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Jeff Liker

Jeff Liker: All Companies Need Problem Solving Tools Based On Deming’s PDCA

By Jeff Liker, - Last updated: Sunday, April 4, 2010 - Save & Share - Leave a comment

The relationship between lean and six sigma  is one of my favorite topics….Not!  It is fitting that this question came at Easter time which is famous for the Easter egg hunt.  Let’s assume that lean eggs are red ones and  six sigma eggs are blue ones.  If you gather only the red eggs you will have an imbalance.  It will allow you to gather the eggs very quickly and efficiently but the red eggs are all different sizes and therefore there is a lot of variation.  On the other hand the blue eggs are very uniform so gathering some of them will reduce variation.  Once we get bored with only red and blue eggs we can go hunting for other colors, like those green eggs that are sustainable or those yellow eggs that are constraints that break as you pick them up.  Now we have a basket of many colors of eggs to admire, though those nasty yellow constraint eggs are all broken.

Back to lean and six sigma.  There is a convenient omission from this terminology.  No place in the discussion is the word system.  There is the Toyota Production System.  W. Edwards Deming was a systems thinker.  Let’s take TPS which was represented as a house with pillars.  There is just-in-time–the red eggs that allow us to do the work efficiently with minimum lead time.  There is jidoka–kind of like the blue eggs because it really deals with eliminating variation.  There are many tools, like TPM, standardized work, 5S that allow us to break constraints–sort of yellow eggs.  There are key performance indicators to focus kaizen efforts and that can ultimately relate to an entire management system of hoshin kanri.  Maybe that is a new colored egg.  And then there is rigorous, root-cause problem solving that is kind of like six sigma–a blue egg with a different shade.  Sustainable is becoming a key performance indicator, is facilitated by just-in-time, can become part of the standardized work, etc. so not sure where that fits.  In other words the more TPS becomes a total system the more it subsumes all the colored eggs and adds some more.

Seriously, if we look at the history of TPS it evolved at first piece by piece, and then grew as an increasingly elaborate socio-technical system.  Just-in-time was a vision of Kiichiro Toyoda, but as Ohno evolved TPS over decades he kept adding stuff.  He also discovered that JIT was a great driver for quality, safety, productivity.  Without inventory problems get exposed immediately and you solve them one by one, if you have a good problem solving methodology and people doing the work are expert on how to use it.  Stopping production is a way of focusing attention on the problems.  Standardized work is how you stabilize the process to allow one-piece flow, but also gives you a standard to check against when you uncover a problem.   In the 1960s Toyota discovered Total Quality Management which included hoshin kanri.  It was the introduction of TQM that allowed them to harness the energy of all employees toward superior quality and landed them the Deming prize.

Flash forward to 2010 and go into Toyota and say:  “Akio, you have been doing lean for all these years.  Now you have recall problems.  I would like to introduce you to six sigma.”   That would make no sense.  They have all the tools they need to solve the problem in the Toyota Way.  They need to get out to where the customers are through genchi genbutsu, which they are doing with the new SMART teams.  They need to identify problems in ways like this immediately and then get them to the right people to use their rigorous Toyota Business Practices to solve the problems one by one.  Ultimately they need to elevate respect for people and continuous improvement to a new level.  Introducing new words like six sigma or a black belt program will not help them.

Now we can rephrase the question as follows:    If a company that does not have a history of process improvement has started with lean and used lean tools to work on flow issues, setting up cells and supermarkets, will this be enough?  The answer is a resounding no.  All they have done is set the stage for identifying problems.  They need a problem solving method.  Some companies are using six sigma in this way and that is fine.  The serious ones learn that the green belt training given to the work groups will solve the large majority of problems.  But then you still need to evolve over time into other aspects of the system–team leader role, andon, standardized work, visual management, hoshin kanri, etc.  I say evolve because it is a long-term process in which you try something, make mistakes, reflect, adjust, and then as you get good at that you add more to begin to build a system.  The underlying framework was also taught by Deming and it is PDCA.

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