Nowadays to survive in the global market with increasing and fierce competition, the keys to success for the companies are fast product and reliable delivery that are the challenges for shop floor control. As one of the most important key performance indicators (KPI), work-in-process (WIP) attracts more and more attention since it has a major influence on overall manufacturing costs. According to Little’s Law, a lower WIP level leads to a shorter production cycle time given the same throughput, which has significant economic importance. Besides that, due date commitment is another critical factor, especially for customer oriented companies to achieve customer satisfaction. A missed due date causes not only penalty, but also confidence lost to the customers. In order to gain a competitive position within industry, on the shop floor enormous efforts have been spent in developing different kinds of operational control strategies relating to WIP and due date. On one hand, there are a number of operational control strategies which target the control of the flow of lots through wafer fab to achieve balanced WIP like CONstant WIP (CONWIP), Starvation Avoidance (SA), or Minimum Inventory Variability Scheduling (MIVS). These WIP oriented rules attempt to avoid starvation and congestion of work-center or operation, thus reducing WIP variability and cycle time. On the other hand, there are also a number of dispatching rules targeting due date control like Earliest Due Date (EDD), Critical Ratio (CR) and Operation Due Date (ODD). These due date oriented rules focus on progressing lot toward on-time completion based on lot status. As WIP and due date have two different goals, even conflicting goals under certain circumstances, the first set of WIP oriented rules do not always lead to good on-time delivery performance, the latter due date oriented rules do not primarily lead to low WIP level. Both WIP oriented and due date oriented rules turn out to be insufficient when both targets, i.e., lower WIP level and lower cycle time, better on-time delivery and less tardiness, are desired simultaneously. As a matter of fact, on the shop floor the challenges to apply WIP oriented or due date oriented rules are way beyond our anticipation. We encounter plenty of questions that cannot be answered with satisfaction from existing literature, when we manage to apply WIP oriented or due date oriented rules. The motivation of this dissertation is to find out the answers for the concerned issues relating to WIP and due date from industry. Particularly, we have a stronger interest in WIP related issues and intend to carry out a comprehensive study about WIP, for the reason that for instance low WIP level in combination with low variance can make sure the lots finish before their due dates as much as possible. Naturally, the due date related issues (on-time delivery and tardiness) can be solved perfectly. We will address the following eight issues and attempt to find out the answers in this dissertation.    «

Nowadays to survive in the global market with increasing and fierce competition, the keys to success for the companies are fast product and reliable delivery that are the challenges for shop floor control. As one of the most important key performance indicators (KPI), work-in-process (WIP) attracts more and more attention since it has a major influence on overall manufacturing costs. According to Little’s Law, a lower WIP level leads to a shorter production cycle time given the same throughput,...    »