Lean and Six Sigma
March 31, 2004
Many of today’s articles, books, and seminars are
focusing on the power of combining Lean and Six Sigma.
Most of these take a Six Sigma perspective; that is, they
talk about adding lean tools to a Six Sigma program to make the
program more effective. I
believe such an approach can work; however, I believe that lean
should drive six sigma initiatives.
Furthermore, I believe that the tools of Six Sigma can be
effectively integrated into Lean without actually implementing a
“Six Sigma” program. While
this might be considered sacrilege to the Six Sigma faithful, there
are facts to support this assertion.
Firstly, let us consider Toyota.
The first word that people might think of when they think of
Toyota is “Quality.” Toyota’s
vehicles are consistently rated among the most reliable; customer
satisfaction is consistently very high.
Yet, Toyota does not have a Six Sigma program in place.
They use the Toyota Production System, or, as it is most
commonly called in the rest of the world, “Lean Manufacturing.”
Looking beyond Toyota, James Womack and Daniel Jones in the
book Lean Thinking performed a study on 50 companies that
have implemented Lean. After
an initial lean conversion, the companies averaged a 50% reduction
in errors reaching customers and a 50% reduction in scrap rate- all
without a single black belt!
How can this be done?
A lean program focuses on eliminating
non-value-creating activities or waste.
Value Stream Mapping is a powerful lean tool that identifies
waste and sources of waste.
Many times, Value Stream Mapping uncovers problems that cannot be
solved without reducing process variability.
Process variability is the reason for many of the seven
wastes; for example, it can be responsible for overproduction,
excess inventory, defects, overprocessing, etc.
In come cases, process variability cannot be reduced with a
simple fix such as a go/no-go fixture; the tools of Six Sigma (which
have been around for years) and the Six Sigma DMAIC methodology are
very effective in these cases.
This is where Six Sigma fits into lean.
The Black Belt/Green Belt system can work very effectively,
but it isn’t required for using the tools of Six Sigma.
Let’s take an example.
“B” Company produces machined components and assembles them
into widgets. “B” company has
4 manufacturing processes within its operation: Machine 1, Machine
2, Weld, and Assemble. After
mapping its value streams and creating a future state map, “B”
company discovers that it must make the following four improvements
to achieve its future state:
1. Increase Weld uptime (by implementing TPM, Total
Productive Maintenance).
3.
Reduce
the scrap rate on machines 1 and 2.
4. Eliminate the rework portion of its assembly
activity.
“B” company might find that it needs to apply the tools of Six Sigma to achieve the third and fourth improvements. It can do this in a variety of ways. If it has a true Six Sigma program in place, it can create two projects and assign a black belt and a team to each using the DMAIC methodology. If it doesn’t have a formal program in place, it can have a team perform exactly the same function as a Six Sigma team; they can also use DMAIC. Alternatively, they can assign an engineer to solve the problem using the very same tools; he may need to form a team, or, if the problem is not quite that complex, he may be able to solve it on his own with some input from others. As long as the problem is solved and the above initiatives can be implemented, success will have been achieved.
Some companies view Six
Sigma as their prevailing, culture-changing program and add lean
tools to their Six Sigma toolbox.
Others have lean as their program of emphasis with six sigma
tools as complimentary. I've
seen successes on both sides; however, I believe that Lean is the
most effective methodology when used by itself (while making use of
the statistical methods and problem solving tools of six sigma).
Many companies that have implemented lean (such as Toyota)
have superb quality without having implementing Six Sigma
specifically. However, it
should be noted that these companies do apply the statistical
methods of Six Sigma to improve their processes.
This has been going on long before the term "Six Sigma" as a
program was ever used.
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About the Author
Darren Dolcemascolo is an internationally recognized lecturer, author, and consultant. As Sr. Partner and co-founder of EMS Consulting Group, he specializes in productivity and quality improvement through lean manufacturing. Mr. Dolcemascolo has written the book Improving the Extended Value Stream: Lean for the Entire Supply Chain, published by Productivity Press in 2006. He has also been published in several manufacturing publications and has spoken at such venues as the Lean Management Solutions Conference, Outsourcing World Summit, Biophex, APICS, and ASQ. He has a BS in Industrial Engineering from Columbia University and an MBA with Graduate Honors from San Diego State University.
EMS Consulting Group helps companies implement lean strategies through lean training and lean consulting services. To learn more, read our lean manufacturing case studies or lean manufacturing articles.