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What is it?
"Six Sigma" means a failure rate of 3.4 parts per million or 99.9997% perfect;
however, the term in practice is used to denote more than simply counting defects. Six
Sigma can now imply a whole culture of strategies, tools, and statistical methodologies to
improve the bottom line of companies. In all, six sigma is a rigorous analytical process
for anticipating and solving problems. The objective of six sigma is to improve profits
through defect reduction, yield improvement, improved consumer satisfaction and
best-in-class product / process performance. Why is it important?
World-class companies typically operate at about four sigma or 99% perfection. To get to
the six-sigma level means cutting down on huge costs and thereby the wasted dollars. For
example, if you are four sigma - you would be producing products at the rate of 6200
defectives for every million you produce vs. 3.4 defectives if you are at the six sigma
level.
When to use it?
Bottom line drives management action. What is your Cost of (poor) Quality? First you need
to determine that. Properly implemented, six sigma implementation can become a
profit-center for the company. Jack Welch at GE claims that the returns on six sigma
implementation amount to about $500 million as of 1998.
How to use it?
Six Sigma focuses on process quality. As such, it falls into the category of a process
capability (Cp) technique. Traditionally, a process is considered capable if the natural
spread, plus and minus three sigma (a yield of 99.73%), was less than the engineering
tolerance. A later refinement considered the process location as well as its spread (Cpk)
and tightened the minimum acceptable so that the process was at least four sigma from the
nearest engineering requirement. Six Sigma requires that processes operate such that the
nearest engineering requirement is at least plus or minus six sigma from the process mean.
This requires considerable scientific and testing actions - often thousands of tests are
run on multiple variables to get an understanding of what's going on. Once you determine
the process variables and using the other process analysis techniques, you need to
consider the ones causing the major losses and work on making them more capable.
- Understand who your consumers are
and what your product / service is
- Review consumer surveys, concession
reports, and other data
- Screen and prioritize issues by
severity, frequency/likelihood of occurrence, etc.
- Determine the internal processes
causing the most pain
- Find out why and where the defects
are occurring
- Devise ways to address these defects
effectively
- Setup a good metrics (six-sigma
places a lot of emphasis on measurement)
Who or what
is a Black Belt?
A leadership structure for process improvement teams is provided by the use of "Black
Belts" just as Total Quality utilized "Quality Improvement Team Leaders" to
provide structure. Black Belts are highly-regarded, technically-oriented product or line
personnel who have an ability to lead teams as well as to advise management.
Available on the web:
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