Six Sigma was originally developed as a set of practices designed to improve manufacturing processes and eliminate defects, but its application was subsequently extended to other types of business processes as well. In Six Sigma, a defect is defined as anything that could lead to customer dissatisfaction.
The particulars of the methodology were first formulated by Bill Smith at Motorola in 1986. Six Sigma was heavily inspired by six preceding decades of quality improvement methodologies such as Quality Control, TQM and Zero Defects, based on the work of pioneers such as Shewhart, Deming, Juran, Ishikawa, Taguchi and others.
Like its predecessors, Six Sigma asserts that –
• Continuous efforts to achieve stable and predictable process results (i.e. reduce process variation are of vital importance to business success.
• Manufacturing and business processes have characteristics that can be measured, analyzed, improved and controlled.
• Achieving sustained quality improvement requires commitment from the entire organization, particularly from top-level management.
Features that set Six Sigma apart from previous quality improvement initiatives include
• A clear focus on achieving measurable and quantifiable financial returns from any Six Sigma project.
• An increased emphasis on strong and passionate management leadership and support
• A special infrastructure of "Champions," "Master Black Belts," "Black Belts," etc. to lead and implement the Six Sigma approach
• A clear commitment to making decisions on the basis of verifiable data, rather than assumptions and guesswork.
The term "Six Sigma" is derived from a field of statistics known as process capability studies. Originally, it referred to the ability of manufacturing processes to produce a very high proportion of output within specification. Processes that operate with "six sigma quality" over the short term are assumed to produce long-term defect levels below 3.4 defects per million opportunities (DPMO). Six Sigma's implicit goal is to improve all processes to that level of quality or better.Six Sigma is a registered service mark and trademark of Motorola Inc. Motorola has reported over US$17 billion in savings from Six Sigma as of 2006. Other early adopters of Six Sigma who achieved well-publicized success include Honeywell , and General Electric, where the method was introduced by Jack Welsh. By the late 1990s, about two-thirds of the Fortune 500 organizations had begun Six Sigma initiatives with the aim of reducing costs and improving quality.
Six Sigma has two key methods: DMAIC and DMADV, both inspired by Deming’s Plan-Do-Check-Act Cycle. DMAIC is used to improve an existing business process; DMADV is used to create new product or process designs.
The basic method consists of the following five steps:
• Define process improvement goals that are consistent with customer demands and the enterprise strategy.
• Measure key aspects of the current process and collect relevant data.
• Analyze the data to verify cause-and-effect relationships. Determine what the relationships are, and attempt to ensure that all factors have been considered.
• Improve or optimize the process based upon data analysis using techniques like Design of experiments.
• Control to ensure that any deviations from target are corrected before they result in defects. Set up pilot runs to establishprocess capability move on to production, set up control mechanisms and continuously monitor the process.
The basic method consists of the following five steps:
• Define design goals that are consistent with customer demands and the enterprise strategy.
• Measure and identify CTQs (characteristics that are Critical To Quality), product capabilities, production process capability, and risks.
• Analyze to develop and design alternatives, create a high-level design and evaluate design capability to select the best design.
• Design details, optimize the design, and plan for design verification. This phase may require simulations.
• Verify the design, set up pilot runs, implement the production process and hand it over to the process owners.
DMADV is also known as DFSS, an abbreviation of "Design For Six Sigma".
One of the key innovations of Six Sigma is the professionalizing of quality management functions. Prior to Six Sigma, quality management in practice was largely relegated to the production floor and to statisticians in a separate quality department. Six Sigma borrows martial arts ranking terminology to define a hierarchy (and career path) that cuts across all business functions and a promotion path straight into the executive suite.
Six Sigma identifies several key roles for its successful implementation.
• Executive Leadership includes the CEO and other members of top management. They are responsible for setting up a vision for Six Sigma implementation. They also empower the other role holders with the freedom and resources to explore new ideas for breakthrough improvements.
• Champions are responsible for Six Sigma implementation across the organization in an integrated manner. The Executive Leadership draws them from upper management. Champions also act as mentors to Black Belts.
• Master Black Belts, identified by champions, act as in-house coaches on Six Sigma. They devote 100% of their time to Six Sigma. They assist champions and guide Black Belts and Green Belts. Apart from statistical tasks, their time is spent on ensuring consistent application of Six Sigma across various functions and departments.
• Black Belts operate under Master Black Belts to apply Six Sigma methodology to specific projects. They devote 100% of their time to Six Sigma. They primarily focus on Six Sigma project execution, whereas Champions and Master Black Belts focus on identifying projects/functions for Six Sigma.
• Green Belts are the employees who take up Six Sigma implementation along with their other job responsibilities. They operate under the guidance of Black Belts.
Quality management tools and methodologies used in Six Sigma
Six Sigma makes use of a great number of established quality management methods that are also used outside of Six Sigma. The following table shows an overview of the main methods used.
• 5W & 1H
• Analaysis of varience or Gap Analysis Study (GAS)
• ANOVA Gauge R&R
• Axiomatic design
• BPM – Business Process Mapping
• Catapult exercise on variability
• Cause & effects diagram (also known as fishbone or Ishikawa Diagram.
• Chi-square test of independence and fits
• Control Chart
• Cost-benefit analysis
• CTQ Tree
• Quantitative marketing research through use of Enterprise Feedback Management (EFM) systems
• Design of experiments. • FMEA – Failure Mode Effect Analysis.
• General linear model
• Pareto Chart
• Pick Chart
• Process Capability
• Regression Analysis
• Route Cause Analysis
• Run Chart
• SIPOC Analysis(Suppliers, Inputs, Process, Outputs, Customers)
• Taguchi Methods
• Thought Process Map
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