多種生產週期時間產品之派工策略-考量機台當機特性

Abstract

晶圓代工廠如果能提供多種生產週期時間產品的服務，不僅可以吸引不同需求的顧客，也可以減少緊急訂單插單的情形。目前相關文獻與實務在遇到短生產週期產品時，是以緊急訂單的方式，給予短生產週期產品優先權，然而如此可能會造成短週期產品提前產出而長週期產品延遲產出的情形。本研究利用方氏修改最小餘裕時間派工法則的觀念，加入考量機台當機特性的影響，修正發展出一個可以控制多種生產週期時間的派工法則，本研究所提的派工法則(Modified_Slack_weight)，藉由分析剩餘加工步驟機台群的利用率、可用率、機台數與機台加工時間，配合等候理論(M/D/S)修正，來找出哪些機台群可能需要較久的等待時間，給予適當權重使得剩餘加工步驟需要等待較久的工單可以優先通過。 模擬結果顯示本研究所提Modified_Slack_weight派工法則，在達交率、總延遲損失利潤、總延遲時間方面，相較於文獻與實務上常用的FIFO、Least Slack、EDD、CR與Slack_weight派工法則，皆有較佳的績效。在生產週期標準差方面，本研究提出的派工法則，相較於FIFO、Least Slack、EDD、也有較佳的績效。

This research develops a dynamic dispatching rule called Modified _Slack_weight for IC foundries in order to improve the on-time delivery rate for multiple cycle time services. Multiple cycle time service is that wafer lots are assigned different committed manufacturing cycle time based on customers’ demands. For example, wafer lots are grouped into three classes：shorter cycle time lots、regular cycle time lots, and longer cycle time lots. Customers can place their orders with a particular cycle time and price. Based on the utilization rate, machine numbers, availability rate of each machine group and the estimated waiting time in each machine group. A particular value of weight is assigned to a machine group. For a particular lot in queue at a certain machine group, we sum up the values of weight of the machine groups that are used to process the remaining steps. And the Modified_Slack_weight of this lot is defined by dividing the slack-time with the total weights. The processing priorities are determined by the value of Modified_Slack_weight. Finally, simulation results show that the proposed Modified-Slack_weight dispatching rule is better than other dispatching methods in literature.