Mean Time Between Failures (MTBF) and Mean Time to Repair (MTTR) are the two fundamental metrics for equipment reliability and maintenance effectiveness. MTBF measures how long a machine typically runs before failing — higher is better. MTTR measures how quickly the maintenance team can diagnose and fix a failure — lower is better. Together, they determine equipment availability: MTBF / (MTBF + MTTR).
MTBF is improved by preventive maintenance, operator care (autonomous maintenance), design improvements, and environmental controls. MTTR is improved by technician training, spare parts availability, diagnostic tools, and standardized repair procedures. Most manufacturers focus on reducing MTTR first because the improvements are faster and less capital-intensive.
Tracking MTBF and MTTR by machine, failure mode, and component reveals where maintenance resources should be concentrated. A machine with low MTBF needs reliability improvements; a machine with high MTTR needs better repair procedures or spare parts stocking. This data-driven approach to maintenance investment replaces the common "squeaky wheel" allocation that sends resources to whoever complains loudest.