In his book The Goal, Eliyahu Goldratt
effectively used a story written in a novel format to walk the reader through
the steps necessary to move a manufacturing organization from the traditional
manufacturing concepts to a facility managed using the concepts of Drum
Buffer-Rope (DBR). This nontraditional approach through logical thinking is
masterminded by a character named Jonah. Jonah is able to help Alex Rogo
understand the invalid thinking and assumptions being used to manage his plant
and the negative consequences associated with that type of thinking. By helping
Alex focus his thinking on how the plant is being managed, Jonah helps Alex
logically discover a new and better way. And Drum-Buffer-Rope (DBR) is the
centerpiece of this process. In this
posting I will “borrow” heavily from Appendix 6 from Epiphanized as written by Bruce Nelson.
The intent of this posting is not how to
implement DBR, but more the understanding of why system’s thinking is so
important in any improvement effort and why it is so important to view your
organization as a system rather than isolated parts when selecting the focus of
your improvement efforts.
The thinking behind DBR is really quite
simple, but mostly just logical. Thinking logically is nothing new, but it is
not the way most people think. The fundamental view of DBR is to focus on the system as a whole rather than only a
single segment of the system—at least until you have clearly identified the
constraint. This idea of looking at the global system is a major shift
in the way systems have previously been viewed and managed. Prior to global-systems
thinking, the pervasive point of view was (and still is) that any systems
improvement, at any location, would improve the overall system. The idea being
that the sum total of several isolated improvements would somehow equal an
improvement to the overall system. But such is not the case. The effects of
employing the “shotgun” approach to systems management can cause a series of
devastating systemic effects.
A system can be defined as a sequence
of steps or processes that are linked together to produce something as
an end result. With that definition in mind, it’s easy to understand how
virtually everything can be linked to some kind of a
system. Engineering organizations have systems, banks have systems and grocery
stores have systems. Almost anything you can think of is the product of a
system. By design, a system can be as small and unique as two processes linked
together, where the output of one process becomes the input for the next
process. Or systems can be very complex, with many processes linked together,
maybe even hundreds or more. Just because a system is complex does not mean it
can’t be improved—it just means it’s complex, and that’s OK. Even in a system
as simple as two linked processes, one of those two processes will constrain
the other. It’s just the nature of how things work. If a systems constraint did
not exist, then the system should, at least theoretically, be able to produce
at infinite capacity. But infinite capacity is not a level that is ever
achieved from a system. All systems are restricted, at some point in
time, by some type of output limitation. This limitation is usually determined
by the presence of some kind of system-capacity limit. No matter how good the
system is, there is still only so much it can do. Sooner or later whatever kind
of system is being analyzed, it is will reach its maximum system capacity and
be unable to produce more. If higher system outputs are required beyond the
current capacity, then the system must be changed.
For years, if not decades, people
and organizations have dedicated considerable time and effort to remove
variation from systems. The utopian goal is to remove as much variation as
possible from the system. No matter how much planning is employed, no matter
how much effort is extended, variation will still exist! If you were asked how
long it takes you to get to work every day, your response might be something
like, “about thirty minutes.” The instant you answer with the word about,
you have introduced variation into the system. You know that historically
speaking, some days you get to work in twenty-five minutes and yet others days
it can take thirty-five or forty minutes. In your “get to work” system, things
can happen that will either speed up the process or slow it down.
Variation exists in everything, especially
within a system. You understand that some processes will produce at a faster or
slower rate than others, and this is the premise behind variation. Because of variation, the output from a system will not be linear, but
rather it will operate within a range that changes. This variable range is
known as statistical fluctuation and it exists in every system. It’s
important to understand that you cannot make variation go away. The theory and
practice of Six Sigma has pioneered the race to variation reduction. But even
with the most valiant efforts of time and money, not all variation can be
removed. You can reduce the amount and severity of variation, but it will still
exist. Once you understand that variation is a constant variable in any system,
it’s easier to understand that at some point you will reach the minimum
variation that is controllable in the system and any efforts to reduce variation
beyond that point are fruitless. Perhaps, instead of spending so much time and
effort on techniques to remove variation, the focus should really be on techniques
to manage variation.
When viewing a system through the
eyes of DBR, it becomes quickly apparent that improving every step in the
process is not required, nor will the sum total of all of those discrete
system improvements equal an improved overall system. When conducting a full
systems analysis, with the intent of implementing DBR, an important
consideration to know and understand is the location of the system
constraint, or slowest operation. In Goldratt’s Five Focusing Steps, this
is Step 1—Find the constraint. Once you know where the slowest operation
resides, you now have the information necessary to know where to focus your
attention within the system. Why is it important to understand where the
slowest operation is? Because this is the location that controls and
determines the output for your entire system. In essence, the entire system
will produce no faster than the slowest operation can produce. (The system can
produce less, but it won’t produce more.).
With the constraining operation
identified, you have collectively quarantined the “drum” beat for your system.
Knowing the drumbeat is of strategic importance to implement and gain any system improvements. The drum provides
you with the necessary information of knowing where to focus your improvement
efforts.
Historically, many organizations
can and do conduct many improvement projects on a yearly basis. The mantra
seems to be that every organization and every process should strive for
improvement. The thought is that each organization is improving at some level
of frequency to make the whole system better. However, the sum of many efforts
does not always equal what is good for the whole. The problem with this type of
thinking is it is a totally unfocused shotgun approach to solve the
problem. In effect, it presents an improvement policy that states: if I select
a wide enough range, then I should hit the target, or at least come close to
the target. When you take the shotgun approach you might hit everything a
little bit, but miss the full impact required to make real change and
improvements. If your shotgun approach includes trying to improve non-constraints,
and most do, then the system as a whole gains nothing! The improvement of non-constraints
in isolation of the entire system, without a comprehensive analysis, is just a
way of dealing with symptoms and not the real issue (constraint).
Without the ability and the
accurate information necessary to focus on the real issues, the disease goes
merrily on. Improvement of non-constraints is a noble gesture, but one that
yields little, if any, real improvements. Every process within a system does
not need to be improved at the same time! Some system processes are more important
than others. Without knowing where your constraint resides, your efforts to
improve will be unfocused and consequently worthless, serving only to consume
large amounts of money, resources, and time.
So there you have it…..the
concept of system’s improvement versus uncontrolled localized improvement. We can’t emphasize enough just how important
it is to view the entire system when trying to decide where improvements should
be focused. I want to thank Bruce for
his valuable insights.
Bob Sproull
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