Page 207 - The Toyota Way Fieldbook

Chapter 8. Build a Culture That Stops to Fix Problems 183

Operator Work Zone Operator Work Zone Operator Work Zone

Pull Cord

50% Response
Work Fixed time before
Position line stops
Visual
Stop
indicators of
work progress
Figure 8-4. Fixed position stop system

Line A

Line B Small defined
Small defined buffer
buffer Line C

Figure 8-5. Fixed position stop and small buffering

corners. Aline stop is really a line-segment stop. Each segment of the line can
stop briefly without stopping the others (Figure 8-5). As we noted, small inter-
mittent line stoppages are disruptive to the flow. Imagine traffic stopped at a
red light. When the light turns green, what happens? Do the cars all move simul-
taneously? No, they begin to move one by one until eventually all are moving.
This same phenomenon occurs when attempting to initiate flow. Small, defined
buffers at the corners are used to absorb minor interruptions—no more than 10
minutes total buffer. If an operator activates the andon and the leader responds
before the car has moved to the next work zone, the line never actually stops. If
the problem is more significant and cannot be corrected before the end of the
work zone, one segment of the line will stop (e.g., Line A), but the other lines (B
and C) will continue, provided there is product in the buffer. If the stop time
exceeds the capacity of the buffer, the following line will then stop due to shortage.
Of course, these buffers are very small so that larger problems are not hidden
by inventory.