Manual vs automatic OEE tracking in the first week

When you stop writing stops on paper and let the machine report them, your availability drops and your performance rises to match. The short stops, rounded durations and shift-start gaps the paper missed were already in your OEE, hidden as slow running. OEE itself moves only if your part counts, ideal cycle times or planned production time were wrong, and the first week is when you find out.

The sections below work one shift both ways, list the inputs that do change OEE and give a five-day plan for the switch. They’re written for plant managers who need the new numbers believed on the floor.

Manual and automatic tracking defined#

OEE multiplies three factors. Availability is run time over planned production time, performance is ideal cycle time × total count over run time, and quality is good count over total count.^[1] The OEE glossary entry gives the same factors in IoTFlows’ terms.

Neither method changes the formula. They change who records each input and when, as the figure shows.

Why the stop log can’t change OEE#

Multiply the three factors and run time cancels out. It sits in the numerator of availability and the denominator of performance, so what’s left is a ratio with no stops in it:

This is the single most useful fact for the first week. Every stop the machine finds that the paper missed takes minutes from run time. Availability falls, performance rises by the same factor, and OEE stays where it was.

Availability fell 12.9 points and nothing on the floor changed. If you report availability on its own, warn the team before the first shift report goes out. For each factor worked step by step, see how to calculate OEE.

Where the missing minutes come from#

The paper log in the example held 35 of the 93 stopped minutes. The other 58 came from three places, and each one has its own fix.

• Short stops. A minor stop is one that lasts a minute or two and needs no maintenance technician, and most companies don’t track them accurately.^[2] Here, 24 jams and clears cost 36 minutes nobody wrote down.
• Rounded durations. An operator writes the stop when it’s over, from memory, in round numbers that run short. The 27-minute material wait became 20 and the 18-minute freeze-off became 15.
• Shift edges. The warm-up and the restart after the handover rarely reach the sheet, because the machine never “broke”. Here they cost 12 minutes.

The split between availability and performance depends on a cutoff. One published example policy gives every stop longer than 2 minutes a reason, which files it under availability; shorter stops stay in performance.^[2] Pick a cutoff, write it down and keep it, so the same jam lands in the same factor every week. For how short stops behave and how to cut them, see micro-stops.

What does change OEE in the first week?#

OEE moves only when an input in the formula above changes. The first week of machine data tests each one, and most plants find at least one that was off.

Quality is the factor automation helps least. A molding machine runs the same cycle for a short shot as for a good part, so someone at the machine or an inspection step decides which parts were scrap.

The ideal cycle time causes the largest surprises. It should be the best cycle the operation sustains in good conditions, so performance above 100% means the ideal is set too slow.^[1]

The paper record hid the error, because unlogged stops padded run time and pulled performance under 100%. The machine record exposed it on day one.

Manual and automatic capture compared#

Each method records the same inputs with different precision. The difference is widest for stops and counts, and nil for scrap.

Use paper when you’re proving the habit on one machine for two or three weeks, before you spend anything. Use machine-reported data once you need short stops, more than one machine or numbers during the shift.

Automatic capture still needs your definitions#

Switching the capture method doesn’t fix the inputs people set. A study from Chalmers University of Technology shows what happens when nobody does.

The researchers analyzed six months of data from 23 Swedish manufacturers and 884 machines, all running the same automatic OEE system.^[3] Median OEE was 70% and the average 65%.^[3]

• Performance at the default. 702 of the 884 machines reported 100% performance, the system’s default value, which suggests no cycle times were measured.^[3]
• Quality at the default. 796 of the 884 machines reported 100% quality, also the default.^[3]
• Losses with no reason. Unclassified losses took about 19% of scheduled production time, more than half of all recorded loss time.^[3]

With performance and quality left at their defaults, the authors question whether those companies measured OEE at all, or only availability.^[3] Their conclusion: when measurement is automated, managing the details of each process matters more, not less.^[3]

Three tasks in your first week prevent each of these failures: set an ideal cycle time per operation, log scrap at the machine, and give every unexplained stop a reason. A short reason list gets used; see which downtime reason codes to log.

A five-day plan for the switch#

Run the paper log and the machine record side by side for one week on the machines you switch first. Paper stays the reference for reasons and scrap; the machine becomes the reference for minutes and counts.

1. Define shifts and breaks before day one

   Enter the plant’s timezone, shifts and scheduled breaks so planned production time matches the floor. Shifts sort data as it arrives, so set them before the first machine reports; see shifts and timezone.

2. Check the count against ten parts

   On day one, count ten parts by hand as they come off and compare them with the machine’s count. A four-cavity mold set to one part per cycle reads a quarter of its real output; the ten-part check says how close is close enough.

3. Correct each ideal cycle time

   On day two, check performance for each operation. Performance above 100% means the ideal cycle time is set too slow, so enter a faster one; see set the ideal cycle time.

4. Classify routine stops by rule

   On day three, set rules that classify short stops and stops at the shift edges, so operators explain only the stops in the middle of a shift. Automatic downtime rules covers each one.

5. Log scrap at the machine

   From day three, operators log each bad part when it happens, with a reason, instead of tallying the bin at shift end. The scrap logging steps show the entry.

6. Reconcile the week factor by factor

   On day five, put the paper and machine figures side by side for each shift. Explain the stopped-minute gap by source: short stops, rounding, shift edges and offline time. Reconcile with a manual calculation lists the differences that remain.

After day five, retire the paper log and mark the switch date on every trend chart. Set the first goal a few points above the new baseline, never the old paper figure; choose an OEE goal explains why.

Track OEE from the machine#

A SenseAi sensor mounts magnetically on the outside of each machine and detects every stop in seconds, with no PLC connection and no operator input. IoTFlows reports OEE factor by factor: availability as uptime, performance as parts counted against the ideal cycle time, and quality from the scrap operators log with a reason. Data lands in the shifts you define as it arrives.

The Short Downtimes rule classifies stops under a per-machine cutoff, 5 minutes by default, and the shift-start and shift-end rules cover the edges. Operators put a reason on what’s left in a tap.

Sorinex installed SenseAi sensors across its critical production equipment in under 5 days, and its story reports an 87% improvement in root cause visibility within the first month.

When manual tracking is enough#

Choose manual tracking when:

• You track one machine for a few weeks to prove the habit before spending anything.
• Your stops are long and rare, such as a machine that runs a 6-hour cycle and stops twice a shift.
• You haven’t set ideal cycle times yet, since performance means nothing without them on either method.

Choose automatic tracking when:

• Short stops are frequent, because no operator can write down 24 jams in a shift.
• You run more than one machine or shift, and the numbers need to match from one to the next.
• You need the numbers during the shift, while there is still time to recover the loss.

Whichever you choose, fix the inputs first. A correct count, an honest ideal cycle time and a trusted shift schedule matter more to your OEE than the method that records the stops.