Manufacturing Execution Systems (MES) are computerized systems used in manufacturing. MES can provide the right information at the right time and show the manufacturing decision maker "how the current conditions on the plant floor can be optimized to improve production output." MES work in real time to enable the control of multiple elements of the production process (e.g. inputs, personnel, machines and support services).
"Manufacturing Execution Systems [help] create flawless manufacturing processes and provide real-time feedback of requirement changes," and provide information at a single source. Other benefits from successful MES implementation might include:
Reduced waste, re-work and scrap, including quicker setup times
More accurate capture of cost-information (e.g. labor, scrap, downtime, and tooling)
Incorporate Paperless Workflow Activities
Reduced inventory, through the eradication of just-in-case inventory
A functional hierarchy was defined in which MES were situated at Level 3 between ERP at Level 4 and process control at Levels 0, 1, 2. With the publication of the third part of the standard in 2005, activities in Level 3 were divided over four main operations: production, quality, logistics and maintenance.
Between 2005 and 2013, additional or revised parts of the ANSI/ISA-95 standard defined the architecture of an MES into more detail, covering how to internally distribute functionality and what information to exchange internally as well as externally.
Over the years, international standards and models have refined the scope of such systems in terms of activities, that typically include:
Management of product definitions. This may include storage, version control and exchange with other systems of master data like product production rules, bill of material, bill of resources, process set points and recipe data all focused on defining how to make a product. Management of product definitions can be part of Product lifecycle management.
Management of resources. This may include registration, exchange and analysis of resource information, aiming to prepare and execute production orders with resources of the right capabilities and availability.
Dispatching production orders. Depending on the type of production processes this may include further distribution of batches, runs and work orders, issuing these to work centers and adjustment to unanticipated conditions.
Execution of production orders. Although actual execution is done by Process control systems, an MES may perform checks on resources and inform other systems about the progress of production processes.
Collection of production data. This includes collection, storage and exchange of process data, equipment status, material lot information and production logs in either a data historian or relational database.
Production performance analysis. Create useful information out of the raw collected data about the current status of production, like Work In Progress (WIP) overviews, and the production performance of the past period like the Overall Equipment Effectiveness or any other Performance indicator.
Production Track & Trace. Registration and retrieval of related information in order to present a complete history of lots, orders or equipment (particularly important in health related productions, e.g. pharmaceuticals).
In many cases, MiddlewareEnterprise Application Integration (EAI) systems are being used to exchange transaction messages between MES and Level 4 systems. A common data definition, B2MML, has been defined within the ISA-95 standard to link MES systems to these Level 4 systems.
Relationship with Level 0, 1, 2 systems
Systems acting on ISA-95 Level 2 are Supervisory Control And Data Acquisition (SCADA), Programmable Logic Controllers (PLC), Distributed Control Systems (DCS) and Batch Automation Systems. Information flows between MES and these process control systems are roughly similar:
To PLCs: work instructions, recipes, set points
From PLCs: process values, alarms, adjusted set points, production results
Most MES systems include connectivity as part of their product offering. Direct communication of plant floor equipment data is established by connecting to the Programmable logic controllers (PLC). Often, plant floor data is first collected and diagnosed for real-time control in a Distributed control system (DCS) or Supervisory Control and Data Acquisition (SCADA) system. In this case, the MES systems connect to these Level 2 system for exchanging plant floor data.
^Johann Eder, Schahram Dustdar (2006) Business Process Management Workshops. p. 239
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Enterprise-Control System Integration Part 3: Activity Models of Manufacturing Operations Management. Research Triangle Park, North Carolina, USA: International Society of Automation. 2005. ISBN1556179553.
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