182 THETOYOTAWAYFIELDBOOK
Minimizing Line Stop Time
Toyota has developed a system that allows problems to be identified and elevated
without necessarily stopping the line. When a problem is identified and the cord is
pulled, the alarm sounds and a yellow light are turned on. The line will continue to
move until the end of the work zone—the “fixed position stop” point (Figure 8-4).
The fixed position stop is especially useful for reducing actual line stops in the case
of a worker who is behind in the work sequence. Markings are placed on the floor
throughout the work zone that indicate the corresponding step of the standardized
work. If the leader responds quickly and can reset the line by pulling the cord again
before the fixed position stop is reached, the line will continue without interruption.
Failure to reach the line in time or if the leader determines the problem warrants it,
the line will stop when the fixed position is reached and the andon will turn red.
Many smaller problems can be corrected in this way without the annoyance
of repeated starts and stops of the line. Also note that anytime the line is
stopped, the problem is compounded because everyone on the line has to get
resynchronized with the line when it restarts. Toyota also uses an audible alarm
to signal all operators that the line is restarting.
Toyota assembly lines are generally very long and snake around corners. This
can be viewed as a series of straight line segments connected by “U” shaped
TIP
Develop Stability and Support Before Attempting to
Implement Stop the Line
As we will see Toyota lines do not immediately stop when the
andon cord is pulled. There is a very short time window (maybe 5
to 30 seconds) after the cord is pulled and before the line stops so
that the team leader can respond and override the line stop if war-
ranted. This system is very sensitive and requires a responsive
support structure with high capability. Clearly, Toyota did not
reach this level of capability overnight. Ahigh level of stability
was reached first so that the line does not stop continually and
investments were made in developing a team leader structure to
almost instantly respond to the andon calls. Move forward with
your own implementation of andon in such a way as to balance
the urgency to respond with the level of problems within your
processes. If your processes are not reasonably stable, you will
overload your support system and things will quickly unravel.