Arc approximation method is widely used in machining those parts contoured by various complex plane curves. In this paper, several arc approximation methods are reviewed, and the algorithm of the optimum arc approximation, which ensures the continuity of derivatives, is established. The algorithm presented can be used to precisely machine the parts with complex plane curves and the revolving body with a curved surace. In addition, it can also be used in part-programming of CNC machining.
