| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 93 === Because of the advent of 12-inch semiconductor wafers, the automated material handling system (AMHS) becomes a necessary investment to the industry. The main evaluation methods for most of production equipments are normally based on the investment return. For those non-productivity equipment investments, the investment returns are difficult to estimate since they do not produce products. Therefore, the evaluations of the AMHS are mostly focused on the minimization of the total traveling distance. However, the shortest traveling distance does not guarantee the best efficiency. Of course, it does not lead to the best investment return.
The main purpose of this study intends to evaluate an AMHS from the investment return viewpoint. This study includes two parts. In part I, by adopting the concept of the Little''s law, the system efficiency due to the installation of an AMHS can be quantified. The resulting efficiency can either be from the increase of the throughput, or the decrease of the WIP inventory. The former makes extra sale profit, and the latter saves the WIP inventory cost. In part II, based on the theory of constraints (TOC), TOC product costing and profit estimation formulations are established. The investment return years can then be estimated by dividing the sale extra profit to the investment for the case of the throughput increase, or by dividing the saving inventory cost to the investment for the case of the WIP inventory decrease. For the purpose of demonstrating the proposed method, a specified simulation case is performed and the years of returns are estimated one by one for different market prospects at last.
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