What Is Manufacturing Execution System (MES)?
Also known as: MES, shop floor execution system
Definition
A Manufacturing Execution System (MES) is software that tracks, controls and documents production on the shop floor in real time, from releasing a work order to recording what was actually made, by whom, on which machine and with which materials.
Manufacturing Execution System (MES) Explained
An MES sits between the ERP, which plans what should be made, and the machines and operators, who actually make it. The ERP knows the order, the routing and the bill of materials. The MES knows what is happening right now: which operation is running, which lot of material was consumed, what the measured values were, and whether the operator followed the instructions.
Typical MES functions include dispatching work to work centers, collecting labor and machine time, enforcing electronic work instructions, recording quality checks, tracking lot and serial genealogy, and reporting downtime and scrap. The functional scope is described in the ISA-95 model and by industry bodies such as MESA.
Many ERPs ship with a lighter built-in layer. Infor SyteLine has shop floor transactions, Job Order Transactions and the Shop Floor Data Collection (SFDC) module. Infor LN has Shop Floor Control. NetSuite relies on Work Orders and a Manufacturing Mobile or partner MES for terminal-level detail. A standalone MES is added when the ERP layer cannot enforce routing steps, capture machine data or meet traceability rules.
Why It Matters
- ERP data is only as good as shop floor reporting. An MES makes reporting automatic and timely instead of end-of-shift paperwork.
- It closes the gap between planned and actual cost by capturing real labor, machine time and material use per job.
- Regulated and aerospace shops need as-built records, operator sign-off and genealogy that an ERP alone rarely provides.
- It exposes live status to planners and AI assistants, so answers about order progress are based on facts rather than stale schedules.
In Practice
A machine shop runs 40 jobs a day. Without an MES, operators write start and stop times on travelers and a clerk keys them at the end of the shift, so WIP shows yesterday's position. With an MES terminal at each cell, the operator scans the job, the system checks that the previous operation is complete, shows the current drawing revision, and posts quantity and scrap to the ERP as each operation finishes. A planner asking where job 4412 is gets an answer within seconds.
Frequently Asked Questions
What is the difference between MES and ERP?
ERP plans and accounts for the business: orders, inventory, purchasing, costing and finance. MES executes and records what happens on the floor in real time. The ERP says what to build; the MES controls and documents how it is built and reports the actuals back.
Do I need an MES if my ERP has shop floor transactions?
Not always. If operators can report quantities and time accurately in the ERP and you have no strict traceability or work instruction needs, the ERP layer may be enough. An MES pays off when you need enforced routing, machine data, electronic records or lot and serial genealogy.
Can an MES run on-premise?
Yes. Many MES products deploy on-premise, and plants in defense, aerospace and electronics often require it so production data and drawings stay inside the facility network.
Related Terms
Work Order
A work order is the ERP document that authorizes production of a defined quantity of an item by a due date. It snapshots the bill of materials and routing, drives material issues and labor reporting, and collects actual cost for the job.
WIP (Work in Process)
WIP (Work in Process) is inventory that has been released to production and has begun conversion but is not yet a finished good. It includes partially machined parts, subassemblies, and material sitting in queue between operations.
Traceability
Traceability is the ability to follow the history, location, and application of a part or material through the supply chain and production process, both backward to its sources and forward to every product and customer it reached.
OEE (Overall Equipment Effectiveness)
OEE (Overall Equipment Effectiveness) is a manufacturing metric that multiplies Availability, Performance, and Quality into a single percentage showing how much of scheduled production time an asset spends making good parts at its rated speed.
ISA-95 (IEC 62264)
ISA-95 (also IEC 62264) is the international standard that defines how enterprise systems such as ERP exchange information with manufacturing operations systems such as MES and plant control systems, using common models for equipment, material, personnel and activities.
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