How Does Six
Six Sigma is a disciplined and
quantitative approach involving setting up a system and process for the
improvement of defined metrics in manufacturing, service, or financial
processes. The approach drives the overall process of selecting the right
projects based on an organization's business goals and selecting and training
the right people to obtain the results. Improvement projects follow a
disciplined process defined by a system of four macro phases: measure, analyze,
improve, control (MAIC).
Sometimes a preliminary step, define, is added
at the beginning, which relates to the appropriate selection of projects and
problem definition. The problem must be chronic and impactful.
The 4 MAIC phases will be described as
Measure Phase: Measure the existing systems. Establish valid and
reliable metrics to help monitor progress towards the project goals. Customer
expectations are defined to determine “out of specification” conditions.
- Identify and describe the potential critical
List and describe all of the potential critical processes obtained from
brainstorming sessions, historical data, yield reports, failure analysis
reports, analysis of line fallout and model the potential problems.
- Perform measurement system analysis
Determine precision, accuracy, repeatability
and reproducibility of each instrument or gauge used in order to ensure that
they are capable.
Analyze Phase: Analyze the system to identify
ways to eliminate the gap between the current performance of the system or
process and the desired goal. In this phase, project teams explore underlying
reasons for defects. They use statistical analysis to examine potential
variables affecting the outcome and seek to identify the most significant root
causes. Then, they develop a prioritized list of factors influencing the desired
- Isolate and verify the critical processes
Narrow the potential list of problems to the
vital few. Identify the input/output relationship which directly affects
specific problems. Verify potential causes of process variability and product
- Perform process and measurement system capability studies
Identify and define the limitations of the
processes. Ensure that the processes are capable of achieving their maximum
potential. Identify and remove all variation due to special causes. Determine
what the realistic specifications are. Determine confidence intervals. A
process is to be considered capable when it is in control, predictable, and
Improve Phase: In this phase, project teams seek the optimal solution
and develop and test a plan of action for implementing and confirming the
solution. The process is modified and the outcome is measured to determine
whether the revised method produces results within customer expectations.
- Conduct design of experiment
Select design of experiment factors and
levels. Plan design of experiment execution. Perform design of experiment to
find out the most significant factor.
- Implement variability reduction designs/assessments
Implement permanent corrective action for
preventing special cause variations. Demonstrate process stability and
Control Phase: Control the new system. Ongoing measures are
implemented to keep the problem from recurring. Institutionalize the improved
system by modifying policies, procedures, operating instructions, and other
- Specify process control method
Establish on-going controls for the
process based on prevention of special cause variation using statistical
process control techniques.
- Document the improvement processes