Re-measure 2 weeks after any constraint fix
Two weeks after any constraint intervention, re-measure the old constraint and scan for queue buildup elsewhere; if the old constraint improved but total throughput did not improve proportionally, the constraint has shifted.
When This Fires
- Two weeks after any process improvement, tool upgrade, or workflow change
- When a local improvement didn't produce the expected overall results
- When Optimize only the single slowest step — improvements…'s bottleneck-first optimization needs the follow-up verification
- Complements Optimize only the single slowest step — improvements… (optimize only the bottleneck) with the post-optimization verification cycle
Common Failure Mode
Celebrate-and-forget: "We fixed the bottleneck!" without re-measuring. The old bottleneck improved, but the new bottleneck now limits throughput at the same rate. Total output is unchanged despite the intervention.
The Protocol
(1) After any constraint intervention, set a calendar reminder for 2 weeks. (2) At 2 weeks, measure: Old constraint metric (did it actually improve?), Total throughput (did overall output improve proportionally?), Queue scan (is work piling up at any new location?). (3) If old constraint improved AND total throughput improved proportionally → success. The intervention worked and no new constraint has emerged. (4) If old constraint improved BUT total throughput didn't → the constraint has shifted. Identify the new constraint (look for queue buildup) and redirect optimization there. (5) If old constraint didn't improve → the intervention didn't work. Diagnose why and try a different approach before moving on.