Comparing the kinematic efficiency of five-axis machine tool configurations through nonlinearity errors

Five-axis CNC machines represent a particular class of machine tools characterized by superior versatility. Little attempts were made in the past to compare directly their performances through a common indicator. In this sense, the present study proposes nonlinearity error as a valuable method to quantify the kinematic efficiency of a particular five-axis configuration. Nonlinearity error is defined as the maximum deviation of the cutter-location point from the reference plane generated by the initial and final orientations of the tool during linearly interpolated motions of the cutter along the intended tool path. The proposed concept has demonstrated that nonlinearity error occurs approximately around the middle of the linearly interpolated interval and therefore has validated the current post-processing practice of halfway cutter-location point insertion. The employment of nonlinearity error in the evaluation of the kinematic efficiency of vertical spindle-rotating five-axis machine tools revealed that for an identical machining task, configurations involving the vertical rotational axis tend to move more than those involving only horizontal rotational axes. (C) 2011 Elsevier Ltd. All rights reserved.