Overall throughput effectiveness metric for factory-level performance monitoring and bottleneck detection

Seiichi Nakajima provided overall equipment effectiveness (OEE) to measure productivity and perform diagnostics at the equipment level. However, a literature review indicates that such metrics are lacking at the factory level. In order to address this gap, an overall throughput effectiveness (OTE) metric is developed. The purpose of OTE is twofold: it measures factory-level performance and can also be used for performing factory-level diagnostics such as bottleneck detection and identifying hidden capacity. The task of coming up with such a metric was achieved by defining a set of commonly occurring predefined subsystems including series, parallel, assembly and expansion. OTE was developed for each of these predefined subsystems. It also accounts for subsystems processing multiple products and performing rework. Any factory layout can be modelled using a combination of the predefined subsystems, which allows determination of the overall factory effectiveness (OFE). More importantly, OTE has the potential to automate the entire factory-level performance diagnostics, hence drive continuous productivity improvement quantitatively. This paper explains the OTE development methodology, validates the developed OTE metrics and demonstrates its diagnostic ability. Application of OTE to a wafer fab and glass manufacturing case study showed that productivity bottleneck and opportunities for improvement can be identified quantitatively.