Six Sigma Methodology of Quality Assurance

Sidhartha Pattnaik,

(Certified Six Sigma Green Belt Professional)

Department of Mechanical Engineering

College of Engineering and Technology, Bhubaneswar

Introduction

In any industry, be it manufacturing or service, maintaining the quality of the product is highly essential. Quality control not only helps in ensuring cost effectiveness and higher productivity, it also helps to acquire higher profits and customer satisfaction.

“Six Sigma” Methodology is one such quality assurance technique. We can say Six Sigma is a methodology as well as a philosophy that improves the quality by analyzing data with statistics to find root cause of quality problems, improve the process and implement control. It is a technique of measurements which results in lower defects which converts into lower cost and competitive advantage.

Sigma (σ) is a mathematical symbol representing one standard deviation from average or mean. Six sigma refers to to +/- 3 σ from mean value. With six sigma there are only 3.4 defects in a million parts, technically called 3.4 DPMO (defects per million opportunities). A six sigma level process operates at 99.9997% quality level.

To think about in simple terms, let’s take an example, suppose we are manufacturing soda bottles in our company and our annual output is 1,000,000. If we are maintaining Six Sigma Quality level in our methods of production, there will be only 3.4 (approx. 4) defective bottles in the entire 10 lakh bottles. Isn’t it amazing?? Now let’s take the above examples and apply is to the traditional 3 σ quality level. In three sigma level there are 66,807 DPMO maintained at 93.3% quality level. Although 99.3% quality appears as a reasonable production output, but when we apply that to our soda bottle plant producing 1,00,000 bottles, there are 66,807 defects!!  To get hold of the seriousness quality in production and services, think about 1 million critical drugs in 3 sigma level, 66,807 defective drugs; 1 million child care medical services, 66,807 defective service! Quality is very critical to every aspect of service and production.

Now let’s take a close look at Six Sigma Methodology. How it started and where is it today.

Six Sigma and Organisation

Six Sigma effectively combines all previous quality management techniques like TQM( Total Quality management) and Lean Manufacturing. There are many pioneers whose contributions lead to development of the Six Sigma philosophy. But the credit for coining the term “Six Sigma” goes to Motorola Engineer Bill Smith along with Mikel Harry in 1980s. Six Sigma, till today is a registered trademark of Motorola.

Six Sigma can be viewed as a philosophy, a technique or a goal. Philosophy- Customer-focused breakthrough improvement in process; Technique- Comprehensive set of statistical tools and methodology; Goal- Reduce variation, minimize defects, shorten cycle time, improve yield, enhance customer satisfaction and boost bottom line.

Mathematically, six sigma represents six standard deviations from Mean.

USL- Upper Specification Limit, any deviation beyond this is a defect.

LSL- Lower specification limit, any deviation beyond this is a defect.

Target- this is the theoretical ideal value

The following table shows the yield and number of defects in various sigma level.

SIGMA LEVEL	DPMO	YIELD
One Sigma	690,000	30.9%
Two Sigma	308,000	62.9%
Three sigma	66,800	93.3%
Four Sigma	6,210	99.4%
Five Sigma	320	99.98%
Six Sigma	3.4	99.9997%

Six Sigma DMAIC Methodology

The six sigma methodology is conceptually based on a five phase project. Each phase has a specific purpose, tools and techniques which help in achieving the phase objectives and at the end, six sigma goals as a whole. The five phases of Six Sigma Methodology are Define Phase, Measure Phase, Analyze Phase, Improve Phase and Control Phase, in short DMAIC.

Define phase’s goal is to establish the project foundations, goals to achieve, current state of challenges etc. Which are articulated in a quantifiable manner. Valuation, Project Planning, Time Line etc are also part of this phase. The various tools used in this phase are Project Charter, Time line, Pareto Charts, SIPOC chart, Process Maps, CPM/PERT charts, Process capability indices etc.

Measure phase includes obtaining measurable baseline information about process, products etc. This also includes defining and identifying specific processes under investigation.  The tools used in this phase are Failure Mode and Effects Analysis(FMEA), Control Charts, Basic Statistics and Probability, Probability Distribution, Nominal Distribution, Graphical Analysis, Data Collection plan, ANOVA etc.

Analyse phase involved detailed statistical analysis of the project. Hypothesis Testing, regression analysis and other statistical tools are extensively used.

Improve phase is aimed only on making the improvement like improving the designing, testing and implementation of the solution from previous phases. Design of Experiment (DOE), Implementation Plan, Change Plan etc tools are used in this project.

Control phase establishes automated and managed mechanisms to maintain and sustain improvements in the process. Poka-Yoke, Statistical Process control etc are important tools here.

Six Sigma Professionals

Six Sigma methods are today widely used all around the globe across all industries. Hence highly skilled six sigma professionals are required. According to skills, experience and responsibilities Six sigma professionals are organised into Six Sigma white belt, Six Sigma Yellow Belt, Six Sigma Green Belt, Six Sigma Black Belt, Six Sigma Master black Belt and Six Sigma Champion.

Six Sigma White Belt (CSSWB), has basic entry level knowledge of Six Sigma from awareness perspective. He/She can participate in local problem solving teams that supports overall projects but not a part of Six Sigma Teams.

Six Sigma Yellow Belt (CSSYB), is an entry level Six Sigma professional who has general level knowledge of Six Sigma and its methods. Participates as a Six Sigma project team member and reviews project improvement techniques etc.

Six Sigma Green Belt (CSSGB), have in depth knowledge of Six Sigma Methods, processes etc; Leads six sigma Projects and Teams; Trains Yellow belt and White belt. Project management, Team Management and Task Management are all Green belt’s responsibility. A green belt also supports a Black Belt in collecting and analysing quality problems.

Six Sigma Black Belt (CSSBB) , leads Six Sigma project, trains and coaches project team. She/he understands six sigma methods and tools in details including supporting systems and tools. A black belt understands all aspects of DMAIC in exact details and has six sigma experiences over 3 years.

 Six Sigma Master Black Belt (MBB), trains and coaches black belts and green belts. A MBB functions more a Six sigma Program Level by developing key metrics and strategic directions. A MBB acts as an organisation’s six sigma technologist and internal consultant. A MBB has Six Sigma Experience over 10 years.

Six Sigma Champion is the highest level of six sigma professional organisation. A Six sigma champion translates company’s goals and vision to create an organisational deployment plan, identifies project, allocates resources and removes road blocks.

Six Sigma training and Certifications can be obtained from American society of Quality(ASQ), Aveta Business institute and many more organisations internationally. In India, Indian Statistical institute(ISI), KPMG, Benchmark Six sigma, Govt. Of India’s ICSL Vskills etc. provide six sigma certification and training. Various companies have their internal Six Sigma certification program tailored to their needs.

Other Quality Assurance techniques

Six Sigma is the highest level of quality assurance which incorporates previous techniques. But there are many quality techniques which are used along with six sigma. Kaizen, TQM, Just in Time Technique(JIT), Lean manufacturing etc.

Kaizen refers to any continuous improvement( large or small) in an organisation. JIT caters to need of customers when it occurs.

Lean manufacturing focuses on lean philosophy which is about waste elimination in all forms at workplace. 5S workplace organisation, Kanban, Muri and Muda are all Lean Techniques.

Conclusion

In today’s highly competitive economy, quality assurance is of utmost importance. Be is customer satisfaction, increasing profits, eliminating waste etc , Six Sigma plays a vital role in all these aspects. Companies today work to achieve six sigma level of quality competence at all levels.

Author

Sidhartha Pattnaik , is a final year B.Tech student of Mechanical Engineering at  College Of Engineering and Technology, (Biju Patnaik University of Technogy), Bhubaneswar. He is also a Certified Six Sigma Green Belt (CSSGB) Professional with ICSL Vskills Licence No. 7278. He can be reached at sidharthapattnaik28@gmail.com