Fab performance

To remain competitive and to boost profitability, manufacturers in capital-intensive and highly competitive industries want to maximize throughput and minimize flow time. Achieving high throughput conflicts with achieving low flow time. In order to unhide the tradeoff between throughput and flow time, a performance measure, called manufacturing performance, has been developed. The manufacturing performance is defined by the quotient of the ratio between throughput and flow time of an actual manufacturing system and this ratio of a reference system. The reference system can be adapted by the user in correspondence with objectives. By applying the manufacturing performance to one workstation and using analytic approximations for this workstation, manufacturing performance can be expressed analytically. It seems that manufacturing performance has an optimal value that is given by equipment availability and coefficient of variation. Manufacturing performance is applied also to a four-workstation manufacturing line. Results from analytic approximations show the practicability of the manufacturing performance. Comparison of manufacturing performance with overall fab efficiency, an earlier proposed metric, showed that the manufacturing performance is a more clear metric. This conclusion was based upon simulations with a two-stations manufacturing line. The manufacturing performance is a technical performance metric for manufacturing lines that supports, for instance, economical considerations to obtain optimal throughput-flow time combinations under economical optimal results. This is a useful addition to the existing metrics, which may benefit manufacturers in their operations. The authors consider this contribution as a discussion paper and demand for comment. Index Terms--Fab performance, manufacturing performance, overall fab efficiency (OFE), performance measures.