What is a manufacturing execution system
A manufacturing execution system (MES) is software that tracks and controls production on the shop floor in real time: it receives the work order from the ERP, tells each work center what to run, records what actually happened, and sends the result back to the ERP.
It sits between planning (ERP) and the equipment (PLCs, sensors). The ERP knows what was sold and bought; the MES knows, minute by minute, what the line is doing, why it stopped and how many good parts came out.
MES visual map
The map shows the ERP, MES and shop-floor pyramid, the data flow between levels and the OEE example used in this article.
Where the MES fits: the ISA-95 pyramid
The ISA-95 standard (IEC 62264) organizes enterprise-to-control integration into levels. The MES sits at level 3, manufacturing operations management.
| Level | What it is | Examples |
|---|---|---|
| 4 | Business planning | ERP, sales, purchasing, costing |
| 3 | Manufacturing operations | MES, detailed scheduling, quality, traceability |
| 2 | Supervision and control | SCADA, HMI |
| 1 | Direct control | PLCs, drives, sensors |
| 0 | Physical process | Machines, line, operator |
Levels 4 and 3 work on different horizons: the ERP plans in days and weeks (see MRP and the master production schedule); the MES works by shift, order and operation.
MES functions
The 1997 MESA International model lists 11 functions. In practice they group into six blocks:
- Detailed scheduling and dispatching: order sequence per machine and release to the station. It complements production planning and control.
- Data collection and reporting: quantity, scrap, setup time, labor hours and downtime, by automatic reading or terminal.
- Resource and labor management: status of machines and tooling, operator qualifications.
- Quality and process control: inspections, deviation alerts, lot hold.
- Traceability and genealogy: which raw-material lot, machine and operator produced each part.
- Performance analysis and maintenance: OEE, productivity and maintenance requests.
No company needs all of them at once. Most start with reporting and downtime, which already feeds OEE and the andon.
MES and ERP integration
| Direction | Data exchanged |
|---|---|
| ERP to MES | Production orders, quantities and dates, bill of materials, routing, priorities |
| MES to ERP | Good and scrapped quantity, actual material consumption, machine and labor hours, order status |
The gain is in the second direction. Without an MES, the ERP receives late, hand-keyed confirmations, and actual cost and inventory lag. With it, production cost comes from measured data, not estimates.
Example: OEE calculated from MES data
Illustrative example: a machining line with a planned shift of 480 min. The MES logged 60 min of downtime, an ideal cycle time of 30 s (0.5 min) per part, 700 parts produced and 679 good.
| Item | Calculation | Result |
|---|---|---|
| Run time | 480 − 60 | 420 min |
| Availability | 420 ÷ 480 | 87.5% |
| Performance | (700 × 0.5) ÷ 420 | 83.3% |
| Quality | 679 ÷ 700 | 97.0% |
| OEE | 0.875 × 0.833 × 0.97 | 70.7% |
Check: 679 good parts × 0.5 min = 339.5 min of fully productive time, and 339.5 ÷ 480 = 70.7%. The MES earns its keep on the input data: with manual logging, the 60 min of downtime is usually under-reported and OEE looks better than it is.
How to implement it in 6 steps
- Define the problem: late reporting, no traceability, downtime with no recorded cause.
- Map the flow and the data of the line, as in value stream mapping.
- Pick a pilot: one line or cell with a known bottleneck.
- Integrate: ERP (orders and confirmations) and machines (counters and states).
- Standardize downtime and scrap codes before go-live.
- Train, use it in the daily meeting, and only then expand to other lines.
The MES is the shop-floor data backbone of Industry 4.0, but it does not replace a well-defined process.
Common mistakes
- Buying the system before standardizing the process and downtime codes.
- Keeping manual reporting in parallel, doubling the operator's work.
- Rolling out every function and every line at once.
- Integrating with the ERP without deciding who owns each data item.
- Measuring without acting: data that never reaches the daily meeting drives no improvement.
Frequently asked questions
What does MES stand for?
Manufacturing Execution System. It controls and records production in real time.
What is the difference between MES and ERP?
The ERP plans resources and the business (orders, inventory, cost). The MES executes and records what happens in production, by order, machine and shift.
Does an MES replace production planning?
No. Planning plans; the MES executes, collects data and allows rescheduling with real information.
Which ISA-95 level is the MES?
Level 3, between the ERP (level 4) and supervision and control (levels 2 and 1).
Does every plant need an MES?
No. With few machines, a spreadsheet and a board may be enough. An MES pays off with many orders, required traceability, or manual reporting that delays decisions.
Does the MES calculate OEE?
Yes, when it collects downtime, part counts and scrap. It is one of the first applications.
Sources
- ANSI/ISA-95 / IEC 62264. Enterprise-Control System Integration.
- MESA International. MES Functionalities and MRP to MES Data Flows (white paper), 1997.
- KLETTI, J. (Ed.). Manufacturing Execution Systems: MES. Berlin: Springer, 2007.
- NAKAJIMA, S. Introduction to TPM. Cambridge: Productivity Press, 1988.
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About the author
Lean Manufacturing & Behavioral Management Specialist
Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.
