Key facts
- Origins: Six Sigma was developed at Motorola in the 1980s; lean manufacturing comes from the Toyota Production System. The combined name became common in the early 2000s.
- Goal: faster, more predictable processes with fewer defects.
- Method: DMAIC projects, typically lasting two to six months.
- Roles: yellow, green and black belts, with a sponsor who owns the process.
How do lean and Six Sigma fit together?
Lean asks where time and effort are wasted: waiting, rework, excess stock and movement. Six Sigma asks why the output varies, and the name refers to a process capable of about 3.4 defects per million opportunities. A slow process with stable quality needs lean; a fast process that makes scrap needs Six Sigma. Most real problems need both, which is why the two are taught together.
What are the Lean Six Sigma belts?
| Belt | Typical training | Role |
|---|---|---|
| Yellow belt | One to three days | Knows the basics and supports projects in their area |
| Green belt | One to two weeks | Leads projects part-time alongside their normal job |
| Black belt | About four weeks plus a project | Leads complex projects full-time and coaches green belts |
| Master black belt | Years of black belt experience | Runs the programme and trains black belts |
No single body sets the standard; training providers and certifiers such as ASQ and IASSC each define their own.
Which tools does Lean Six Sigma use?
Lean tools include 5S, standard work, SMED and kanban. Six Sigma tools include SIPOC maps, measurement system analysis, Pareto charts, fishbone diagrams, hypothesis tests and control charts.
When is Lean Six Sigma the right choice?
Use it when a measure stays red despite daily countermeasures, the cause is not obvious and data can be collected. For everyday problems, PDCA or 5 whys is faster. The common failure is a belt programme that runs apart from daily work: projects finish, the control phase has no owner and the gain fades. Keep the project's measure on the tier board so the team sees whether it holds.