Advanced manufacturing requires the proper planning of resources, quality management, effective use of tools on the shop floor, management of equipment and human schedules, and quick responses to interruptions and unplanned events. Enterprise Resource Planning systems (ERPs) are specifically designed to manage company-wide resources, scheduling, and supply chain requirements and interruptions. Most advanced manufacturing environments either employ or use to some degree ERP systems to orchestrate the many moving parts in order to compete on a global scale.

To a large extent, ERPs lack the granularity required to put the right materials at the right time in front of the right tool in a dynamic and complex production line. Stated differently, ERPs are effective in the context of a high-level, organizational role in an enterprise. An additional layer needs to be integrated into the “smart factory” to produce the material requested in a timely, controlled, safe, and predictable manner. This layer needs to not only be responsible for the actual manufacturing of the material, but also responsible for collecting, storing, and making data available regarding the actual manufacturing process, provide granular visibility of the steps in the process, and consistently enforce the same process requirements repeatedly until intentionally changed. This additional layer is called the Manufacturing Execution System (MES).

Automation Pyramid MES

What is an MES?

The Manufacturing Enterprise Solutions Association (MESA) defines an MES as the following:

“A Manufacturing Execution System (MES) is a dynamic information system that drives effective execution of manufacturing operations. Using current and accurate data, MES guides, triggers and reports on plant activities as events occur. The MES set of functions manages production operations from point of order release into manufacturing to point of product delivery into finished goods. MES provides mission critical information about production activities to others across the organization and supply chain via bi-directional communication.” 1

Admittedly, that definition is a little abstract, so let’s pursue a more concrete understanding using an everyday example. In order to successfully bake a cake, ingredients need to be procured, the right supplies need to be available, and customized requirements need to be addressed (which may require more or different supplies) and the “due-date” needs to be determined. These are examples of elements handled by resource planning. When resource planning is finished, the table is littered with these related but disconnected items, so how do all of the raw materials come together to make a cake? This is where the execution system takes over with a recipe, ordered steps, cook times, and acceptable alternatives if some ingredients are not available or the cake needs to be optimized at the request of the end-consume.

The MES at the Core

Architecturally, the MES exists between the ERP systems on the enterprise side and the tool-level control systems on the other. MESs facilitate the free-flow of information from the MES to the ERP and from the MES to the automation systems. Whereas an ERP system communicates with other systems globally, the MES is more factory-focused in managing processes, ordered steps, process flows, and equipment. ERP and MES systems (and, to a lesser degree, equipment automation systems) must work together seamlessly; one system’s output becomes another system’s input, and together, the manufacturing process becomes more scalable, predictable, reliable, and visible.

Manufacturing Execution System Integration

MES applications come in many shapes and sizes. Some MESs are home-grown applications while others are off-the-shelf applications. Some are industry-specific while others are generic. Some are text-based while others present all the graphical goodness of a modern UI. Some require local installation while others run in the cloud. In some cases, it may be difficult to differentiate between the MES and ERP components because of the integration of these domains into a monolithic, one-application-approach to smart manufacturing (this is not a bad thing!), while other implementations contain three very distinct and well-defined applications in the ERP, MES, and automation domains. Beyond these structural and graphical differences lie the core requirements and purposes of an MES.

Manufacturing Execution System

MES Core Components

The MES can answer the following questions:

  • How to produce?
  • What can be produced?
  • When and what should be produced?
  • When and what was produced? 2

To answer these questions, MESs implement and manage the following core components:

  • Enumerated steps – a step is an atomic value-added activity on work in progress that, when connected sequentially with other atomic steps in sequence, creates a finished sellable product. These steps are often enumerated numerically, although some MESs may permit alphanumeric conventions.
  • Process flow control – the above-enumerated steps are placed in sequence resulting in a defined and reusable process flow. MESs excel at managing process flows regardless of whether they are just a few steps or whether they are multiple process flows chained together encompassing thousands of steps.
  • Product definition – a product can be defined by a single process flow or a series of process flows chained together resulting in a finished product. Product definitions can also contain metadata which provides further granularity and classification of the product. MESs help to define products in both high- and low-product-mix environments. Versioning and product options are both visible to the end customer and transparent to the floor operators as process changes are programatically “activated” using metadata in the product definition.
  • Equipment assignment – a process step is often attached to a tool or tool type. Therefore, when the material reaches a given process step, the MES knows what equipment is required for that process step. Some tools in a tool group may be better equipped to process a specific product. MESs may also be able to track a product to a tool that is running in a way that satisfies or optimizes the product’s requirements, thereby increasing quality and customer satisfaction.
  • Real-time control – sometimes work in progress needs to be paused or stopped in the course of processing in order to further investigate or collect data. MESs allow for these pauses in support of any ancillary activity, including R&D of new products as well as optimizations of current products. These pauses can be real-time (at the current step) or future pauses at upcoming steps in the process flow.
  • State logging – similar to flow control on work in progress, state logging identifies the availability of equipment to process work that arrives at the equipment station.
  • Genealogy – each step completed in the process produces the next sentence in the story of the material being processed. Even after the material is shipped, its genealogy is available for review and further study in pursuit of process improvements or other uses.
  • Regulatory Compliance – the components above serve as data points to support regulatory compliance requirements. Whether you are producing appliances, medications, microprocessors, vehicles, or component widgets, every industry has some level of compliance and certification required to produce parts for that industry. In many cases, component level tracking contributes to improved quality assurance statements and metrics, making an MES a necessity for a vast array of manufacturing certification.

For the past 30 years, SYSTEMA has been at the center of smart manufacturing as a requirement (rather than a dream). Our experiences show us that the MES boundaries and capabilities listed above are becoming increasingly blurred as both MES and ERP systems have succumbed to “feature creep” in an effort to become a single monolithic application for smart manufacturing. Thankfully, our experience has also shown that both MES and ERP applications can be customized at the component level to blend the best of both worlds into a complementary, co-existing, seemingly seamless application that helps plan, manage, and track manufacturing activities.


With an MES in place, KPIs, performance data, and future intelligent planning begins to become available. Cycle time (the time between steps), critical ratio (the measurement of how far a lot is ahead of or behind schedule), equipment metrics pursuant to SEMI-E10 standards, OEE, and a host of other indicators may be available within the MES or at the very least the data is available for query and extraction into business intelligence software. The MES makes it possible to collect, control, store, and report this information. To that end, the MES is best-positioned as a “first step” action in any factory’s digital transformation. The MES will grow in scope and complexity as a factory’s systems and automated processes mature and will serve as the foundation for most every other step in the digital transformation journey.


1 What is MES?: A & D Tech Eng. (n.d.). Retrieved December 2, 2019, from

2 Siemens. (2008). Manufacturing EnterpriseManufacturing Enterprise.