Planned (preventive) maintenance is work on a machine scheduled in advance: lubrication, filter replacement, hydraulics checks, calibration. The goal is to maintain the machine before it breaks down, not after.
Why it is outside OEE
OEE measures how well the planned production time is used. If maintenance is scheduled in advance, that time is not planned for production — just like a break or a meeting. That is why planned maintenance does not lower OEE.
This is deliberate. If every minute of maintenance pulled OEE down, managers would have a reason to postpone it — and the machine would later fail unplanned, at the worst moment.
An overrun is a loss
The rule applies only to the plan. If a check is scheduled for 60 minutes and takes 95, those extra 35 minutes are a loss of availability and count toward OEE. This way:
- maintenance is protected when it is planned and correctly estimated;
- a poor estimate or lack of preparation (no part, no tool) shows up as a loss;
- nobody can “hide” a breakdown by calling it maintenance.
Example
Press PR-04 has a service scheduled on Saturday, 08:00–09:00. The technician starts on time, but the oil filter is not in the warehouse — the service ends at 09:40.
- 08:00–09:00: Planned maintenance, outside OEE.
- 09:00–09:40: Maintenance · overrun, 40 minutes of availability loss.
In next month’s Pareto of losses, “overrun” may show that the problem is not the machine but the stock of parts.
How often
The starting point is the manufacturer’s manual. Later, the history tells you more: if the MTBF for the hydraulics is about 120 running hours, the check goes before that. It is good to count the interval in running hours or cycles, not only calendar days — a machine running three shifts wears faster than one running a single shift.
In MachineTakt
The Maintenance module keeps a schedule of preventive tasks per machine, work orders and parts used. The “Planned maintenance” stop is outside OEE, and “Maintenance · overrun” is an availability loss — both are system stops and cannot be switched off.