Due-date performance improvement using TOC’s aggregated time buffer method at a wafer fabrication factory

Due-date performance is one of the most important production indexes for success utilized by wafer fabrication factories. Traditionally, the industry sets a specific due-date tightness level and a dispatching rule based on the total processing time, the production capacity, pre-defined order release criteria and historical data, to ensure deliveries are made on-time. However, such policies typically do not solve the due-date performance problem at wafer fabrication factories, since the processes are highly complex. This investigation explores the due-date performance problem using the concept of the aggregated time buffer in critical chain project management (CCPM), which was developed by Dr. Goldratt. A simulation model was constructed and the performance of the proposed method is evaluated based on four dispatching rules at a wafer fabrication factory. The findings reveal that applying aggregated time buffer control system improved the overall due-date control, in terms of on-time delivery rate, average tardiness, and variances in average tardiness and lateness.