A 3-axis tool path generation algorithm for free-form surface models including defects, such as gaps and overlaps is presented in this paper. To avoid the difficulty of computing a complete cutter location (CL)-surface, the proposed approach generates a tool path by slicing CL-elements instead of a complete CL-surface. A key feature of the proposed approach is that it reduces the number of CL-elements to be sliced by utilizing the correspondence information between CL-elements and cutter contact (CC)-elements. This feature significantly improves the computational efficiency of the proposed algorithm. Empirical tests show that the proposed approach is robust to geometric defects of CAD models, gaps and overlaps, with a near O(n) time complexity, where n is the number of slicing planes.