes, cycle time calculation must consider both the timing of various machining actions and the kinematics of feed motions. This paper presents a cycle time calculation algorithm that gives accurate cycle time results by considering the effects of jerk and acceleration of the machine tool drives. The kinematic model for axis motion is based on trapezoidal acceleration profiles along the toolpaths. Based on this model, an algorithm for identifying the kinematic parameters has been developed. This algorithm has the advantage of utilizing a minimal set of axis motion data thus reducing the amount of data that must be collected from experiments by the machine tool vendor or the machine tool’s enduser. The proposed cycle time calculation algorithm has been verified in machining a V6 cylinder head on a four axis CNC machine.