ロット分割における材料移動とリードタイムのトレードオフを考慮したマテリアルハンドリングルール

摘要

本論文では，オープンショップモデルにおいて，ロット分割によるリードタイムとロットの移動回数のトレードオフをシミュレーション実験によって分析する.一般にはロット分割を行うとジョブの平均リードタイムは短縮するが，システムの負荷やセットアップタイムが大きい場合は，ロット分割のデメリットが顕著化し，分割数を増加しすぎると平均リードタイムが増加する場合があることを示す.また，ロット分割の利点を生かしリードタイムを短縮しながら，同時にロットの移動回数の増加も抑制するマテリアルハンドリングルールとして新たにtime based rule を提案し，数値的にその有効性を検証する.%In this paper, we consider the effect of lot splitting, which is the procedure of splitting a production order into smaller sub-lots that are free to move independently through stages of the manufacturing process. In this lot splitting, there is a trade-off relationship between the material movement and the lead time. We analyze the effect of the lot splitting in simulation experiments under the model of an open shop environment, where there are no restrictions on the order in which the operations of a job are performed. Generally, the average lead time to manufacture the products becomes shorter as a result of lot splitting of each job. However, we show that there are some cases where lot splitting leads to disadvantages, such as when too much lot splitting increases the average lead time when the machine utilization is high and/or the setup time to process the material is relatively long in proportion to the processing time of the jobs. In addition, we propose a new material handling rule, called the time-based rule, which can create the best balance of shorter lead time and less frequent material movement simultaneously. In this time-based rule, we assume that the processing completion time of each production lot is known using radio frequency identification (RFID) to monitor the production progress. The effectiveness of the proposed method is verified in the simulation experiments.