NURBS interpolator for constant material removal rate in open NC machine tools

Conventionally used linear or circular interpolators are undesirable for the precision machining of 3D free-form surfaces for the following reasons: the transmission errors due to the huge number of point data, discontinuity of curve segmentation, and unsmooth motion speed. In this regard, modern CNC machine tools are designed with a function for machining arbitrary parametric curves. However, these systems do not consider controlling feedrate adaptively, which dominates the quality of the machining process. This paper proposes a NURBS interpolator based on the adaptive feedrate control for the constant material removal rate. This is accomplished by varying feedrate using the curvature of a surface. The curvature-compensated feedrate system has important potential applications in ensuring part accuracy and protecting the cutting tool. The simulated and experimental results show it is applicable to real machining.