What Is MES? Seeing Everything That Happens on the Shop Floor

What is ERP missing? Sales knows. Accounting has recorded it. Planning made a forecast. But on the shop floor, nobody knows how far the work order actually traveled. This gap is filled by MES.

Silent Shop Floor

Picture a customer. Monday morning, they send a fax: “100 pieces to this drawing, must be done Friday 5 PM.” The sales engineer takes the customer’s recipe, enters it into the ERP. “Cost is 8,000 TL, 5 hours of labor.” The planner opens a work order. The operator receives it.

Then silence.

Friday 3 PM. Customer calls: “Have you shipped? If not, when will it be ready?” The planner checks the screen. ERP says: “In Production.” When will it finish? No idea. How many pieces are done, 50 or all 100? No information. The planner calls the floor: “Hey, where is this work order?” The operator says: “We started this morning, machine broke at 11, didn’t have a spare tool, waited two hours. After lunch we got going. Right now we’ve done about 70, but 10 came out bad, need to re-run them. Won’t finish Friday morning.”

Shock. But what do you tell the customer? The sales engineer calls Friday morning: “It’s delayed.” Customer is upset. But why the delay? Broken machine? Slow operator? Bad recipe? Faulty design?

No answer. Just “it happens.”

MES Opening Scene

Now play the same scenario in a shop with MES.

Monday 8 AM. Work order IE-5847 opens. When the operator picks up the card, the system automatically logs start time = 08:15. Before the operator starts the machine, they read digital instructions: “100 pieces, 5mm hole, note: customer wants special point location” — this comes from Engineering directly, not on paper, digital. Setup begins.

Machine calibration runs: 08:15 to 09:00. MES logs: “setup time = 45 minutes.” The system also learns — in past records for this product, average setup was 40 minutes, this time 45. Why? The operator can note: “This customer’s hole spacing is tight, requires careful setup.” The system records this note.

At 09:00, seconds before production, the system wants to see a start signal — either the operator presses a button, or a sensor auto-detects it. Which option depends on the shop’s setup. First piece start time: 09:00.

100 pieces. 20 pieces per hour. Expected time: 5 hours.

09:00-10:30: 30 pieces done. System: “pace is good, on schedule.” Lunch break starts.

12:00-13:00: Production continues. 20 more pieces (total 50). System: “on track.”

13:00-13:45: Sudden stop. Machine sensor detects something — abnormal vibration from the spindle. Operator leaves the machine and calls maintenance. MES logs: “unplanned downtime started at 13:00, reason = vibration alert.”

13:45-14:15: Maintenance arrives. “Found looseness in the spindle coupling. 30 minutes to fix. Machine re-calibrated.” MES captured this automatically. System: “downtime duration = 45 minutes (13:00-13:45 diagnosis, 13:45-14:15 repair), cause = loose spindle joint.”

14:15: Machine restarts. But the operator runs 3 witness pieces first to verify. The system logs how many pass. All 3 good. System: “quality check = 3 samples, all good.”

14:18-15:00: Series continues. 50 pieces left. But around 14:50, the operator notices “this piece feels different.” Pulls it out, production doesn’t stop but the bad piece is logged in MES: “defect at 14:50, reason noted = tool edge wear.” System: “1 piece scrap, total defect count = 1.”

15:00: Remaining 46 pieces done. Rewind: from 09:00 to 15:00 is 6 hours, but actual production time = 5 hours (excluding stops), repair and quality time = 1 hour, total clock = 6 hours.

Work order closes automatically. MES report:

• Target: 100 pieces
• Completed: 99 pieces (1 scrap)
• Actual production time: 5 hours
• Setup: 45 minutes
• Unplanned downtime: 45 minutes (machine)
• Quality checks: 3 (all passed)
• Defect rate: 1%

Friday 2:30 PM. Customer calls: “Status?” The planner opens the MES screen. Directly visible: IE-5847, started Monday 09:00, finished Friday 15:00, 99 pieces passed quality, completed despite 1 scrap. Can tell customer: “Shipping Friday 4 PM, we’re including the replacement.”

Customer satisfied.

More importantly: if the shop runs this job 100 times, they no longer guess. They have real data.

Without MES?

It works. But outcomes:

• Blind shop floor. When will the job finish? Guess. Miss again. Reschedule.
• Machine breaks. Where? When? Why? Operator’s memory. No one can say “this machine has this problem with this part type” based on data.
• Quality. Defect rate is “gut feel.” Same problem, different shifts, different times — is it the same rate? Unknown.
• Cost accounting. Real labor hours: 4 or 6? ERP pays by 5-hour standard. Where’s the gap?

MES’s Boundary

MES exposes the shop. But it doesn’t fix design. Bad recipe? MES says “high defect rate”; it doesn’t cure the root. Sequence varies per customer? MES tracks it; doesn’t auto-reorder. Work order needs modification? MES records the change; doesn’t dynamically manage it.

Reordering operations, reallocating resources, dynamically applying quality standards — heavy work that MES alone can’t handle. Shop needs a layer above: MOM (Manufacturing Operations Management). We’ll talk about that tomorrow.

We continue exploring the layers that bridge the gap between ERP and the shop floor.