Foreword
I decided to write about this topic when I was told to
explain Lean Manufacturing methods, techniques and philosophy. Thinking about
the correct approach I realized it was not possible to think about Lean
Manufacturing without Six Sigma and other Problem Solving methodologies.
Therefore prior to talk about the merge of Lean
Manufacturing and Six Sigma that nowadays is yet occurring, I would like to
explain both concepts separately. Once we have a clear concept of each one then
the idea of merging them will become simple.
Lean Manufacturing
As most of you already may know, the first manufacturer that
applied Lean Manufacturing was Toyota some years later of the end of the Second
World War. At that moment all manufacturers were taking the advantage of the
pros of Mass Production, economies of scale advantages mainly.
As costumers requirements started to become more and more
restrictive, a new way of thinking turned out to be essential. More final quality
of goods, better productivity figures and lower costs were required, so Mass
Production did not gave new solutions to these new requirements.
Lean is based on the reduction of waste. Lean is not only
some techniques and methods, since the philosophy is as important as techniques
to not lose what Toyota calls the “true north”.
There are many words written about the seven or the eight
(lately one additional type of waste has been added to the list) components of
waste but not much about the “ideal” process. Everything is intended to go step
by step to this process called by some authors as “one piece process flow”.
Let’s imagine a process where costumer’s orders go directly to the queue of
orders, that is not ideally a queue since the takt time (demand) and cycle time
(real manufacturing process) are the same (perfect line balancing), and without
any waste the final product goes off the production line Just in the Time required
to process all the operations needed to finish the product, that is without delays,
scrap, inventory, etc…
This vision of an ideal process could be considered as part
of the philosophy of Lean or as it is sometimes called “Lean Thinking”.
To achieve this ideal state we would need to identify and
remove all kind of waste and to do so would also need motivated people and
empowered as well as a Continuous Improvement mindset. Continuous Improvement
is another important leg of Lean together with the People. I personally like to
explain Continuous Improvement using a concept from Physics, the idea is not
mine of course… I am talking about ENTROPY.
Entropy means transformation/evolution in Greek. The
universe has a natural tendency to evolve from an ordered state of the energy
to a chaotic state. This evolution is natural, not forced, and if you leave the
systems alone they will tend to behave in this way. So it is observable and
demonstrable that the whole universe is going from an ordered state to a more
chaotic one.
Entropy also applies to manufacturing processes very well.
If you ask any experienced Team Leader, Manager, etc., about what happens with
processes if you leave them alone once you have reached a certain level of
performance they will answer “they will go back to a lower performance level by
their own”, that’s entropy!
It becomes obvious that Continuous Improvement is not an
option, as we have only two options: IMPROVE or DECLINE.
PDCA (Plan, Do, Check, Act) is part of the philosophy
although could be also considered as a technique as due to its application we
setup real objectives and the Continuous Improvement thinking really works. So
Continuous Improvement would be the philosophy and PDCA cycle is the way to
reach it.
And
here we go one of the reasons of having Lean Metrics - another leg of Lean. We
need Lean metrics such as DTD, OEE, FTT, BTS, WIP, etc. They are not only due
to the fact that we have to measure to be sure that process performance is
improving, but also due to the implicit reason that we will never be working as
the ideal process is supposed to do, one piece flow, and therefore need to know
where we are and quantify the progress made.
The
other leg we need is how to get closer to the ideal process. We need
techniques and methods, Lean Manufacturing itself. They are intended to be as
closer as possible to the ideal process so we have to consider them as a tool
box and each expert has to decide which tool has to be applied to each process
and waste. These tools are 5S, Kanban, SMED, Poka Yoke, Yamazumi, Value Stream
Analysis, etc… Everything tied together with PDCA.
Only
as a clarification, 5S is the only one that is not optional. We need always to
implement 5S as the basics for Lean Manufacturing.
It
is convenient not to forget that PDCA is a scientific method used to tackle
processes and improve their performance. As all scientific methods need to be
based on data. Together with PDCA, a wide set of statistical tools were used to
Describe and Control processes. It is known that PDCA and SPC (Statistical
Process Control) were widely used by Edwards Deming, father of PDCA cycle.
So
now we have the complete picture of Lean Manufacturing, as we have the
philosophy, methods, techniques and scientific tools.
But
why do all this sometimes does not work?
Real
World is complex. Complexity means there are many of factors which can affect
the output. System thinking gives us this point of view. As the relationship
between inputs and process outputs is not obvious, we’d rather say, it is
complex, we need a tool to analyze and improve the real world to the extent we
need.
Moreover, thinking that only waste can affect process
performance is a simplification of the reality, as mentioned before. System
thinking gives us a more comprehensive approach to model processes as it says
that input settings, noise factors and transfer function of the process is what
gives us the final model.
It is true that just applying Lean Manufacturing we will
always obtain big results, but after that we will need to go deeper in the
understanding of the whole system to obtain even better results (a 4-sigma
process has a level of defects of 32 defects per million, a 6-sigma process has
much less defects, it can be considered as a defect-free process).
That’s
why in the late 90’s and at beginning of 21st Century 6 Sigma
appears in the scene. It is a methodology which includes everything. Six Sigma
has the best from Lean Manufacturing as the first thing to do in a 6-Sigma
project is applying Lean Tools where needed.
SIX SIGMA
DMAIC (6 Sigma process, Define, Measure, Analyze, Improve
and Control) has a clear connection to PDCA, uses a wide range of statistical
tools, to extent that in most companies 6 Sigma Master Black Belts are
considered as statistical experts in their companies, includes many tools and
techniques of Lean Manufacturing and has a clear systemic approach.
We
could say that Six Sigma is not another method for problem solving- it is the
method. It can be applied to either manufacturing process or transactional
ones. Even it is applicable not only to an existing process but also to processes
in the Design Phases with a slight change of the method called DFSS – Design
For Six Sigma which applies DCOV phases (Define, Characterize, Optimize and
Validate).
Six-Sigma
is not an artificial invention. It is the natural result of a history of scientific
methods applied to industrial processes performance improvement.
The
first thing a Black Belt has to do is to Define the issue, mapping the process
(Value Stream Mapping) and then setting up a Baseline Performance Level and a
Goal (an affordable one). Nothing new, Kaizen philosophy PDCA is based on the
same approach.
As
Lean is based on Waste Identification and removal, Six Sigma deals with
defects. A defect can be defined as a traditional quality defect or in a more
general concept the state of your output when not meeting costumer
(internal/external) expectations (Voice of Costumer- VoC), also called error
state of the output.
Can
you imagine a process with no waste and any defect? That would be a process
that always exceeds costumer expectations and uses the minimum resources to do
it. That is what Six Sigma does when is well applied together with Lean
Manufacturing.
Not
by chance, lately Six Sigma is being called worldwide “Lean Six Sigma”, what is not a different thing, is just the
same with its correct name.
