Six Sigma is a
business management strategy originally developed by Motorola, USA in 1986.
It improves the quality of process outputs by identifying and removing the
causes of defects (errors) and minimizing variability in processes. It uses
a set of quality management methods, including statistical methods. Each Six
Sigma project is carried out within an organization follows a defined
sequence of steps and has quantified financial targets. The maturity
of a process can be described by a sigma rating indicating its yield, or the
percentage of defect-free products it creates. A six sigma process is
one in which 99.99966% of the products manufactured are statistically
expected to be free of defects (3.4 defects per million).
Define the
problem, the voice of the customer, and the project goals. Some of the
deliverable at this stage are:
Measure key
aspects of the current process and collect relevant data. Some of the
deliverable at this stage are:
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Process Maps
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Data Sampling - Population vs. Sample, Classification
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Charts to assess Measurement System Stability
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Measurement System Analysis
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Statistical Process Control Charts
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Root Cause Analysis
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5-WHY
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Fishbone Diagram (Ishakawa Diagram / Cause and Effect Diagram)
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Correlation Matrix
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FMEA - Failure Mode Effects and Analysis
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Overall Equipment Effectiveness
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Spaghetti Diagram
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Baseline Measurement
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Defects per Unit
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Defects per Opportunity
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Defects per Million Opportunities
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Process Yield Metrics
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Final Yield
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Throughput Yield
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Rolled Throughput Yield
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Normalized Yield
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The meaning and formula around sigma scores
Analyze the
data to investigate and verify cause-and-effect relationships. Determine the
relationships, and attempt to ensure that all factors have been considered.
Seek out root cause of the defect under investigation.
Improve or
optimize the current process based data analysis, and standard work to
create a new, future state process. Set up pilot runs to establish process
capability.
Control the
future state process to ensure that any deviations from target are corrected
before they result in defects and implement control systems
