Management + Systems

MES and ERP are two of the most widely recognised acronyms for digital systems in the manufacturing world; yet defining the interrelated roles of these two systems is challenging. Here, Siemens Digital Industries Software looks at why the interaction between MES and ERP software is critical to a manufacturer’s productivity.

Integration of Manufacturing Execution System (MES) and Enterprise Resource Planning (ERP) systems enables their complementary functionalities to bring greater benefits to a manufacturer than siloed systems. A basic understanding of the relationship between these two systems helps customers get the most out of digital investments.

At the broadest level, the relationship between a MES and its ERP counterpart has been defined since the 1990s by ISA-95, the international standard for the integration of enterprise and control systems. ISA-95 incorporates a layer model of technology and business processes for manufacturing enterprises. According to this standard, ERP is a Level 4 system, focused on business logistics, while MES, as a pillar of Manufacturing Operations Management (MOM) software, is a Level 3 manufacturing operations system. ERP software, then, provides business related functions needed to manage a manufacturing operation, while MES software orchestrates workflow operations needed to produce the desired end products.

ERP and MES systems complement each other in terms of their different functional purposes and points of focus, as well as the context in which their data supports the manufacturing endeavour. An ERP system brings together business strategy and operations, while MOM software, including MES, enforces and executes the manufacturing plans and bridges enterprise level ERP information to the automation and control systems on the manufacturing floor.

It should be noted that ERP and MOM systems (including MES) represent two of the three key functional hubs within a manufacturing company’s data infrastructure. The third is product lifecycle management (PLM), an ISA-95 Level 4 system, which focuses on product creation and engineering data.

But how do the differences between ERP and MES systems enable them to work together and bring the greatest benefits to a manufacturing floor? ERP software manages the business of manufacturing, often over a time horizon ranging from hours to years. The ERP integrates and acts as a data pathway for all parts of the business, from purchasing and inventory to finances and human resources. An ERP system gives decision makers a single point of access to pertinent information from disparate departments.

As it relates to production execution, an ERP system mostly addresses pre-production issues as well as post-production analysis. These may include product strategy, reference product information, production demand, master data, Bills of Materials (BOMs), Standard Operating Procedures (SOPs), change orders, as well as inventories.

Much of an ERP’s functionality is prompted by financial transactions, such as sales orders, supplier invoices, or payroll. Functions of the MES, on the other hand, are prompted by production orders and manufacturing processes. The MES orchestrates actual production in ‘real time’. It oversees and proactively enforces ‘live’ operations and performance and its functions generally focus on much more immediate time frames than the ERP.

MES functions include monitoring, controlling and adjusting variables that impact production efficiency, as well as synchronising various aspects of production to ensure lean operations. To perform these functions effectively, the MES must have the capacity to anticipate, align and adjust production and business parameters in ‘real time’.

Data shared between ERP and MES systems flows in both directions – the ERP system collects and/or generates information that serves as input to the MES, and as production operations take place, the MES gathers and generates information and sends it back upstream to the ERP. As the business hub, the ERP system interacts with departments and systems across the enterprise. It aggregates and contextualises data, then distributes it as needed to departments for use in their functional responsibilities.

An ERP system’s production related data is needed as input for the MES to coordinate production operations. This is the first aspect of the relationship between the two systems. ERP data feeds downstream to MES. The MES software receives and regroups this information to focus on manufacturing decisions, such as which plant or production line to use, which operators have the qualifications and availability to run production tasks, and where and when to deliver raw materials and supplied components to the production line.

The second aspect of the ERP and MES relationship flows in the opposite direction – with data from the MES providing the ERP with input for the many business operations that the ERP manages. For example, the ERP may route information about an operational bottleneck to the finance department, where decisions about capital equipment investments are made. MES may also share material consumption, scrap or completion information with the ERP to track costing and inventory.

Manufacturing companies that successfully integrate their ERP and MES systems stand to reap numerous benefits, including increased overall equipment efficiency, reduced cycle times and data entry, data consistency, as well as leaner manufacturing. Siemens has designed Opcenter Execution MES systems to interact effectively and efficiently with ERP systems to maximise production efficiencies and minimise time to delivery.