What is Six Sigma ?
An Explanation of Six Sigma
Goals and Processes
Developed and championed by Motorola engineers in the
1980's, Six Sigma is an attempt to increase traditional quality levels
from measuring defects per thousands to measuring defects per millions.
Six Sigma methodology addresses variability in design,
production, services, processes and measurement. Decreasing a process's
variability increases control and predictability of the process, resulting
in increased quality, reliability and performance, while reducing cost.
There are four main sources of process variation:
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Poor design resulting from bad design practices, unrealistic
or unclear requirements and requirement shift and creep
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Variation in a manufacturing process due to varying
manpower levels, work methods and ethics, environmental factors, training
and machine wear
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Variation in measurement systems due to improper calibration
and implementation
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Variation in parts and supplies from venders and subcontractors
The name Six Sigma refers to the six standard deviations
in process's normal distribution. Like groupings on target, Six Sigma's
goal is a process centered within a specification and having very little
variation, as shown in Figure 1.
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Scattered
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Centered with High Variation
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Off-Center with Low Variation
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Centered with Low Variation
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Figure 1. - Process Distributions
As a team project, Six Sigma has five phases:
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Design - In the Design Phase, the team identifies
the problem and project scope.
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Measurement - In the Measurement Phase, the team identifies
critical characteristics, maps the value stream and validates a measurement
system.
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Analysis - In the Analysis Phase, the team determines
the current process capability and causal relationships in the process
and identifies variability.
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Improvement - In the Improvement Phase, the team conducts
experiments , identifies variable relationships and takes corrective action.
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Control - In the Control Phase, the team monitors
performance, determines the new process's capability and analyzes the process
to identify and eliminate potential mistake activities.
This Six Sigma process is commonly referred to by
its acronym DMAIC.
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