MES and ERP integration: patterns, standards and pitfalls
· 5 min read · By YLinkTech
MES and ERP integration connects the system that plans the business with the system that runs the plant, so orders flow down and production results flow back without retyping. It works when you agree which system owns each data object, define each exchange using a shared model such as ISA-95, and pick an integration pattern that fits how often the data changes. Most failed projects skip the first two steps and go straight to interfaces.
Why the two systems are hard to connect
An ERP system and a manufacturing execution system (MES) describe the same factory at different resolutions.
- Time. ERP plans in days and shifts. An MES records events by the minute or second.
- Granularity. ERP sees a production order and a quantity. An MES sees each operation, lot, serial number, machine and operator.
- Purpose. ERP answers what to make and what it cost. An MES answers how it is being made right now and whether it meets specification.
Integration is the work of translating between those two views without losing meaning. A quantity confirmed in the MES has to become the right inventory and cost postings in ERP, and a changed order in ERP has to reach the line before the wrong material is consumed.
What ISA-95 gives you
ISA-95, published by the International Society of Automation and also known as ANSI/ISA-95 or IEC 62264, is the main reference for this boundary. ISA describes it as an abstract model for exchanging information between manufacturing control functions and business functions. It is technology neutral. It defines activities and information, not products or protocols.
The standard arranges a manufacturing enterprise into five levels:
- Level 0: the physical production process.
- Level 1: sensing and manipulating the process, through sensors, valves and similar devices.
- Level 2: monitoring and supervisory control, including PLCs and distributed control systems.
- Level 3: manufacturing operations management, where the MES sits.
- Level 4: business planning and logistics, where ERP sits.
ISA states that the standard primarily deals with the interface between levels 3 and 4. It has eight parts. Part 1 sets out models and terminology, and its current ANSI/ISA edition is dated 2025. Part 2 specifies the objects and attributes exchanged across the level 3 to level 4 interface. Part 3 models the activities of manufacturing operations management. Part 5 defines business-to-manufacturing transactions, and Part 6 describes a messaging service model.
ISA-95 is a model, so you still need a concrete format. B2MML, maintained by MESA International, is a set of XML schemas that implement the ISA-95 data models, and a JSON version is published alongside it. Below the MES, OPC UA, released by the OPC Foundation in 2008, is a platform-independent, service-oriented architecture often used to bring machine data up to level 3 with built-in security and information modeling.
You do not have to adopt every part. Even using only the level definitions and vocabulary gives IT and operations staff the same words for the same things, which ISA names as one of the standard’s purposes.
Four MES and ERP integration patterns compared
| Pattern | How it works | Fits when | Watch for |
|---|---|---|---|
| File or database exchange | One system writes files or staging tables, the other reads them on a schedule | Volumes are low, changes are infrequent, a legacy system has no API | Delays between batches, silent failures, and direct table access that breaks on upgrade |
| Point-to-point API | MES and ERP call each other’s published interfaces directly | One plant, one MES, one ERP, and a small number of exchanges | Tight coupling. Each new plant or system multiplies the connections |
| Middleware with a canonical model | An integration layer maps both systems to a shared model, often based on ISA-95 objects | Several plants or MES products share one ERP, or systems are replaced at different times | The canonical model needs an owner and version control, or it drifts |
| Event-driven messaging | Systems publish events such as order released or operation completed to a broker, and others subscribe | You need near real-time status, many consumers, or analytics alongside transactions | Ordering, duplicates and replay must be designed in. Not every ERP transaction suits asynchronous delivery |
Many manufacturers end up with a mix: events for status and machine data, and synchronous calls for the few transactions where the plant needs an immediate answer. Whichever you choose, plan for the network link between plant and data center to fail. The MES should keep running and queue its messages until the link returns.
Decide which system owns each data object
Before designing any interface, agree the system of record for each object and write it down. A typical split looks like this, though yours may differ:
- Item and material master: ERP owns, MES receives.
- Bill of materials and routing: ERP owns the planning version. The MES may hold a more detailed execution version, so define how the two stay in step.
- Production orders: ERP creates and releases. The MES owns the detailed schedule and operation status.
- Material consumption and production confirmations: the MES records, ERP posts.
- Inventory: ERP owns balances by location. The MES owns work in progress and line-side stock, if you track it.
- Quality results, genealogy and traceability: the MES owns, and ERP receives the summary it needs for release and for customers.
- Labor and equipment time: the MES captures, ERP uses it for costing.
For each exchange, also record the trigger, the frequency, what happens on rejection, and who fixes a failed message.
Pitfalls that cause rework
- Unit and identifier mismatches. ERP counts in cases, the line counts in pieces. Material and equipment IDs differ between systems. Fix the mapping rules before testing.
- Order changes after release. Decide what the MES does when ERP changes quantity, date or components for an order already running.
- Confirmation timing. Posting every count to ERP in real time can flood it. Posting once per shift hides problems. Choose per object.
- No error ownership. Failed messages pile up unless a named team monitors and reprocesses them.
- Customizing both ends. Custom fields in ERP and in the MES to make them match will complicate every future upgrade. Put the translation in the integration layer.
- Testing only the normal path. Test scrap, rework, split lots, partial deliveries and reversals, because these are where postings go wrong.
If you are also weighing whether to buy an MES or extend what you have, the build vs buy framework applies. Clean, well-identified execution data is also the foundation for projects such as predictive maintenance.
How YLinkTech helps
YLinkTech designs and builds integrations between plant and business systems for manufacturing clients. Through our Digital Product Engineering practice, we map data ownership with your operations and IT teams, define the exchanges, and deliver the APIs and systems integration work, including monitoring and error handling. We work with the MES and ERP products you already run. To discuss your plants and systems, get in touch.
Frequently asked questions
What is the difference between MES and ERP?
ERP plans and accounts for the business: orders, purchasing, inventory balances, costing and finance. An MES manages execution on the shop floor: dispatching operations, recording what was made on which machine and lot, and capturing quality data. In the ISA-95 model, ERP sits at level 4 and the MES at level 3.
Is ISA-95 required for MES and ERP integration?
No. ISA-95 is a voluntary reference model, not a regulation or a product feature. Many teams use only its level definitions, vocabulary and object models to structure their interfaces. That shared language makes it easier for IT and operations to agree on scope and for integrations to survive a later change of MES or ERP.
What data is exchanged between MES and ERP?
Typically ERP sends item and material data, bills of materials, routings and released production orders to the MES. The MES sends back operation status, material consumption, quantities produced and scrapped, labor and machine time, and quality or traceability summaries. The exact list depends on which system you choose as the owner of each object.
Sources
- ISA: ISA-95 series of standards, Enterprise-Control System Integration
- MESA International: B2MML and BatchML repository
- OPC Foundation: OPC Unified Architecture
This article is general information, not professional advice. See our Disclaimer.