Downtime & OEE Ledger

How to read this sheet

Fleet OEE is fully productive time over planned time across the register, which is the only formulation that survives machines of different sizes; the averaged figure is shown beside it because that is what most dashboards report and the gap is the point. The three fleet factors are derived so that they multiply back to the headline - averaging the per-machine performances instead would produce three numbers whose product is not the OEE printed above them, which is how a report comes to disagree with itself. Planned time is scheduled time, not calendar time: a machine deliberately idle for want of orders does not belong in the register, or availability reports a commercial decision as a breakdown. Downtime entered above the planned time is clamped to it rather than allowed to drive a negative availability through every fleet figure, and good output above total output is clamped the same way. The log is deliberately NOT reconciled against the register: they are two independently recorded numbers, and the residue between them is stoppage nobody wrote down. A negative residue means the log records more downtime than the machines do, which is equally worth knowing and usually means an event was booked against a machine that was not scheduled. Ideal rate is the machine nameplate rate for the product actually being run, not the fastest product it has ever made; using the latter moves the loss out of performance and into a place no improvement plan can reach it. The prize at target holds the current product mix and the current quality rate constant, so it is the output the same floor would yield at a better OEE and not a forecast of what a project will deliver.