Automated machining of stepped cylindrical holes using conical helical toolpaths in a modular CNC canned cycle

Abstract A modular CNC canned cycle is presented for the automated machining of stepped cylindrical holes using a single-pass conical-helical toolpath. In each step, the tool expands from the hole center to the final diameter, performing roughing and finishing in one continuous descent. The cycle employs variable-pitch control to maintain stable cutting conditions and supports two feed zones per step with independent spindle and feed parameters. Implemented directly within the CNC controller, the method allows parametric definition of geometry and machining settings without external CAM processing. Analytical modeling, controller simulation, and machining trials on a 3-axis HAAS system verified that the generated trajectories are mechanically stable and reproducible under realistic cutting conditions. The results demonstrate a practical framework for embedding variable-geometry helical machining as a reusable, controller-level routine suitable for standard CNC platforms.