Abstract: A tool path planning method is proposed based on geometric models of constant scallop-height tool path.To get the offset point-set and scallop point-set,the measured data are offset with tool radius and scallop-height respectively at first.Then the tool envelope surface is constructed using the last tool-path as the center curve,and the transition point-set is acquired by calculating the intersection of the tool envelope surface and the scallop point-set.Subsequently the tool envelope surface is again constructed using the transition point-set as the center curve,and the adjacent tool-path is acquired by calculating the intersection of the tool envelope surface and the offset point-set.All tool paths can be determined by repeating the above steps.Finally the validity of the presented method is demonstrated with two examples.The calculation results are compared with those of iso-planar machining.The results indicate that the path-length is shorter, and the machining efficiency can be enhanced greatly.