Lean improvement and process reengineering solve different problems, and the symptoms look similar from the outside.
Improvement fits when
- The process design is sound but execution varies
- Waste is visible: waiting, motion, defects, over-processing
- People can describe the intended flow
- Results improve when the team focuses on the same metrics
Reengineering fits when
- The process was designed for a business half the current size
- Handoffs exist for organisational, not customer, reasons
- Cycle time is dominated by approvals and queueing
- Different sites do the same job differently
The test
Map the process end to end and count handoffs. If more than half the elapsed time is waiting between steps, improvement will shave the steps but leave the waiting. That is a design problem — reengineer, then improve.
Why this matters commercially
Improvement programmes rarely fail technically; they fail because they optimise a process the business should not be running at all. Getting the diagnosis right is most of the value.