Improve Phase: Solution Design, Lean Tools, and Pilot Testing
What the exam tests
Improve tests solution design and Lean countermeasures: generating and prioritizing solutions, piloting, mistake-proofing, setup reduction, pull systems, standard work, and DOE basics.
Core rules
- Link every solution to a verified root cause; otherwise you are adding work without removing the defect.
- Prioritize with impact/effort analysis or a weighted matrix, then pilot the highest-value change with a defined success metric, duration, sample, and decision rule.
- Poka-yoke prevents errors at the source; it is stronger than a warning or a retraining program.
- SMED separates internal setup (machine stopped) from external setup (machine running) and converts internal to external.
- Kanban is a pull signal that limits work in process; it is not a scheduling system that pushes work into the line.
- DOE screens many factors with a designed experiment; change one factor at a time only when the process is simple and interactions are unlikely.
Worked example
A changeover takes 96 minutes, with 70 minutes internal and 26 minutes external. Teams convert 40 minutes of internal work to external work, so internal becomes 30 minutes and external becomes 66 minutes. If external work is done while the machine runs, downtime falls from 96 to 30 minutes, a 69% reduction. The reasoning is that only internal time consumes capacity; the external work still has to be done, but it no longer stops the machine.
Traps
Piloting without a baseline or decision rule; changing many factors at once without a design; choosing training as the only countermeasure for a system-induced error; and claiming SMED savings without checking whether external work can actually run in parallel.