| This dissertation presents algorithms for tool positioning, NC program verification and tool path planning for five-axis NC machining of sculptured surfaces.; The representations and manufacture of sculptured surfaces is a major area of interest in CAD/CAM. Previous work in NC machining of sculptured surfaces was mostly performed on three-axis NC machines with ball-end cutters. This dissertation focuses on five-axis NC machining with cylindrical-end cutters. Such an NC system provides more flexibility and efficiency, particularly for machining free-form surfaces.; Despite the absolute advantages of five-axis over three-axis machining that still need further research for five-axis machines. Those problems are mostly related to gouge avoidance and cusp height reduction.; In the light of this situation, some methods are developed for the control of five-axis NC machining. First, this thesis presents a method of tool placement and orientation for five-axis machining. The algorithm is based on matching the local curvature that is normal to the direction of tool motion with the effective curvature of the tool. It can reduce or eliminate local gouging errors. Second, a newly developed NC program verification algorithm is introduced. The objective of this algorithm is to automate the verification process. With the generated tool position and orientation, a detailed NC program verification process is developed to compute the cusp heights for a given tool path step-over. This realizes the goal of moving the validation process into software and thereby eliminates errors before any machining is attempted. Finally, the tool path planning algorithm is developed for global planning of the adjacent tool passes in order to control the cusp heights within tolerance and achieve high efficiency. This method automatically calculates step-over on each cut according to the requirements of the surface shape.; The algorithms developed by this dissertation will provide the following benefits: (1) a better quality product, because no gouging tool positioning is realized, (2) reduced finishing operations, because the cusp heights are strictly controlled by the software within the specified tolerance, (3) reduced machining time, because the cuts are automatically made closer together where necessary, and farther apart in flatter areas. |
