Manufacturing execution system
Manufacturing Execution Systems (MES), are information technology systems that manage manufacturing operations in factories. 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.
- Scheduling (production processes). These activities determine the production schedule as a collection of work orders to meet the production requirements, typically received from Enterprise resource planning or specialized Advanced planning and scheduling systems, making optimal use of local resources.
- 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)
History
In the early 1980s MES concepts originated from data collection systems. A wide variety of systems arose using collected data for a dedicated purpose. Further development of these systems during the 1990s introduced overlap in functionality. Then the Manufacturing Enterprise Solutions Association (MESA) introduced some structure by defining 11 functions that set the scope of MES. Early 2000 the ANSI/ISA-95 standard merged this model with the Purdue Reference Model (PRM). 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. Activities in level 3 were divided over four main operations: Production, Quality, Logistics and Maintenance. Additional 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.
Relationship with other level 3 systems
The collection of systems acting on the ISA-95 level 3 can be called Manufacturing Operations Management Systems (MOMS). Apart from an MES these are typically Laboratory Information Management System (LIMS), Warehouse Management System (WMS) and Computerized Maintenance Management System (CMMS). From the MES point of view possible information flows are:
- To LIMS: quality test requests, sample lots, statistical process data
- From LIMS: quality test results, product certificates, testing progress
- To WMS: material resource requests, material definitions, product deliveries
- From WMS: material availability, staged material lots, product shipments
- To CMMS: equipment running data, equipment assignments, maintenance requests
- FROM CMMS: maintenance progress, equipment capabilities, maintenance schedule
Relationship with level 4 systems
Examples of systems acting on ISA-95 level 4 are Product Lifecycle Management (PLM), Enterprise Resource Planning (ERP), Customer Relationship Management (CRM), Human Resource Management (HRM). From the MES point of view possible information flows are:
- To PLM: production test results
- From PLM: product definitions, bill of operations (routings), electronic work instructions, equipment settings
- To ERP: production performance results, produced and consumed material
- From ERP: production planning, order requirements
- To CRM: product tracking and tracing information
- From CRM: product complaints
- To HRM: personnel performance
- From HRM: personnel skills, personnel availability
In many cases, Middleware Enterprise 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 PCS: work instructions, recipes, set points
- From PCS: 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. The industry standard for plant floor connectivity is OLE for process control (OPC).
Sources
- Manufacturing Enterprise Solutions Association [1]
- International Society of Automation [2]
See also