We use Shigeo Shingo’s mistake-proofing methods based on poka-yoke
(see examples).
This is the only technique which has proven to be effective in sustaining
defect rates below 50 parts per million at competitive cost. A comparison of
quality performance based on an international benchmarking study by a major
US corporation illustrates the effectiveness of Shingo’s methods. In this
study, the cost of the quality control efforts included the cost of scrap,
rework, repair, warranty and quality control. The U.S. Companies included in
the study were recognized as quality leaders, including several companies
aggressively pursuing 6 Sigma deployment.
Novices, who have not seen hundreds of examples, have a difficult time
developing good mistake-proofing concepts. This is one of the greatest
barriers in implementing mistake-proofing. Although many examples of
mistake-proofing are available, they have not been organized in a manner
that helps novices quickly find relevant solutions.
Assured Quality’s is the only mistake-proofing organization that has
addressed these issues and provides:
A mistake taxonomy that facilitates the organization of examples,
A catalog of more than 200 examples classified according to this
taxonomy,
A summary of the principles useful for controlling each specific
class of mistakes
A method for comparing and selecting the most effective
mistake-proofing concepts
Collectively, these tools help novices and experts quickly find relevant
examples, identify potential mistake-proofing principles, rapidly develop
superior mistake-proofing concepts, and pick concepts that work.
Assured Quality’s
Mistake Taxonomy
Defective Materials
Information Errors
Ambiguous Information
Incorrect Information
Miss-read, Miss-measure,
Miss-interpret
Omitted Information
Inadequate Warning
Miss-alignments, Adjustments, Timing
Misaligned Parts
Miss-adjustments
Miss-timed or Rushed
Omission or Commission Errors
Added Materials or Parts
Commit Prohibited Action
Omitted Operations
Omitted Parts & Counting Errors
Selection Errors
Wrong Concepts or Material
Select Wrong Destination
Select Wrong Location
Select Wrong Operation
Select Wrong Part
Select Wrong Orientation
Assured Quality’s Mistake-Proofing
Principles
For each type of mistake, Assured Quality has
summarized the principles that have been used to control that mistake. For
example, for just one of the classes of mistakes listed above, Inadequate
Warning, the following mistake-proofing principles have been identified,
among others:
Create warning signals as needed
Supplement existing warnings with signals in remote or isolated
locations
Use sensors to detect warning conditions
Make it easy to observe conditions that warrant warnings
Select the right warning method for the environment and conditions
(tactile, visual, or aural)
