| The multitude of processing capabilities of four-axis CNC turning centers (including parallel and simultaneous machining, automated material handling, and mill/turn capability) significantly complicates optimal process planning. Owing to the variety of constraints to be considered and the large number of alternative process plans for manufacturing a part, manual generation and optimization of process plans is inefficient and time-consuming. As a result, these highly versatile machines are often used in a mass production mode to avoid frequent process planning and, thereby, not utilized to their fullest potential.; This thesis presents the design and implementation of a hybrid computer-intelligent, user-interactive computer-aided process planning (CAPP) system for four-axis CNC turning centers. Two approaches to optimal process planning based on the Nested Partitions (NP) algorithm and Mixed-integer Program (MIP) are developed. Solution quality is compared against the lower bound obtained from a relaxed (MIP) formulation of the process planning problem.; Experiments with sample parts show that the NP algorithm is capable of rapidly generating high quality process plans. On smaller problems, it generates optimal solutions compared to those from the (MIP) utilizing the branch-and-bound algorithm. The results on larger problems suggest that the NP approach is superior to the branch-and-bound algorithm both from solution quality and computational time perspectives.; Additional experiments have been conducted to compare the performance of the NP approach to the Tabu Search (TS) heuristic developed in prior research. Both the NP and TS methods are found to be appropriate within our CAPP framework.; A user-interactive CAPP system has been developed and integrated with a commercial CAM software (Esprit/X). The system enables a process planner to (1) generate high quality process plans rapidly, (2) impose or relax optimization constraints, and (3) modify plans during the optimization process and reoptimize them. The integration with Esprit/X facilitates cutter path and NC code generation for the process plans obtained from the optimizer. |
