the supermarket is maintained at the lowest possible level, and only remains
low until the value stream operations are capable of true flow.- Connected processes.Notice that the supermarket illustrates connecting
two processes together through pull. The lane with a triangle, circle, and
square also shows a connection. This indicates a “sequenced flow”—the
flow of material from operation to operation in the same sequence. This is
sometimes referred to as a FIFO (first in, first out) lane. These connections
are specifically defined in Chapter 5. - Flow loops.The supermarkets will delineate the beginning and end of a
flow loop. They also become the “customer” for each flow loop. The
objective is to always satisfy the customer. Although the “true” customer
is the operation withdrawing from the supermarket, the consumption from
the supermarket represents the demand. In the case of a custom or high
variety producer, there may not be a supermarket. The value stream in
that case might be one flow loop from beginning to end. - Simplified information flow. A key aspect of a lean value stream is the
simplification of information flow within the stream. Information is either
external or internal. External information from the customer enters the value
stream at one point only. All other information about what’s needed to com-
plete the work is generated internally. If supermarkets are used, the
supermarket is the source of information. If sequenced flow is used, the
information flows with the product. “Schedules” are dictated by one of
these processes. We see below, in Figure 3-2, that some mechanisms act as
the “voice of the customer.” This information flows to the process to dictate
what is to be done and when. - Awareness of the customer requirement. Awareness means an actual
physical awareness in the work area. It is not a schedule on a sheet of paper.
This will be explained further in Chapter 5, but briefly, it includes the use of
signals (kanban), and physically defined connections between operations. - Pacesetter.Every value stream must have a pacesetter (called the “pace-
maker” in Learning to See), and within the value stream, each flow loop
must have a pacesetter. The value stream pacesetter will ultimately dic-
tate the pace for all operations, but supermarkets act as a divider of flow
loops, and thus require a separate pacesetter.
Limitations of the Value Stream Mapping Approach
When Mike Rother and John Shook wrote Learning to See,they realized there was
a danger in getting this book out to the public. They were afraid it would appear
to be a cookbook, making lean as easy as following steps 1, 2, 3. Unfortunately,
the reality is far more complex. There is a reason that within Toyota you spend
Chapter 3. Starting the Journey of Waste Reduction 47