MTTR — Mean Time To Repair

MTTR (Mean Time To Repair) is the average time taken to restore a machine after failure: total repair time ÷ number of repairs, over a period.

Formula: MTTR = total downtime spent repairing ÷ number of breakdowns. If a lathe had 3 breakdowns costing 2h, 3h and 1h of repair, MTTR = 6h ÷ 3 = 2 hours.

The trap: most plants unknowingly include waiting time (for approval, for the technician, for parts) inside "repair time" — hiding whether the problem is the machine or the process. Split the clock: reported → approved → started → resolved.

Improving MTTR is usually about logistics, not spanners: parts availability, technician skill match, and knowledge of past fixes. A falling MTTR with a rising MTBF is the signature of a maturing maintenance function.