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Jidoka and Poka-yoke form one of the two pillars in the
house of Lean. (The other pillar is JIT, or Just-In-Time manufacturing.) Jidoka
is defined as "providing the ability to detect abnormal conditions and
immediately stop work". Poka-yoke is defined as "error-proofing or mistake-proofing
a process".
Generally, mistake-proofing has three levels: preventing
errors, reducing the impact of an error, and identifying errors. The following
sections provide some real-world examples of each.
Preventing Errors
- Specially-shaped
parts that can be installed in only one direction are designed to prevent
installation errors.
- In the
software world, many applications are programmed to prevent certain values
from being entered into a form.
Reducing the Impact
of an Error
- An
airbag does not prevent an automobile accident from happening, but it can reduce
greatly the human cost and anguish from a car accident.
- The SawStop®, a saw that
can detect a human finger and immediately stop the saw, can save the
operator from serious injury.
Identifying Errors
- Smart Bolts from Stress Indicator, Inc. are bolts that change color based on how
much they are tightened. The help users
avoid under tightening and over torquing conditions.
Learn from Deming
One of Edward Deming's 14 points is this: "Cease dependence on
inspection to achieve quality. Eliminate the need for inspection on a mass
basis by creating quality into the product in the first place."
Manufacturers mostly rely upon inspection (which usually occurs
after a product is made) to determine the quality of the product. Often, the
results of the inspection are not fed back to the process that created the
error, or the cause of the error is not readily known. By building systems and
cultures that immediately stop the process when an error is detected, the
process can be improved to reduce or eliminate those errors from occurring in
the future. This will eliminate waste and provide for satisfied customers in the
long run.
How are errors and problems handled at your
organization? Are your people rewarded
for bringing attention to problems? Can
you share any examples oferror-proofing where you work?
Additional Resources
Here are some links to additional resources for Jidoka and
Poka-yoke.
A brief tutorial on mistake-proofing written by John R.
Grout and Brian T. Downs
http://www.mistakeproofing.com/tutorial.html
Wikipedia Article
http://en.wikipedia.org/wiki/Autonomation
Society of Manufacturing Engineers – Lean e-newsletter
http://www.sme.org/cgi-bin/get-newsletter.pl?LEAN&20021209&1&
Previous Posts about Lean in CR4's Engineering Management
Blog
http://cr4.globalspec.com/blogentry/7657/A3-Reports-Methodology-and-Process
http://cr4.globalspec.com/blogentry/7101/Lean-Manufacturing-Part-1
http://cr4.globalspec.com/blogentry/7106/Lean-Manufacturing-Part-2
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