The productivity of machining centers is influenced strongly by the quality of NC programs. To investigate the productivity, an NC program simulator has been developed to analyze and evaluate an NC program by decoding its NC codes. With the simulator, even before the actual machining, the tool paths can be displayed and the operational times occupied in the positioning feed motion and cutting feed motion, etc. can be calculated. The effects of the maximum speed and the acceleration of positioning feed on the productivity have been analyzed. Additionally, the influence of feedrate override function to shorten the operational time has been investigated in the conventional and the high speed cutting, respectively. From the results obtained from analyzing three NC programs, it is found that the effectiveness of the override function depends on the relation among the average moving distance, the commanded feedrate and the acceleration of cutting feed. Especially, in the case of the NC program for machining dies or molds, the productivity will be hardly improved using faster feedrate, because the actual feedrate hardly increases as expected due to the tiny moving distances of NC blocks. High speed & high precision function, which is an advanced optional function, is much more effective not only to improve the productivity but also to keep the machining accuracy of high speed cutting.
