For nearly 20 years, computerized manufacturing execution systems (MESs) have played a central role in effective manufacturing management. Originally designed to provide first-line supervision management with a visibility tool to manage work orders and workstation assignments, the MES has evolved into the indispensable link between the full range of enterprise stakeholders and the real-time events occurring in production and logistics processes across the extended value chain.
There are major business issues driving the expanding use of these systems, including demand-driven manufacturing, real-time enterprise objectives, and intelligent enterprise applications. Less adversarial and more inclusive managerial approaches, such as collaborative planning, forecasting, and replenishment (CPFR) and collaborative manufacturing product life-cycle management (PLM) have greatly expanded the user audience that depends on MES information support to do their jobs. MESs are integral to the intelligent enterprise because they manage and record the events in processes and logistics as they're occurring, providing an information source that's current and accurate in near real time.
In this article, I'll describe the essential functions of an MES, focusing on aspects that will be important to organizations as they expand MESs use to achieve business and managerial objectives. Although the names given to the various components of the MES vary greatly among industries and even among companies in an industry, the functions and the information collected in the systems fall into similar categories. Most broadly, the MES is the collection of business processes that provide event-by-event, real-time execution of the planned production requirements — that is, the calculation of how many and what to produce — as received from the enterprise resource planning (ERP) level. A more narrow definition would be that an MES serves as a work-order-driven, work-in-process tracking system that manages and monitors production events and reporting activities.
Manufacturing experts have traditionally employed a three-level pyramid to illustrate the hierarchical nature of systems within the manufacturing enterprise (see Figure 1). The lines between the layers are becoming less distinct as vendors extend their applications, but the current condition in most plants will resemble this structure.
FIGURE 1 Hierarchy of systems within the manufacturing enterprise.