Where the planned time went
Each row is a share of planned production time. Availability loss is stop time. Performance loss is time spent running below the ideal rate. Quality loss is the time spent making units that were rejected.
Downtime Pareto
By line
By week
What the checks found
The checks look for gaps in the record. They cannot tell whether the counts, the ideal rate or the stop reasons are true. A second person has to check those against the line.
The sums
- Planned production time: the minutes the line was meant to run, after planned breaks. You enter it for each run.
- Run time = planned time minus the minutes of every stop you recorded.
- Availability = run time divided by planned time.
- Performance = the time the units made should have taken at the ideal rate, divided by run time.
- Quality = good units divided by all units made.
- OEE = availability times performance times quality. It is the same as the time spent making good units at the ideal rate, divided by planned time.
- Totals across runs add up the minutes and units first and then divide. They are not an average of each run's percentage, which would give a short or slow run the same weight as a full one.
The ideal rate decides everything
Performance and OEE depend on the ideal rate you enter, in units per hour. If it is set low, performance looks good. If it differs from line to line or year to year, the OEE figures cannot be compared. Write down where the ideal rate came from (design rate, best demonstrated rate, or the standard time) and keep it the same. The tool does not decide it for you. A common target such as 85 percent is only a talking point. It means nothing unless the ideal rate and the stop rules are defined the same way.
What the checks do
- A run with a missing date, line, planned time, ideal rate or counts is listed and left out of the OEE figures.
- A run whose stops add up to more than the planned time, or with more good units than units made, is impossible and is left out.
- A run with performance over 100 percent is left out. It means the ideal rate is too low, the count is wrong, or stops were not recorded.
- A stop with no reason is counted in the Pareto as "Reason not recorded", and a gap is raised if that is over 20 percent of downtime.
- Each run needs a person who recorded it and a different person who checked it.
- Two runs for the same date, line and shift are flagged as a possible duplicate.
Reading the Pareto
The Pareto ranks stop reasons by minutes lost. The cumulative line shows how much of the total the top reasons make up. It only counts stops somebody recorded. Short stops of a minute or two are often not written down, so the real minor stoppage loss is usually bigger than it looks, and shows up as performance loss rather than as a stop. Use it to choose what to investigate next, for example with the 5 Whys tool or the Causal Tree Builder, then track the fix in the Corrective Action Tracker.
Limits
No gaps found does not mean the figures are right. OEE describes the line, not the people on it. Do not use it to rank or judge individuals. This is decision support only.