Transcript Slide 1

5 WHY
A method for rapidly determining the root cause of a problem
Example
Summary
The “Five Why’s” is a method for rapidly
determining the root cause of a problem
popularized by Taichi Ohno, the father of the
Toyota Production System. His technique was to
approach any problem and keep asking “Why”
until he was satisfied that the answer showed him
what was really the source of the problem. In
doing so, he then had a good idea of what needed
to be fixed to prevent the problem. He called it the
“Five Why’s” because he found over time that by
asking “why” five times he usually ended up with
the right information to go and fix the problem.
The Five Why’s should be used by individuals and
teams when trying to quickly assess and
determine source of problems. Most problems can
be handled this way, however more complex or
life/mission critical problems typically require a
more formal root-cause methodology including
documenting the analysis. However, even the
formal methodology requires asking “why” over
and over again.
1
Problem: High reject rate of parts used by
downstream aircraft assembly process
1) Why?
- There is bare material exposed
2) Why?
- The primer paint coating does not cover the
whole part
3) Why?
- The priming process does not ensure full
coverage
4) Why?
- The priming process is never done the
same way twice
5) Why?
- The priming process has always relied on
word-of-mouth training and has no
standard process defined
To improve, get the primers together to create a
standard work method that defines the exact
sequence and tools for priming the parts. This will
significantly improve the process yield. They can then
explore further improvements using their standard
work as the baseline.