MES Explained: Real-Time Shop Floor Data
In earlier posts, we saw how information fragments across paper, Excel, the master operator’s memory, and WhatsApp groups. We then discovered that ERP doesn’t solve this problem because ERP is built to record financial and procurement transactions, not to track what happens on the shop floor moment by moment. So what fills that gap?
The answer: MES.
What is MES?
MES — Manufacturing Execution System — is the manufacturing management layer that sits between the shop floor and everything else. ERP records that an order was created. MES records when the order opened in production, when it closed, and everything that happened in between.
What happens between order open and order close? Each operation starts and stops. Each operation may pause or resume. Each operation has actual duration and theoretical duration. The difference costs money. There is scrap, rework, defects. There are downtime events: machine failure, power outage, operator break.
MES tracks all of it. When did the operation start? When did it finish, and how long did it take? If it paused, why? For how long? Did it resume?
Most of the time, the operator or shift lead doesn’t use the system moment by moment. Either they clock an operation in when it starts and clock it out when it ends, or they enter all operations at the end of the shift. Either way, the rule is the same: the system records the data, and reports show it.
Documentation matters, but here is what really matters: we make decisions based on MES data. If Operation A takes 45 minutes on average instead of the planned 20 minutes, why is that? Is the operator under-trained? Is the equipment worn? Is the recipe too tight? MES doesn’t answer those diagnostic questions by itself, but it establishes the hard fact: this operation takes 45 minutes.
A Concrete Scenario: Order 248
Order 248 is a custom metal control panel. The work order opened. The operations are:
- Sheet cutting (10 minutes planned)
- Welding work (30 minutes planned)
- Fastening and assembly (15 minutes planned)
- Painting (20 minutes planned)
Total planned: 75 minutes.
The work order opened at 09:00. In theory, it should close by 10:15.
Without MES, what happens? At 17:00, the shift lead enters all operations one by one: cutting started 09:00, finished 09:15. Welding started, but… was there a breakdown? Where did the operator go? Did someone restart it after 12:00? Ask different people, get different answers. Because it was in someone’s head.
With MES: The operator touches a button at 09:00 when cutting starts. Touches another button at 09:18 when it ends. The system records: cutting took 18 minutes (8 minutes over the planned 10). Why? Was the material too thick? Did the cutter need sharpening?
When that data flows into the reports, planning sees it. They say, “Cutting always takes 8 minutes longer than we expect. We need to account for that in our estimates.” Or: “Cutting was normal this month, but last month we were running 15 minutes slow. Did we service the equipment this month?”
Without MES, nobody looks at these numbers. Everyone knows the shift report was hand-entered Friday evening and is probably wrong. With MES, the data is trustworthy.
Why ERP Alone Isn’t Enough
Can ERP do this? In a limited sense, yes. You can manually enter when operations start and stop into ERP. But ERP cannot flow continuous data like MES does. ERP is built for sales and accounting, not for real-time shop floor tracking.
Also, entering every operation start and stop into ERP is overkill. MES picks up the data from the floor itself—from the machine, the workstation, the operator’s input—as the work flows. A button press, a scan, an input device. That’s it.
The Bottom Line
MES fills the gap that made-to-order manufacturers feel every day. It addresses the fragmentation of information and the blindness of ERP-only systems. What you need is to get to a state where you can say, “we trust this data.” For MES, that is the first milestone.
In the next post, we’ll look at MOM: MES, plus a wider layer of coordination for production, quality, maintenance, and inventory.