flow is attempted prior to achieving stability, the impediments may be too large
and the creation of smooth, consistent flow will be impossible. A stable process
will also have a higher degree of flexibility and capability of meeting varied cus-
tomer requirements.
Chapter 4. Create Initial Process Stability 59TRAP
The Fallacy of Perfect Stability
We were involved as consultants in the early day of the implemen-
tation of the Ford Production System, modeled after the Toyota
Production System. There was general agreement on the impor-
tance of process stability before moving to the higher levels of lean.
There was also a strong belief that all plants around the world (over
130) had to move forward in roughly the same time frame. So the
first year was spent on process stability issues in one model area
that each plant selected, including 5S (see page 64), preventive
maintenance, and standardized work. The first year extended
into year two. It became clear that these seemingly simple tools
required a great deal of discipline and understanding and the
plants had little incentive other than “corporate wants us to do it
and is going to check up on it.” In later years this moved at Ford to
a more integrated approach where flow, pull, and stability were
better integrated in model areas. Process stability should have a
reason—to support value-added flow. Reducing waste and creat-
ing flow will make stability a necessity instead of a necessary evil
to please the corporate lean group.On the other hand, it’s possible to spend years trying to achieve perfect sta-
bility without moving to higher levels of flow and pull. Experience suggests
that this will lead to cycles of stability: dropping back to instability, reattaining
stability, and on and on. The reason is that there is no motivation to sustain the
higher levels of capability because the system is not tightened to require the
improved level. In a large batch operation without flow, a high level of stability
is actually not needed and thus the only motivation to continue using disciplined
process is to keep “lean managers” off your back.
Strategies to Create Stability
Table 4-1 shows the strategies utilized during the stability phase, as well as the
primary and secondary lean tools often utilized. Any particular tool may or may
not be used, depending on the circumstances of the operation. The objectives
and strategies, however, alwaysapply.