DESIGN AND IMPLEMENTATION OF HIGH-PERFORMANCE REAL-TIME FREE-FORM NURBS INTERPOLATOR IN MICRO CNC MACHINE TOOL

摘要

This paper provides a suitable methodology to implement a high-performance and precise NURBS interpolator considering machine dynamics. The NURBS tool path curve is realized in real time by mapping the feedrate with a cubic curve with respect to time satisfying the machine dynamics and chord error. This is done by analyzing the feedrate profile offline and scheduling it with respect to time using a time optimal jerk limited algorithm. The proposed and the conventional NURBS interpolators are implemented in a three axis micro machine tool and the machining performance with respect to surface finish at different feedrates is compared. It is found that the feedrate profile obtained using the proposed interpolator scheme results in improved surface finish. Experimental evidences regarding the improvement in surface finish using a NURBS interpolator are shown for the first time according the authors knowledge. The proposed interpolator is designed with flexibility so that it can be implemented in all types of conventional CNC 3 axis machines also.