| Summary: | 碩士 === 國立臺灣大學 === 工業工程學研究所 === 87 === This research presents a tool portfolio planning method, with technical and economical consideration aspects, to facilitate tool procurement planning in hi-tech industry. Within these aspects, different tools work on different technical processes result in different throughput; ordinary technology demands are rapidly replaced by advanced ones; tool acquisition cost is drastically changed with time. Therefore, the proposed method will generate an optimal tool portfolio combination with respect to the planning horizon, based on the information of the fluctuation of technology demands and the throughput, acquisition cost, and salvage of each tool. At first, feasible solutions of tool portfolios are computed for each period separately. Feasible tool portfolios are linked period by period, to from a hierarchical directed graph. Using the shortest path computation method of graph theory, the optimal tool portfolio combination is computed from dynamic programming. However, when the choice of available processing techniques and type of tolls increases, the solution space expands too large to being solved. Therefore, this research presents an expansion method to produce a manageable set of feasible tool portfolio for computation of a quasi-optimal tool portfolio combination. The expansion method starts with a tool portfolio of optimal cost, which is computed from linear programming methods, to include the neighboring solutions to from the feasible tool portfolio set for each period. The reduced number of feasible tool portfolios reduces the solution space, while sustains a near optimal solution of tool portfolio combination.
The tool portfolio planning method is implemented in the Visual FoxPro programming language. Thirteen study cases are executed to verify the function of the tool planning system. Complicated cases, such as three technologies versus three and four tool types cases, were investigated. To reflect the fact of rapid renovation, cases of various technology demands and tool price fluctuations are studied. And comparisons between exhaust method and the expansion method are made. Tool portfolio planing results from the proposed method reveal the decision of tool replacements, which meets ones anticipation. The proposed method is more practical and useful, compared with the previous research works, sicnce it considers with both technological and ecnmical aspects. Using this planning method, high-tech industry can plan periodically for the optiomal tool portfolio combination, in respose to economical consideration and technology renovations.
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