CNC machine tools can simultaneously drive two or more axes of motion along tool path computed by CAD/CAM softwares. Several algorithms have been developed to compute reference points for each axis in real time; due to inertia loads, torque and power limitations of each axis, it is necessary to improve the current algorithms. In order to machine along a free-form tool path, most of machine controllers require that the tool path to be divided into linear and circular segments which approximate the real path. Path segmentation impose a severe computational burden on achieving optimum feed and acceleration rates. Several curve interpolation algorithms have been investigated which are based on approximation methods. Farouki [1] introduced the idea of using Phythagorean- Hodograph (PH) curve in CNC interpolators which offers exact computation of reference points. In his recent research continuos variation of feed rate, and along with physical constraints have been investigated [2]. In this paper, physical constraints on each CNC axis are reviewed. Then, an improved quadratic feed rate algorithm based on arc-length variations is proposed in order to obtain the minimum acceleration length. Lastly, feed dependant cutting forces encountered in real machining are included in the developed algorithm which finds the maximum constant feed rate and the minimum acceleration length

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