This concept was created by Motorola in 1980s. The name refers to a scientific way of describing quality based on variations that occur in any process-plus or minus three ―sigmas.‖
Sigma is the Greek letter that signifies the standard deviations in a mathematical formula.-the ―sigma level‖ quantifies defects per million opportunities (DPMO) The term six sigma refers to a measure of process variation (six standard deviations) that translates into an error or defect rate of 3.4 parts per million. To achieve quality performance of six sigma level, special sets of quality improvement methodologies and statistical tools developed.
These improvement methods and statistical tools are taught to a small group of workmen known as six sigma champions who are assigned full-time responsibility to define measure, analyse, improve and control process quality. They also facilitate the improvement process by removing the organizational roadblocks encountered. Six sigma methodologies improve any existing business process by constantly reviewing and re-tuning the process.
To achieve this, six sigma uses a methodology known as DMAIC (Define opportunities, Measure performance, Analyse opportunity, Improve performance, Control performance).
Six Sigma Maintenance Process
- Define
This step involves determining benchmarks, determining availability and reliability requirements, getting customer commitments and mapping the flow process. - Measure
This step involves development of failure measurement techniques and tools, data collection process, compilation and display of data. - Analysis
This step involves checking and verifying the data and drawing conclusions from data. It also involves determining improvement opportunities, finding root causes and map causes. - Improve
This step involves creating model equipment and maintenance process, total maintenance plan and schedule and implementing those plans and schedule. - Control
This step involves monitoring the improved programme. Monitor improves performance and assesses effectiveness and will make necessary adjustments for the deviation if exists.
Quality assurance (QA)
It is a way of preventing mistakes or defects in manufactured products and avoiding problems when delivering solutions or services to customers; which ISO 9000 defines as “part of quality management focused on providing confidence that quality requirements will
be fulfilled‖. This defect prevention in quality assurance differs subtly from defect detection and rejection in quality control, and has been referred to as a shift left as it focuses on quality earlier in the process.
