Plex Downtime Reason Log and OEE Worksheet
Whether your downtime is captured on Plex or on a clipboard, you need one place to see which reasons cost the most minutes and what OEE results. This worksheet logs each workcenter shift and computes the three OEE factors for you.
| Workcenter | Shift | Main downtime reason | Planned production minutes | Downtime minutes | Ideal parts per minute | Total parts | Good parts | Availability | Performance | Quality | OEE | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
86.7% | 86.5% | 97% | 72.8% | |||||||||
78.9% | 88% | 98% | 68.1% | |||||||||
91.1% | 93.5% | 97.8% | 83.3% | |||||||||
84.4% | 89.9% | 97.1% | 73.7% | |||||||||
93.3% | 95.2% | 98% | 87.1% |
OEE = Availability x Performance x Quality. Performance is capped at 100 percent so a wrong ideal rate cannot inflate the result. Use the planned production time your plant policy defines, and keep it consistent between lines.
Turn downtime data into a weekly summary
Optional: we can discuss an on-prem AI summary of downtime and OEE from your MES or ERP data.
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How to use the worksheet
Enter one row per workcenter per shift. Fill planned production minutes, total downtime minutes, the ideal rate in parts per minute from the routing or engineering standard, total parts made and good parts. Availability, performance, quality and OEE calculate automatically. Pick the main downtime reason so you can sort the exported sheet and total minutes by reason for a Pareto chart.
The OEE method
Availability is run time divided by planned time. Performance is actual output divided by what the ideal rate would have produced in the run time. Quality is good parts divided by total parts. Multiply the three. A line at 85 percent OEE is often cited as world-class for discrete manufacturing, but typical plants sit well below that and the right target depends on your process and how losses are defined, so compare to your own baseline first.
- Availability loses time to stops and changeovers.
- Performance loses speed to slow cycles and micro stops.
- Quality loses output to scrap and rework.
Reading the results
Look first at the lowest of the three factors for each workcenter: that is where improvement is cheapest. If availability is poor, sort downtime by reason and attack the top one or two. If performance is poor but availability is good, check ideal rates, because an unrealistic standard makes every shift look slow. Compare shifts on the same workcenter to separate process problems from staffing or material problems.
Common mistakes
Many plants count planned maintenance or no-demand time as downtime in one report and not in another, so OEE figures cannot be compared. Others use inconsistent ideal rates between systems, or include rework as good parts. Decide definitions once, write them down, and apply them across the Plex data and this sheet.
Frequently Asked Questions
Is this specific to Plex?
The calculation is standard OEE and works for any plant. It is labelled for Plex users because the columns match the data most Plex MES teams already collect: workcenter, shift, downtime reason, counts and scrap.
How do I choose the ideal rate?
Use the engineered or demonstrated best cycle time for the part on that workcenter, converted to parts per minute. Avoid using the average actual rate, since that hides performance losses.
What if I run several parts in a shift?
Use one row per part run or use a weighted ideal rate for the shift. The simplest approach is one row per part and shift, then average the OEE or recompute it from summed minutes and parts.
Should changeover count as downtime?
In standard OEE it is a stop loss and reduces availability. Some plants track it separately for SMED work. Whatever you choose, keep it consistent.
Netray can build dashboards or AI summaries on top of your MES and ERP downtime data so the weekly review no longer depends on manual spreadsheets.
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