Iso-phote-based tool-path generation of free-form surfaces for computer-aided design and manufacturing

This dissertation presents new research approaches in generating tool paths for machining free-form surfaces. The central theme is fourfold: (1) to generate iso-phote based tool paths for machining free-form surfaces on three-axis NC machines; (2) to select optimal tools for interference-free sculptured surface machining; (3) to exploit the iso-phote based ruled surface approximation and its application in machining; and (4) to generate streamline approximating tool paths for machining turbine blade surfaces.; In chapters 2 and 3, the concept of iso-phote is introduced to facilitate the tool-path generation. By using the iso-photes as a general partition of the free-form surface, feature based tool paths are achieved. A comparison study of this iso-phote based machining with the conventional machining methods shows favorite result for the new approach.; In chapter 4, a systematic tool-path generation methodology which incorporates interference detection and optimal tool selection is proposed. In this method, the global and local interference is first detected and prevented, and then the optimal tools in terms of machining time are selected. A system of 5 algorithms is developed to determine the interference area. Our case study has demonstrated the validity of the proposed methodology and algorithms.; In chapter 5, a method to approximate free-form surfaces using piecewise ruled surface and its application in 5-axis NC machining are presented. The piecewise ruled surfaces are constructed based on iso-photes. The application of this iso-phote based ruled surface approximation in five-axis NC machining is also studied. The tapered tools are suggested to cut the ruled surfaces. Methods for selecting appropriate tools are presented. Our case studies show that the new approach may lead to an integration of rough, semi-finish and finish machining of free-form surfaces.; Chapter 6 proposes an analytical method for generating tool paths which approximate streamlines. This new approach allows direct control over the starting and the ending tool paths. The intermediate tool paths are automatically generated through a parametric space mapping and a Coons surface patch approximation. Application of this method in turbine blade machining is studied in detail. A software package is written and integrated into the Pro-Engineer CAD/CAM system.