Between 1910 and 1920 variation was identified as a key source of product
defects. By the 1960’s, when Shigeo Shingo developed the concepts of
mistake-proofing known as poka-yoke, it is likely variation related defects had
been reduced through statistical process control to the point that mistakes were
already a significant fraction of production defects. Dr. Hinckley’s work in the
1990’s was the first to quantify the relationship between product complexities
and defect rates. This research also demonstrated for the first time that
variation, mistakes, and complexity were different sources of nonconformities
requiring distinctly different control methods.
Assured Quality has also shown that the most efficient
and effective way to eliminate defects is the reverse of the order of
discovery: first reduce complexity, then mistake-proof, and finally
implement control of variation with settings rather than adjustments. This
process is applied first to the product use, then to the assembly and
fabrication, and finally to the tools and equipment.
At every stage, we follow a simple six step process
derived from Toyota as shown here. Since improving quality is an
opportunity rich environment, in the first step, the highest priority
problems are identified and selected. After analyzing the problem,
multiple solutions are always generated. This step is the key to finding
less complex products and processes that provide more sophisticated
results. The alternative concepts are then compared and the best option is
selected. After implementation, the solution is evaluated. If effective,
the use of the concept is standardized throughout the organization.
To learn more about the most effective methods for controlling each of the
three key sources of defects, click on the links below.
