Page 215 - The Toyota Way Fieldbook

Chapter 8. Build a Culture That Stops to Fix Problems 191

Case Example: There’s Always More Than
One Way to Prevent Errors

In the Toyota Georgetown plant the parts were painted in a leveled color
mix and sequence, meaning that one part would be painted white, the
next might be blue, then black, and then back to white. It was possible
to have the same color back-to-back, but the mix varied according to
several conditions. The paint system required continuous circulation
of paint, and only one paint gun per painter was used. Each time the
color was changed, the painter would disconnect the paint line from
the QD (quick disconnect) and attach it to the paint gun. The painter
would flush the line momentarily and then paint the next part. Because
the color changed from part to part, the painter had to disconnect and
reconnect the paint line for each part. One key element of error proofing
lies in understanding that people will generally behave like electricity—
they’ll seek the path of least resistance. In this case the painters wanted
to avoid the continuous changing of paint lines.
Each paint booth had three painters. After the first painter applied color
to the part, subsequent painters could visually see the colors of the
parts (and the color mix) coming to them. On occasion the pattern
was such that a white part was followed by a red and then another
white, for example. When the painter could see that the white would
be needed again, he or she would hold the white line and reconnect
it after the red part (never reattaching the white line to the wall).
Sometimes the painter would deviate from the rule and have multiple
lines disconnected at one time, which caused the operator to mistakenly
reconnect one paint-line color to a QD of another paint color. Then
both colors would be mixed throughout the entire system—a big
problem! This happened several times each year, and the total lost
labor, materials, and waste disposal amounted to over $80,000 per year,
which did not include the cost to the customer (the assembly line).
The paint line would stop while the team leaders prepared hand-mixed
paint in “paint pots” for each painter so the line could be restarted.
The line stoppage often created a shortage of parts to the assembly
line—now a very serious problem. Previous efforts at error proofing
yielded the following “solutions”:
1. Notify the painters that the standardized work specified only one
paint hose be removed at any time and that standardized work must
be followed. As might be expected, this level of error proofing—
tell the employees the correct method—is rarely effective.
2. Post a sign that stated “Only one paint hose can be removed at any
time” at each workstation. This commonly applied attempt at error