The Bathtub Curve & Why Preventive Maintenance Alone Guarantees Failure
Traditional PM assumes machines wear out linearly like car tires. Historical United Airlines and Nowlan & Heap data prove only 11% of equipment follows the bathtub curve.
1. The Shopfloor Reality of Hidden Losses
In standard accounting and maintenance logs, equipment uptime is heavily distorted by batch rounding.
Nakajima proved that chronic micro-stoppages (sub-5 minutes) account for up to 3x more cumulative capacity loss than major equipment breakdowns.
Modern high-speed lines cannot be managed using retrospective shift summaries. Real-time telemetry must isolate speed loss, idling, and minor jams instantly.
RCM & TPM consensus: Time-based overhaul often introduces more infant defects than it prevents.
2. Root Cause Elimination Protocol
To eliminate chronic stoppages, plants must adopt a standard 3-tier countermeasure process.
Tier 1: Restore basic equipment conditions through disciplined cleaning-as-inspection.
Tier 2: Maintain operating standards by eliminating contamination at the generation source.
Tier 3: Conduct PM Analysis on recurrent failures to eliminate chronic losses permanently.
Gemba SOP: Chronic Micro-Stop Elimination Protocol
Log every stoppage under 3 minutes using one-touch digital loss buttons.
Inspect transfer rails, chute angles, and optical switches for physical wear.