Planned downtime is scheduled and accounted for: changeovers, preventive maintenance, breaks. Unplanned downtime is the surprise: breakdowns, quality stops, material shortages, missing operators. Both matter, but they are managed differently, planned downtime is minimized through SMED and TPM; unplanned downtime is attacked through root cause analysis.
Every downtime event should be logged with start time, end time and reason. Over weeks, a Pareto of downtime reasons reveals the vital few causes responsible for the majority of lost time. Those causes become the priority for improvement. Without this data, downtime reduction becomes a firefight instead of a systematic program.
TPM (Total Productive Maintenance) addresses breakdowns through autonomous maintenance, planned maintenance and root cause analysis of every failure. SMED reduces changeover time. Poka-Yoke and Jidoka reduce quality-related stops. Kanban and pull systems reduce material shortages. Each lean tool ultimately shows up as less downtime and more productive time.
Downtime is one of the most visible symptoms of an unstable process. Measured honestly and attacked systematically, it is also one of the largest sources of quick-win capacity, often adding tens of percent of effective capacity without buying a single new machine.
