Manufacturing execution system

Manufacturing execution systems (MES) are nowadays also called Manufacturing Enterprise Systems.

Manufacturing Enterprise 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 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 Relations 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

Relationship with level 0,1,2 systems

Systems acting on ISA-95 level 3 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

MES systems connect to real-time data and transaction data (data accumulated into collections to deliver sets of information) in a variety of ways. These systems are typically configured by System Integrators, able to bring their unique knowledge on process, equipment and vendor solutions.

Direct Integration – MES systems include connectivity (communications to plant floor equipment) as part of their product offering. This requires the MES system developers to offer specific support for the variety of plant floor equipment that they want to interface with. MES Vendors must be expert in their own products, and connectivity to other vendor products, often those offered by competitors.

Relational Database (RDB) Integration – MES systems connect to plant floor data sources through a Relational Database Staging Table. Plant floor systems will deposit the necessary information into a Relational Data Base. The MES system will remove and use the information from the RDB Table. The benefit of RDB Staging is that MES vendors do not need to get involved in the complexities of plant floor equipment integration. Connectivity becomes the responsibility of the System Integrator.

EATM (Enterprise Transaction Modules) – These devices have the ability to communicate directly with plant floor equipment and will transact data with the MES system in methods best supported by the MES system. Again, this can be through a staging table, Web Services, or through system specific business system APIs. The benefit of an EATM is that it offers a complete, off the shelf solution, minimizing long term costs and customization.

Custom Integrated Solutions – Many system integrators designs offer custom crafted solutions, created on a per instance basis to meet site and system requirements. There are a wide variety of communications drivers available for plant floor equipment and there are separate products that have the ability to log data to relational database tables. Standards exist with-in the industry to support interoperability between software products, the most widely known being OPC, managed by the OPC Foundation. Custom Integrated Solutions typically run on workstation or server class computers. These systems tend to have the highest level of initial integration cost, and can have a higher long term cost in terms on maintenance and reliability. Long term costs can be minimized through careful system testing and thorough documentation.

Sources

• Managing Automation MES Knowledge Center [1]
• Market Overview: Manufacturing Execution Systems by Forrester Research [2]
• MES: A guide to getting started; PACE-Australia's Process & Control Engineering website [3]
• AutomationWorld, MES Definition Work Continues, March 2006 * [4]

See also

• Manufacturing Operations Management