situations, and in many others several iterations through the continuous
improvement spiral would be required before attaining this level of capability.
As an analogy, imagine a bucket brigade line where the bucket is passed
from person to person one at a time. The ultimate single-piece flow would allow
the passing of a single piece from one member directly to the next. This would
require perfect synchronicity between all members of the brigade. After hand-
ing off one bucket to the following member, a turn is made to the previous
member to retrieve another bucket. Unless the timing between the two mem-
bers is absolutely the same, one of the members will wait on the other, which is
a form of waste. This level of precision would be exceptionally difficult, and
only possible in cases where the cycle time balance is perfect. Any slight falter
or misstep by one person on the line would throw off all the others, and the
house could burn down in the meantime.
In most manufacturing operations utilizing one-piece flow, a single piece is
placed between the workstations, allowing for minor variance in each worker’s
cycle time without causing waiting time. Even at this level, the cycle time balance
between operations needs to be exceptionally high. Additional pieces between
each operation allow for greater variation in cycle times from operation to oper-
ation; however, this also increases the waste of overproduction. This is the conun-
drum. Decrease the buffer between operations to reduce overproduction, and
increase the losses due to imbalanced work times.
There is a happy medium as you move forward with the creation of lean
processes. That medium point will provide a certain degree of urgency for prob-
lems, so they’re not ignored, and also a degree of cushion until the capability of
the operation is improved and a tighter level can be sustained. The continuous
improvement spiral model outlined in this section moves this cycle forward. The
90 THETOYOTAWAYFIELDBOOK
TIP
When Is a Problem Not a Problem?
Within Toyota, leaders are conditioned to not only stop and fix
problems, but also to continuously be on the lookout for prob-
lemsbeforethey occur. A well-established lean operation with
continuous, connected flow provides signals, which give everyone
an “early warning indicator” prior to complete system failure.
The ability to find problems before they occur allows leaders to
take preemptive corrective action, thus averting the failure.
Note: Within Toyota, “failure” is not considered to be a “bad”
thing. In fact, lack of failure is considered to be an indication that
the system has too much waste. Not knowing when and where the
failure will occur is an indication of a poorly designed system.