What is MES (Manufacturing Execution System)?

Robotic assembly line
Robotic assembly line

What is MES? (Manufacturing Execution System)

Manufacturing Execution Systems (MES) have been available on the market for quite some time now and for buyers at any stage of research, there are literally hundreds of MES options to consider.  As the term “MES” tends to cover a very broad range of capabilities, it’s unlikely to find any two solutions that will offer the exact scope of functionality. This is especially true within just the last few years, given the rapid progress of digital technologies related to “Smart Factory” or “Industrial Internet of Things” (IIOT) initiatives. It’s therefore crucial for you to understand the basic principles behind MES so that it can be put to work for your organization’s requirements, instead of the other way around.

The Best Approach to MES Systems

It’s been shown that the best approach to MES is to first determine the key business goals that you’d like to achieve, and then work backwards. This avoids endlessly wading through technical specs that describe a myriad of functionalities and can appear confusing until their exact context within the project is clarified.

In reality, some MES features and functions may be irrelevant for your immediate specific need, so this helps you take the guesswork out of the selection process. Of course these considerations will need to be noted for any potential future phases but we’ll get to that later.

Your goal in selecting an MES software (and the supporting hardware technologies) should be to create a plan towards a single platform that will meet your longer-term targeted objectives without any need for eventual replacement. The price of an MES system shouldn’t be calculated as simply the cost of the manufacturing execution system software and hardware, but rather the investment in the changes that a factory operation driven by MES will make, in order to allow the MES system to work effectively. Different MES systems will prescribe their own “best practices,” and the fundamentals of these practices should be compared to both your current and targeted operation. In most cases, the cost of change and the cost of ownership can be greater than the capital purchase itself.

MES & ERP Together

Once implemented at your facility, MES will work together with the other existing and future factory control systems. Most factories have an Enterprise Resource Planning (ERP) platform in place, which usually will appear to have some overlapping functionality with MES.  ERP however, is by no means an equivalent for MES, as it’s typically meant for logical planning for the factory, rather than handling the day-to-day physical operations that MES is designed for. An ERP system on its own doesn’t not have enough knowledge about individual manufacturing processes and capabilities, which creates the need for an intermediate process to “translate” the ERP data into something that can be executed; without MES, this is often done manually, which takes valuable time and resources.

With MES, information from ERP about requirements is gathered and used to build specific production operations that the MES platform will then manage. MES next provides highly-accurate and detailed, real time information about operations back to ERP, and this historical information can be queried and used to enhance the your planning capabilities for the next time around.

The powerful relationship between MES and ERP should be a key factor for consideration, especially, the point of exchange between the two systems. The simplest way to approach this area is to define and measure the roles of the two systems based on their strengths. In many factories, the planning is handled in a simple, logical way by ERP, while the more complex physical tasks that must take place in production are managed best by MES in a live and detailed environment.

Starting Out – The Value of MES Systems

When considering MES, your starting point should the endpoint of production, the completion of products that are ready for shipping. From the customer perspective, the most important metric here is on-time delivery. For the manufacturer, it’s the cost of building product as well as the capacity of the facility. Capacity here is defined and dictated not just by the range of equipment in place, but also how it’s used and managed when that inevitable time comes to change from one product model to another. When making a high mix of products, the flexibility of both your manual and automated production operations will dictate the overall effectiveness of your facility.

If you’re producing many different product types simultaneously, determining your overall capability to meet delivery goals can be a very difficult calculation. Here is the first real potential value of MES. Access to a computer-based digital factory model creates visibility into the status and performance of your processes at all times, and this presents countless opportunities for improvement in the flow of shop floor production and the assignment of work-orders. A cornerstone of MES is the live-time tracking of final products and sub-assemblies. Each production unit can be tracked on its journey through the factory with a unique ID with a label or an etched barcode.

The Benefits of A Simple MES Operation

At each key station, the unique ID of each production unit will be read, and this provides several key related values. First, MES processes information about each event, in this case showing the exact location of every production unit. Then, using the timings of each reading, MES will present a visualization of the flow of production units via graphs that show “Key Performance Indicators” (KPIs) that help both Production Management and Engineering understand the performance. For example, you’ll be able to identify “bottleneck processes” where products are queuing prior to a workstation. You can also find indications of “starvation of operations”, or situations where operators are idle as they wait for the next production unit to arrive. MES will display production units that fail test or inspection processes and need re-routing to repair stations as well as any disruptions that this is causing to the main production flow. Details about efficiency, productivity, Overall Equipment Efficiency (OEE) and more can all be determined by analyzing the throughput of production units through each production process and the travel time in between them.

Tracking production units like this leads to subsequent benefits. MES can ensure that when the ID of each product is read, conformance against the work-order is checked, so that each production unit will only go through each process in the proper sequence, including any repair loops. This enforces that none of your production processes, or more crucially, any test or inspection operations, are missed. Linking your MES systems with your engineering data preparation systems can also ensure that the appropriate operation standard and setup documentation for the operators will exactly match the product being manufactured, including any material substitutions or revision variations.

The ability to provide electronic documentation eliminates several risks that are often associated with paper-based document management, especially in the event of an audit situation, where regulatory compliance is key and revision control is EVERYTHING. Data from production processes, such as a test result, can also be collected and attributed to each production unit, creating an entire history of production in the form of production unit traceability. The level of complexity of this traceability will depend on how much data can be acquired from your factory’s machines and how much time is available for manual input from your operators.

A critical factor in the success of any new MES installation is machine connectivity and the quality of the system’s user-interfaces. Some clear differentiators of MES product capability are the ability to pull and interpret data from various different types of machines and the ability to consistently gather manual operator input in a controlled manner. MES interfaces are personal to the operator, and don’t need to be fixed to any operational location. Often there will be physical processes dedicated to certain products, such as with functional tests, so not all processes will need to be simultaneously manned.

This simple look from a “top level” of MES provides a fundamental visibility into the operation and valuable details about how it’s working, while also highlighting the areas where improvements can be made. However, there are many underlying factors that you need to consider to determine how you should approach any changes, and what corresponding effects those changes may have. Production has significant dependencies on other aspects of the overall factory operations as well. These dependencies include quality management, material preparation and logistics, engineering data preparation, and management of key tools and resources, including people.

The scope of MES spans deeper into the areas of factory management that include support for these dependent processes, so that you can address the root causes of any symptoms you see in the production flow, and optimize and improve the dependent processes themselves.

A Deeper Dive Into MES Systems

MES has many different meanings in terms of scope, what it includes, what it does not include etc. Most MES systems are created for maximum reach across industries, supporting various industry segments. In a few instances, some features may be irrelevant while in other instances they may be critical. Others are critical. There may never be a universal standardization of MES, defining what it must contain or what it is expected to include. The Industrial Internet of Things (IIoT) and other technological advances constantly evolve, changing the discussion around this matter. Current expectations for MES are to lessen the amount of operator support required and also to decrease interruptions and delays for data acquisition and process control by connecting bi-directionally with automated equipment. In order to gain visibility and control of possible disruptions during final assembly production, MES should provide the single digital platform to connect these different areas.

Factory Dependencies

Production processes are often designed to focus on the main production schedule delivering completed products to customers. The notion is that any interruption in the production schedule would jeopardize the on-time delivery performance, and this should never happen. If these interruptions were to occur, they would result in diminished productivity and risk the possibility of late completion, which would increase the cost for the operation by requiring excess finished goods stock. Final production completely relies on everything being prepared perfectly ahead of time, preferably on a “Just In Time” (JIT) basis such that it is available when needed- and not any time prior. Key dependency considerations to keep in mind include material preparation, engineering data, management of key tools and resources, as well as people. MES tracks both the current and planned production as well as up-to-date production progress. The order for material provisions and resource utilization can then be predicted, which enables MES to manage these resources to be in line with the final production requirements. MES can also fine-tune the final production schedule if resource capabilities are being exceeded. Therefore, MES operates in a live environment working in multiple areas at the same time and with many varying types of data, basically in a “big data” environment. The design and scope of the software determine how much value and range MES provides. Basic examples will calculate and determine requirements needed, then monitor performance progress. More advanced MES systems will manage significant attributes of the dependent areas, improving the benefits regarding automation, management and traceability.

MES Internal Supply-Chain Management

In order for production to be successful materials are critical. The absence of even insignificant part such as the correct cable or resistor, which in themselves have minimal cost, can impede production completion and perhaps should not even be started. Therefore, MES needs to treat every individual material as critical. ERP tracks materials simply by part number and quantity “on-site”, beginning from arrival of the raw material through to work-order completion, which is basically multiplying the products made, by the material counts in the Bill of Materials (BOM). Many ERP systems support material inventory by location however this is unreliable, due to it requiring extensive manual material counting and data entry at busy times. Almost always, the ERP view of materials is different from the physical situation, due to spoilage and other unaccounted losses. These inaccuracies and inability to locate materials when needed result in the need to adjust the ERP causing frequent, costly, and disruptive stock-checks. A basic MES system helps to provide the knowledge of materials movements, though the ERP system will continue to frequently make bad planning decisions based on incorrect assumptions of available material, which risks creating schedules that are unattainable. Advanced MES systems will fully control materials. This begins with materials being identified uniquely, either individually for essential components and sub-assemblies, or by carrier for bulk materials such as reels of SMT parts in electronics manufacturing. MES will then create and manage logistics tasks for materials operators by allocating storage locations and then dispersing materials throughout the factory, including warehouses, local stock areas and delivery to consumption locations. Mobile terminals scan materials in and out of locations and are a great way to have MES functionality wherever needed. Kanban, and JIT delivery are Lean principles which are the best principles to drive material movement requirements and are based on the predicted need for materials at the point of consumption. MES has complete visibility of the current and near-term intended schedule and provides live feedback about progress from the production processes by knowing the quantity of each material required for production. More advanced MES systems will also collect spoilage data and consumption data, that can then maintain near-perfect material inventory control and when shared back to ERP can improve the decisions made by ERP. Advanced facets of materials, such as storage environment requirements, baking cycles for moisture sensitive materials, obsolete and expired, and substitute materials against the approved BOM can also be managed by more advanced MES systems.

“Internal” material shortages are eliminated by MES technologies ensuring that a lack of materials never causes a disruption in production. A 75% reduction in bloated stock inventories a 30% reduction in material logistics, a 50% reduction in warehouse space and other savings for example related to production space and number of carriers required (such as feeders for SMT materials) are some additional benefits. The purchase of an advanced MES system for many can be justified by the potential savings in material related costs alone.

Engineering Data Management

Displaying electronic documentation at production processes is one task of a modern MES solution. As more processes become automated, such documentation is steered towards the setup of the process, while the automation follows a designated set of instructions. Software provided by the machine vendor usually formats and optimizes these instructions. However, the design of the product and local BOM provide the engineering data in which the instructions are derived. Dependent upon process capabilities and throughput metrics MES engineering systems divide the conversion of design and BOM data, and assignment of work to complete a product between the numerous automated and manual processes. Without such an MES tool, an engineer has to read in design data from several different formats, confirm data consistency, adjust the data depending on local BOM changes, and then manually divide the data out to the various production systems based on their experience and knowledge. In the case of complex manufacturing like electronics, this process can usually take several days. Unfortunately, this process essentially has engineering deciding the production configuration with which to make each product in advance, with very little flexibility. In today’s dynamic high-mix environment, this process is not sustainable. Digital product-models created by leveraging advanced MES systems takes data in electronic format from design and BOM, which automatically converts and assigns work based on engineering preferences, taking minutes instead of days. Depending on the actual condition of production and demand at the time, the ability to efficiently generate process data on demand enables the MES planning function to decide which is the best configuration to use for each product. Considerable improvement in asset utilization and productivity is a result of more adaptable planning. Lead times throughout the product hierarchy of sub-assemblies, optimizing execution considering all available configurations, changeover times, as well as product grouping strategies will be taken into consideration by The MES planning function. This Lean approach to planning is performed in hours or days not weeks or months. This amount of flexibility provides a step-change in the modern factory’s ability to respond to changes in customer demand, being able to smoothly make changes across a high-mix of products, all while keeping the highest utilization without producing excess finished goods stock. This practice can return a production improvement anywhere between 20% and 50%. This fixes the conventional problem of sharply declining productivity while product mix increases, leading to increased costs and investment which exists without MES, or with only a basic MES.

Reasons to Adopt MES System

In this last segment we finish by looking further into the levels of MES functionality that enables final production to work effectively. We then explore different types of MES Systems and review the important aspects of MES Systems to keep in mind when first implementing or when upgrading a basic MES that is already in place to a system with the latest IIoT digitalized technology.

An MES system is primarily focused on the ability to follow the planned production progress and associated activities, and to be able to adjust that plan to show changes in customer demand, available material and process capability. Depending on the package, MES Systems provide modules to aid these activities, to varying levels. Some include advanced control and optimization incorporating all the parts of supporting operation management. Now that we have explored material and engineering data management, we will now examine how MES controls other resources and dependencies.

Resource Management

There are various kinds of resources that are essential in any specific production process to operate properly. If any one of those resources are missing, then the process is unable to be performed. Basic examples include tools for assembly, such as simple screwdrivers or clippers. Processes may also need an array of specific support devices to be employed, for instance material feeders on an SMT machine. In this example, feeders must be prepared, created and installed to support the specific material that they will feed. Any mistake would be disastrous as it is a crucial process. This is why there is a great need for MES to include feeder preparation. Other Manufacturing Execution System use case examples include properly setting, calibrating and checking test equipment or torque-drivers that need to be set to a certain value prior to use. In many situations, it is the maintenance of the dependent device not just its presence and readiness. Most of the time when it comes to maintenance, where duty cycles are counted and managed causing routine maintenance it is necessary to manage the dependent resources current state in addition to managing the availability and setup. A more comprehensive MES will provide all of these tasks.

People As A Resource

The human worker is one of the most difficult resources to manage. Each person has unique skill sets, abilities and experience, such that they may or may not be capable of working on specific production processes. The ability to make or successfully complete production targets, or to even begin production at all in some  circumstances is greatly affected by break-times and instances of illness, vacations etc. It is crucial to know that operators with the necessary skillsets will be available at the exact moment that each production job is run. Advanced MES systems can provide additional, more innovative benefits. The demand for specialized operator skills can be reduced by the more operational know-how and guidance that is included in both the MES system as well as the process automation software. Operators can, move from one role to another within the team rapidly and safely to significantly improve production flexibility in this environment with the latest electronic documentation. This scenario would benefit by using mobile terminals, associated with the operator wherever the resource is required.

Active Quality Management

Any issues connected to quality are always disruptive to production. Additional unnecessary inspections, repairs, re-work and re-test cycles that cause delays and costs can be incurred by any defects that take place. Even more severe, whenever a defect is discovered, it is unlikely to be unique. There is a high probability of recurring defects happening until some counter-measure is identified and implemented. In some cases, this is so severe that it is better to stop production until at least the cause of the defect is known. In addition to managing the routing exception, MES collects electronic repair tickets from test and inspection processes, that assists analyzing defects and repair procedures. MES systems record both material and process events which minimizes the disruption of production through the fastest possible defect analysis supported by the complete and specific production history of the defective unit. Statistics can help determine the unique set of circumstances that caused this defect to occur, and, identify any other production units that have been made in the same way. MES systems provide complete traceability information for compliance and conformance for every production unit, guaranteeing through management of dependencies that everything needed is correctly in place, configured, and set up properly. In this way, an advanced MES delivers active quality management both within the factory as well as for products out in the market which aids in assuring the lowest cost of poor quality.

Maintenance Management

Experiencing equipment breakdown is another critical problem for manufacturing. To help avoid these unforeseen events, routine maintenance must be performed to all critical equipment. It is challenging however to know what maintenance jobs must be carried out and how frequently. The loss of production time may possibly be incurred as a result of performing simple time-based maintenance programs.  If, for example, the machine or line had not been used as much as anticipated many of these may be done unnecessarily.  By utilizing information about the accumulated work performed by each key production process MES can make a valuable impact to create a more sophisticated maintenance strategy. Preventative maintenance programs are designed that reduce maintenance to just perform only what is essential. This approach can be used on major maintenance jobs such as motor replacement in addition to regular maintenance tasks such as cleaning and lubrication. MES manages maintenance resources and organizes the timing of maintenance jobs, for example, at times that the machine is not being used for some other reason, or, the tasks will be included in the overall planning activity. MES maintenance terminals are innately mobile, which make them an important tool for the maintenance engineer, which provides interaction with MES that denotes the location and type of maintenance work, document adjustments and settings, and assist in understanding maintenance job procedures.

Breadth of MES Options and Platform Choices

The breadth and depth of MES systems available today are somewhat diverse. It is possible however to group MES applications into categories at a high level. One type is the simpler more generic MES systems, which are targeted to support numerous industries has basic functionality and is limited in scope regarding flexibility or customization. Even though these systems basically just automate the current production operation as far as the application supports, they can be useful. Another type of MES, is the complete opposite offering deep support of complex requirements, usually in a specific niche industry, and quite frequently need extensive customizations. this type of MES system can drastically increase costs as additional software customizations are needed, as well as on-going support costs. Something in between these extremes is the “sweet spot” ideal range of MES solutions. Utilizing well-known digital technologies which include the most current IoT standards a modern MES system, enables data collection from a variety of automated processes conceivable with minimal cost of ownership in terms of operator support. The modules follow standard digital process modeling and will offer relatively deep detail into key areas, with very little customizations required. These high quality MES systems are very configurable, offer the benefit of providing “best practice” methods in the way that production and engineering and other processes work and how they all work together. The outcome is the most modern and technically advanced MES solutions in manufacturing playing a vital role to realize the original business goals planned, with a clearly understood and attainable ROI, which in some cases delivers pay-back on investment in an almost astonishingly short time, sometimes, in just a few weeks.


When considering the implementation of MES systems or upgrading a legacy system to one of the latest more advanced systems there are many starting points to keep in mind. A great place to start is the success of business-related operational goals, but also be aware that multiple modules of MES may be useful in getting started. Conversely, introducing too many modules can cause disruption and increases initial cost. When evaluating MES, additional potential phases should be taken into consideration to ensure that once the selected MES platform is in place it can support future needs without having to consider replacement. A Return on Investment (ROI) analysis should be completed at each stage for every module, or group of modules to be considered. The potential effect of the changes on the benefits side, as a result of implementing MES, should be assessed. Depending on whether, capacity is the major concern, on-time delivery metrics, quality or conformance requirements etc. these assessments vary from one manufacturing operation to another.  Additionally, considering intangible factors is required.

The recommendation is to select an MES system that provide standard connections to all kinds of automation in addition to digital product and standard process modelling. This removes unnecessary expenditures and expensive customization.  Another element that will keep MES installation easy and cost effective is knowing the shop-floor hardware requirements, especially for human operated processes where operators may constantly rotate from one role or position to another.