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Lean SIX SIGMA in details


Md. Mustanzid Hasan Murad

Lean and Six Sigma are two widely acknowledged business process improvement strategies available to organizations today for achieving dramatic results in cost, quality and time by focusing on process performance. Lean Sigma combines the variability reduction tools and techniques from Six Sigma with the waste and non-value added elimination tools and techniques from Lean Manufacturing, to generate savings to the bottom-line of an organization. Six Sigma is such a management tool that is viewed as a systematic, scientific, statistical, and smarter approach to create quality innovation and total customer satisfaction. Six Sigma is a strategic initiative to boost profitability, increase market share and improve customer satisfaction through statistical tools that can lead to breakthrough quantum gains in quality. It also allows us to draw comparisons among all processes, and tells how good a process is. It provides efficient manpower cultivation and utilization. Six Sigma methodologies can be effectively applied to small, medium and large enterprises.

The garments industries which are traditionally operated are facing lots of problems such as low productivity, poor line balancing, high rejection, high defects, unable to achieve lead time. So defects minimization is the first condition of reducing cost and increasing productivity. Lean Six Sigma helps to eliminate these sorts of defects from textile and apparel manufacturing industry. It is a proven method for improving profits by pursuing perfection.

Possible areas in textile industry for Six Sigma application:

  • Reducing rejections in shipments
  • Improving first sample approval percentages while working with buyer
  • Improving supplier evaluation processes
  • Improving acceptable quality level (AQL) performance in shipments
  • Improving merchandiser performance
  • Improving processes at the source (including fabric purchase and inspection, stitching, embroidery, packing, and shipping) to reduce rejections at later stages
  • Eliminating manufacturing errors/defects

Lean Six Sigma

The whole structure of Lean Six Sigma is built on the foundation of the seven quality tools. The tools can be utilized in Kaizen projects, Quality Control Circles, Six Sigma Project and other important Lean Productivity functions.

  • Kaizen Projects
  • Quality Control Circles
  • Six Sigma Projects

Kaizen: Kaizen is about continuous improvement. All big Kaizen and big continuous improvement projects will have to reside on the study of the current state and that involves the analysis of data. Therefore these tools will help in the collection of data for the current state, analyzing the problems, and specifying the significant factors. After an analysis of the problem, corrective actions can be taken for improvements. The improvement will then be re-validated from these tools.

Quality Control Circles: The quality circles also work on work-floor challenges and projects. They conduct brainstorming sessions for problem analysis and solutions. Not only the fish-bone diagram can help but they can also find other tools useful for their circle activities.

Six Sigma Projects: Six Sigma Projects works on DMAIC (Define, Measure, Analyze, Improve and Control) and DMADV (Define-Measure- Analyze-Design- Verify). In every phase of the six sigma project, different tools are used. Those tools used in DMAIC and DMADV are somehow using basic seven quality tools.


What is Six Sigma?

Sigma is Greek for the letter ‘S’, and the term ‘sigma’ has been used for many years by statisticians, mathematicians and engineers, as a measurement unit of statistical variation. Six Sigma is a disciplined, data-driven approach and methodology for eliminating defects (driving toward six standard deviations between the mean and the nearest specification limit) in any process – from manufacturing to transactional and from product to service.

The UK Department for Trade and Industry says Six Sigma is: “A data-driven method for achieving near perfect quality. Six Sigma analysis can focus on any element of production or service, and has a strong emphasis on statistical analysis in design, manufacturing and customer-oriented activities.”

Lean Six Sigma is a fact-based, data-driven philosophy of improvement that values defect prevention over defect detection. It drives customer satisfaction and bottom-line results by reducing variation, waste, and cycle time, while promoting the use of work standardization and flow, thereby creating a competitive advantage. It applies anywhere variation and waste exist, and every employee should be involved.

Broad Approaches of Six Sigma:

Philosophy: The philosophical perspective views all work as processes that can be defined, measured, analyzed, improved, and controlled (DMAIC). Processes require inputs and produce outputs. If you control the inputs, you will control the outputs. This is generally expressed as the y = f(x) concept.

Set of tools: Six Sigma as a set of tools includes all the qualitative and quantitative techniques used by the Six Sigma expert to drive process improvement. A few such tools include SPC, control charts, failure mode and effects analysis, and process mapping. There is probably little agreement among Six Sigma professionals as to what constitutes the tool set.

Methodology: This view of Six Sigma recognizes the underlying and rigorous approach known as DMAIC. DMAIC defines the steps a Six Sigma practitioner is expected to follow, starting with identifying the problem and ending with the implementation of long-lasting solutions. While DMAIC is not the only Six Sigma methodology in use, it is certainly the most widely adopted and recognized.

Metrics: In simple terms, Six Sigma quality performance means 3.4 defects per million opportunities (accounting for a 1.5-sigma shift in the mean).

At this point, Six Sigma purists will be quick to say, “You’re not just talking about Six Sigma; you’re talking about lean, too.” Today, the demarcation between Six Sigma and lean has blurred. With greater frequency, we are hearing about terms such as sigma-lean, LSS, or Lean Six Sigma because process improvement requires aspects of both approaches to attain positive results. Six Sigma focuses on reducing process variation and enhancing process control, while lean—also known as lean manufacturing—drives out waste (non-value added activities) and promotes work standardization and value stream mapping. Six Sigma practitioners should be well versed in both.

History of Six Sigma:

Since the 1920’s the word ‘sigma’ has been used by mathematicians and engineers as a symbol for a unit of measurement in product quality variation. In the mid-1980’s engineers in Motorola Inc in the USA used ‘Six Sigma’ an informal name for an in-house initiative for reducing defects in production processes, because it represented a suitably high level of quality. In the late-1980’s following the success of the above initiative, Motorola extended the Six Sigma methods to its critical business processes, and significantly Six Sigma became a formalized in-house ‘branded’ name for a Performance Improvement Methodology. Bill Smith and Bob Galvin, both of Motorola, developed the Six Sigma quality improvement process in 1986. The idea of Six Sigma is to improve quality so that the number of defects becomes so few that they are statistically insignificant.

Looking at the success of Six Sigma at Motorola number of other companies, such as General electric, Dow Chemical, Dupont, Honeywell, Whirpool adopted Six Sigma. The credit of inventing Six Sigma goes to Motorola but General electric under Jack Welch has made it popular.

The Aim of Six Sigma Implementation?

The main goal of any Six Sigma implementation is quality improvement. The term originally comes from the sigma rating used to statistically rate manufacturing processes in engineering. A six sigma process occurs when no defects are expected in 99.99966% of all chances to produce them. This is the goal of any Six Sigma implementation. (3.4 defects per million)

It focuses on the use of statistical improvements to minimize defects in products and services. Precisely how that goal will be manifested will depend on what the product or service you are trying to improve. In some cases, the goal will be to transform the business. In others, specific problems need to be solved or perhaps the business is looking for strategic improvements. Whatever the goal, the process is essentially the same across implementations.


03The martial arts belt structure is used to recognize proficiency in training and application in Six Sigma, using the following colors:

White Belt – Overview, DMAIC, Define Phase

Yellow Belt – White Belt + process mapping, data collection and charting, assisting with a project

Green Belt – Yellow Belt + Project leader, core Six Sigma tools (Gage R&R, SPC, Capability, ANOVA) change management, hypothesis tests and more

Black Belt – Green Belt + advanced statistical analysis and experiments, change management, non-normal distributions

Master Black Belt – Black Belt + Design for Six Sigma, more advanced statistical analysis, unique tools for specific industries and processes, working with leadership, implementing successful improvement programs.

Six Sigma Process – DMAIC


Define (Organize)

The main objective of this phase is to summarize the project plan. This phase focuses on clearly specifying the problems; the goals of the process improvement project what is the scope of the project and identifying the customers (internal and external) along with their requirements. An input to this phase comes from the voice of customer (VOC), the voice of business (VOB) and/ or the voice of process (VOP). In addition, sometimes the voice of employees (VOE) is also effective to lead some six sigma improvement projects. With the help of these inputs, six sigma projects are identified. In this phase, we identify opportunity for six sigma projects. We develop a project plan and high-level process map. The main component of this phase is preparing Project Charter. Charter is a document, which is an initial blueprint for any six sigma project. It outlines following essential elements:

Business Case: It helps to understand how the project is linked to the overall business objectives.

Problem Statement: describes the problem or issue, this project is intended for.

Goal Statement: defines the project goal by considering all elements of SMART. The acronym stands for Specific, Measurable, Attainable, Relevant & Time-bound.

Project Scope: This considers in and out for this project. It defines the project boundary.

Team & their broad responsibilities: Project team description along with their responsibilities and roles during the project.

Time plan: Also, known as milestones. It ensures to keep a track on project progress as scheduled.

Estimated project benefits: Project benefits need to be estimated as a deliverable. Cost-benefit analysis is conducted & benefits, both tangible & intangible are speculated. This gives a direction to top management, whether to approve the project.

Charter is duly signed & approved by top management. Thus, gives a signal to go ahead for outlines project from Top executive. Tools in Define phase are required to measure CTQ (Critical to Quality) characteristics. The Pareto Chart and SIPOC (Suppliers, Inputs, Process, Outputs, Customers) are the valuable tools of this phase.

Measure (Process Data Collection)

The main objective of this phase is to collect the data that is relevant to the scope of the project. This phase focuses on identifying the parameters that need to be quantified, ways to measure them, collect necessary data and carry out measurement by different techniques.

The operational definition of metric is devised. It gives common language & understanding of data being collected. Data Collection plan outlines what data to be collected? When to be collected? Who will collect? Hence, sets overall direction for data collection. After data collection, data is analyzed to ascertain its nature through frequency distributions. The histogram can be used to understand the distribution of data. Depending upon data nature – Normal or Non – Normal, data – analysis tools are decided. Current Process capability is also an important aspect to be understood in this phase. In Measure phase, different tools can be used like Process flowcharts, Benchmarking, Run charts, Gage R & R and Process capability. Two commonly used measurement techniques are – Defects Per Million Opportunities (DPMO) and Process Sigma.

Analyze (Plan Process Layout)

The main objective of this phase is to find the root cause of business inefficiency. It identifies the gaps between actual and goal performance, determine its causes and opportunities for its improvement. Analyze phase follows a drill down approach to reach exact root causes from various potential causes identified initially. This phase starts with exploring all possible causes to the main problem. Then, these causes are verified & validated though hypothesis & statistical tools. The outcome of this phase is verified root causes – which need to be acted upon to improve the process. Analyze phase requires due care to identify & verify root causes. Because the effectiveness of process improvement through six sigma project lies on the correct identification of root causes. Commonly used tools in Analyze phase are Fishbone Diagram, Brainstorming, Histogram, 5 Whys, Hypothesis testing, Time series plots and Scatterplot.

Improve (Physical Change)

This phase improves the process by determining potential solutions, ways to implement them, test and implement them for improvement. In this phase, process owners are consulted and improvements are suggested. Action plan for the improvement is circulated to relevant stakeholders. This action plan specifies – Action to be taken; By when By whom etc. The improvement plan is designed to mitigate the risk and include customer feedback and satisfaction. With the formation of improvement action plan, implementation phase starts simultaneously. During implementation, actions are carried out, tested for effectiveness and implemented finally.

Tools used to eliminate the defects are Brainstorming, Mistake-proofing (Poka Yoke), Simulation software, Prototyping, Piloting and Pugh Matrix.

Control (Maintain Lean Six Sigma Operation)

The main objective of this phase is to generate a detailed solution monitoring plan. This plan ensures that the required performance is maintained. It defines and validates the monitoring system, develops standards and procedures, verifies benefits and profit growths, and communicates to business. Hence, the main purpose of Control phase is to ensure – Holding the gains.

During this phase, post-implementation results are evaluated. Progress is ascertained. And Changes are incorporated – if any, correction or modification is required. Control phase in most of the cases is a transition phase. Transition happens from current practices & systems into new practices.

The most important part of this phase is to provide training on new changes to all relevant stakeholders.