What really keeps performance from slipping back? Mike Rother of the University of Michigan, and Jeff Uitenbroek from Modine Manufacturing Company suggest that the “wedge” of standardization that we’re taught will keep improvement from rolling back is a mistaken idea. They suggest that a standard is more like a target condition, and that the only way to maintain gains is to keep improvement moving forward. This is an issue Jeff and Mike feel the Lean community should now be talking about, and the AME LinkedIn group has first crack at discussing it. Comment here or go to LinkedIn groups and search for Association for Manufacturing Excellence.

1. F O RS I O N
S
D I SCU
Let’s Retire the PDCA Wedge
What really keeps performance from slipping back?
Mike Rother
Jeff Uitenbroek
August 2011
nt
roveme
Imp
Wedge indicating
standard or
standardization
to hold gains
Mike Rother RETIRE THE PDCA WEDGE? 1

2. SOMETHING TO THINK ABOUT
Dear Lean Community,
We may have a bug in our programming, which is hampering our
efforts to achieve continuous improvement.
The PDCA wedge may be a creation of an occasional-improvement
mindset, which allows for backsliding between events, instead of
a mindset of continually improving and learning.
Mike Rother RETIRE THE PDCA WEDGE? 2

3. IS THE PDCA WEDGE BASED ON A MISCONCEPTION?
There is a popular concept that
we can utilize standards to
maintain a process condition.
Such standards are often
depicted graphically as a
wedge that prevents the
process from backsliding.
However, it is generally not
possible simply to maintain a
level of process performance.
Process performance tends to
degrade no matter what, even if
a standard is defined, explained
to everyone, posted and
regularly audited.
This is not because of poor
discipline, but due to
interaction effects and entropy,
which say that any organized
process naturally tends to
decline to a chaotic state if we
leave it alone.
Where did the wedge concept come from?
Mike Rother RETIRE THE PDCA WEDGE? 3

4. ITʼS PROBABLY NOT FROM DEMING
In the “Act” part of the PDSA cycle, Deming talks about
“adopting the change.” That is, if a solution or
countermeasure has been successfully tested you
might decide to make it permanent.
Deming seems to be talking about standardizing not to
prevent slipping back, but simply in regard to putting a
tested countermeasure into place.
Deming makes a different statement on the topic of not
slipping back: you have to keep turning the PDCA
wheel. To maintain gains and uniformity, you have to
keep improving.
“Continue the cycle, over and over, with never-ending improvement of
quality, at lower and lower cost.”
~ W. Edwards Deming, Out of the Crisis, p181
“Quality of a product does not necessarily mean high quality. It means
continual improvement of the process, so that the consumer may
depend on the uniformity of a product and purchase it at a low cost.”
~ W. Edwards Deming, 1980
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5. ITʼS PROBABLY NOT FROM TOYOTA
The Toyota way of thinking about many standards is that
they are more like something you are striving to achieve.
The standard itself doesnʼt make anything happen. Itʼs a
definition of where you want to be.
Standard Standard
Actual Actual
A “standard” is a description “Standardized work” means, in
of how a process should essence, that a process is
operate. Itʼs the intended, actually operating as specified
normal pattern. by the standard.
Consider this: Toyota is achieving quality excellence not
because processes are done the same way each time, but
because Toyota is striving to achieve the target condition
of processes being done the same way each time.
Itʼs a subtle but important distinction.
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6. WEDGE WAY versus TOYOTA WAY
Wedge thinking Toyota thinking
When an abnormality occurs When an abnormality occurs
Weʼre slipping We arenʼt
back there yet
What is preventing
We need us from reaching the
to maintain target condition?
The operators Management is
are responsible responsible
We need more What is the
discipline! next step?
In the wedge way of looking The Toyota way of thinking
at it we think an abnormality turns this around: the
means weʼre slipping back, abnormality means we have
and itʼs someoneʼs fault. not yet have reached the
target condition. There are
still obstacles.
Illustration from Toyota Kata, page 115
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7. WHY DID WE COME UP WITH
THE WEDGE CONCEPT?
One reason may be that we think in terms of improvement
projects (start, stop, move on), which leads us to an audit &
compliance mindset.
This thinking may in turn be based on a desire for certainty
and misunderstanding of what is ʻscientific.ʼ
• Quantification and precision
What we
• Objective and certain
may think
scientific is • Reveals what is there
Eg: a standard is definitive
• Involves uncertainty,
ambiguity & incompleteness
What
scientific • Never free from error
really is • A process of discovery, via
systematic trial and error
Eg: a standard is a hypothesis
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8. WE NEED A STANDARD, OF COURSE
Thereʼs no genie who, without us defining the desired
standard, is going to make processes work in a way that
serves customers with highest quality and lowest cost.
But, likewise, just because weʼve defined a standard does
not cause a genie to appear and make things so and hold
entropy at bay.
So a process needs a standard.
But how does it work?
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9. A STANDARD IS LIKE A TARGET CONDITION
A standard is an idea of where you want to be
ent
rovem
Imp
Itʼs here!
The standard
is not here
Rather than a backstop, a standard is something you aspire to.
Just waiting for deviations and abnormalities and then
reacting to them is not enough. Without something to strive
for, entropy will set in no matter what you do.
Mike Rother RETIRE THE PDCA WEDGE? 9

10. BOTTOM LINE
Thereʼs no steady state
The point is that any process is either slipping back
or being improved, and the best and perhaps only
way to prevent slipping back is to keep trying to
move forward - every process every day - even if
only in small steps.
The best way to sustain results is to make
improvement toward your vision part of normal
daily activity.
Fortunately, striving toward a target condition is
highly motivating, brings a team together and can
be a lot of fun.
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11. SO LETʼS RETIRE THE WEDGE
Itʼs a lifelong process of striving, for which we are well equipped.
We can practice, learn and teach a fundamental way (a kata)
for meeting challenging target conditions along uncertain paths.
Mike Rother RETIRE THE PDCA WEDGE? 11