Management Guide: Six Sigma
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Contents Where
does the name Six Sigma come from Six Sigma DMAIC - Existing Product or Service
Improvement Six
Sigma DFSS - New Product & Service Introduction |
What is Six Sigma “Six Sigma” is a well-structured, data-driven methodology for eliminating defects, waste, or quality control problems of all kinds in manufacturing, service delivery, management, and other business activities. Six Sigma methodology is based on the combination of well-established statistical quality control techniques, simple and advanced data analysis methods, and the systematic training of all personnel at every level in the organisation involved in the activity or process targeted by Six Sigma. The statistical representation of Six Sigma describes quantitatively how a process is performing. To achieve Six Sigma, a process must not produce more than 3.4 defects per million opportunities. A Six Sigma defect is defined as anything outside of customer specifications. A Six Sigma opportunity is then the total quantity of chances for a defect. Process sigma can easily be calculated using a Six Sigma calculator. The fundamental objective of the Six Sigma methodology is the implementation of a measurement-based strategy that focuses on process improvement and variation reduction through the application of Six Sigma improvement projects. This is accomplished through the use of two Six Sigma sub-methodologies: DMAIC and DMADV. The Six Sigma DMAIC process (define, measure, analyse, improve, control) is an improvement system for existing processes falling below specification and looking for incremental improvement. The Six Sigma DMADV process (define, measure, analyse, design, verify) is an improvement system used to develop new processes or products at Six Sigma quality levels. It can also be employed if a current process requires more than just incremental improvement. Both Six Sigma processes are executed by Six Sigma Green Belts and Six Sigma Black Belts, and are overseen by Six Sigma Master Black Belts. According to the Six Sigma Academy, Black Belts save companies approximately $230,000 per project and can complete four to 6 projects per year. General Electric, one of the most successful companies implementing Six Sigma, has estimated benefits on the order of $10 billion during the first five years of implementation. GE first began Six Sigma in 1995 after Motorola and Allied Signal blazed the Six Sigma trail. Since them, thousands of companies around the world have discovered the far-reaching benefits of Six Sigma. Many frameworks exist for implementing the Six Sigma methodology. Six Sigma consultants all over the world have developed proprietary methodologies for implementing Six Sigma quality, based on the similar change management philosophies and applications of tools.
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Where does the name Six Sigma come from Six Sigma is a disciplined, data-driven approach and methodology for eliminating defects (driving towards six standard deviations between the mean and the nearest specification limit) in any process -- from manufacturing to transactional and from product to service The term Six Sigma defines an optimum measurement of quality: 3.4 defects per million events. The Greek letter SIGMA is a mathematical term that simply represents a measure of variation, the distribution or spread around the mean or average of any process or procedure in manufacturing, engineering, services or transactions. If we can reduce the standard deviation (average deviation in our product) then less of our product will be faulty. In other words lets make sure that everything we do is right first time by monitoring and removing mistakes. Why is so important to get things right? Say a product requires 40 operations to put it together. If one of these operations fails then the product is useless. If there is a 1 in 10000 chance of an operation failing then the probability of each operation being ok is 0.9999. The probability of the product being assembled correctly is. Probability of product being “OK” = 1 -(0.9999 * 0.9999 * 0.9999 and so on 40 times) = 0.399221%
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Six Sigma DMAIC - Existing Product or Service Improvement The DMAIC (Define, Measure, Analyse, Improve, Control) methodology should be used when a product or process is in existence at your company but is not meeting customer specification or is not performing adequately. The Six Sigma DMAIC methodology can be thought of as a roadmap for problem solving and product/process improvement. Most companies begin implementing Six Sigma using the DMAIC methodology, and later add the DFSS (Design for Six Sigma, also known as DMADV or IDOV) methodologies when the organisational culture and experience level permits. While the DMAIC methodology may appear linear and explicitly defined, it should be noted that an iterative approach may be necessary -- especially for Black Belts and Green Belts that are new to the tools and techniques that make up DMAIC. For instance, you may find that upon analysing your data (Analyse phase) you did not gather enough data to isolate the root cause of the problem. At this point, you may iterate back to the Measure phase. In addition, prior knowledge of the tools and techniques is necessary in determining which tools are useful in each phase. Remember, the appropriate application of tools becomes more critical for effectiveness than correctness, and you don't need to use all the tools all the time. DMAIC Phase Steps:
Click here for details of the DMAIC methodology.
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Six
Sigma DFSS - New Product & Service Introduction
DFSS is the acronym for Design For Six Sigma. Unlike the DMAIC
methodology, the phases or steps of DFSS are not universally recognised or
defined -- almost every company or training organization will define DFSS
differently. Many times a company will implement DFSS to suit their business,
industry and culture; other times they will implement the version of DFSS
used by the consulting company assisting in the deployment. Because of this,
DFSS is more of an approach than a defined methodology. DFSS is used to design or re-design a product or service from
the ground up. The expected process Sigma level for a DFSS product or service
is at least 4.5 (no more than approximately 1 defect per thousand
opportunities), but can be 6 Sigma or higher depending the product. Producing
such a low defect level from product or service launch means that customer
expectations and needs (CTQs) must be completely understood before a design
can be completed and implemented. One popular Design for Six Sigma methodology is called DMADV,
and retains the same number of letters, number of phases, and general feel as
the DMAIC acronym. It rolls off the tongue (duh-mad-vee) in the same fashion
as DMAIC (duh-may-ick). The five phases of DMADV are defined as: Define,
Measure, Analyse, Design and Verify.
A slight modification on the DMADV methodology is DMADOV
(Design, Measure, Analyse, Design, Optimise and Verify). There are a few other "flavours" of DFSS that you
might be interested to know about: DCCDI, IDOV and DMEDI. DCCDI is being popularised by Geoff Tennant and is defined as
Define, Customer Concept, Design and Implement. You can see that there are
many similarities between these phases and the DMADV phases.
IDOV is a well-known design methodology, especially in the manufacturing world. The IDOV acronym is defined as Identify, Design, Optimise and Validate.
Click here for details of the
IDOV methodology. DMEDI is being taught by PricewaterhouseCoopers and stands for
Define, Measure, Explore, Develop and Implement. As can be seen, the DFSS approach can utilise any of the many
possible methodologies. The fact is that all of these DFSS methodologies use
the same advanced design tools (Quality Function Deployment, Failure Modes
and Effects Analysis, benchmarking, Design of Experiments, simulation,
statistical optimisation, error proofing, Robust Design, etc.). Each
methodology primarily differs in the name of each phase and the number of
phases (and, of course, the acronym). How do you decide which DFSS methodology to use? If you're
hiring a consulting company to help with your deployment, use their
methodology, as their training materials will be tailored around it. If you
are implementing DFSS on your own, any of the DFSS books available should get
you moving in the right direction. In any case, following a detailed DFSS
methodology will help you achieve high quality levels for new products and
services. If you are interested in improving your existing products or
services, DMAIC is a more appropriate methodology to use. |
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DMAIC
Versus DFSS
Let's
first look at the DMAIC and DFSS methodologies and talk about how they're
alike. DMAIC and DFSS are both:
The DMAIC
methodology, instead of DFSS, should be used when a product or process is in
existence at your company but is not meeting customer specification or is not
performing adequately. DFSS,
instead of the DMAIC methodology, should be used when a product or process is
not in existence at your company and one needs to be developed, or the
existing product or process exists and has been optimised (using either DMAIC
or not) and still doesn't meet the level of customer specification or six
sigma level. |
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Quality Tools Associates are exposed to various tools and terms related to quality. Below are just a few of them. Control Chart – Monitors variance in a process over time and alerts the business to unexpected variance which may cause defects. Defect Measurement – Accounting for the number or frequency of defects that cause lapses in product or service quality. Pareto Diagram – Focuses on efforts or the problems that have the greatest potential for improvement by showing relative frequency and/or size in a descending bar graph. Based on the proven Pareto principle: 20% of the sources cause 80% of any problems. Process Mapping – Illustrated description of how things get done, which enables participants to visualize an entire process and identify areas of strength and weaknesses. It helps reduce cycle time and defects while recognizing the value of individual contributions. Root Cause Analysis – Study of original reason for nonconformance with a process. When the root cause is removed or corrected, the nonconformance will be eliminated. Statistical Process Control – The application of statistical methods to analyze data, study and monitor process capability and performance. Tree Diagram – Graphically shows any broad goal broken into different levels of detailed actions. It encourages team members to expand their thinking when creating solutions. |
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Quality Terms Black Belt – Leaders of team responsible for measuring, analyzing, improving and controlling key processes that influence customer satisfaction and/or productivity growth. Black Belts are full-time positions. Control – The state of stability, normal variation and predictability. Process of regulating and guiding operations and processes using quantitative data. CTQ: Critical to Quality (Critical "Y") – Element of a process or practice which has a direct impact on its perceived quality. Customer Needs, Expectations – Needs, as defined by customers, which meet their basic requirements and standards. Defects – Sources of customer irritation. Defects are costly to both customers and to manufacturers or service providers. Eliminating defects provides cost benefits. Green Belt – Similar to Black Belt but not a full-time position. Master Black Belt (or MBB) – First and foremost teachers. They also review and mentor Black Belts. Selection criteria for Master Black Belts are quantitative skills and the ability to teach and mentor. Master Black Belts are full-time positions. Variance – A change in a process or business practice that may alter its expected outcome. |
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Updated on August 21, 2002
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Copyright 2002 Allan Low. All rights reserved. Reproduction of this Web Site,
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