demistifying six sigma 22 09 2011

8/3/2019 Demistifying Six Sigma 22 09 2011

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Demystifying Six Sigma 22/09/2011

Six Sigma is about applying a structured, scientific method to improve any aspectof a business, organization, process or person. SS engages in disciplined datacollection and analysis to determine best ways to meet and guarantee customerneeds and satisfaction while minimizing wasted resources and maximising profit inthe process.

Six Sigma performance is the Statistical term for process that produces 3.4defects/errors per million of opportunities for defects.

SS treats the processes in a business/organization so that they deliver theirintended results reliably and consistently. Important characteristics are referred toas CTXs whereC CriticalT ToX Quality, Cost, Time, satisfaction etc whatever the characteristic is linked to eg

a Critical-to-Quality characteristic = CTQ

All of Six Sigma initiatives begin with one general purpose equation:

BREAKTHROUGH EQUATION

y = f (x) + e

Y:- Desired outcome/result

X:- Inputs that are required to create outcome

F:- Function, way or process through which input is transformed to outcome

E:- presence of error in terms of uncertainty in depending upon the inputsand transformation function to actually create desired outcome.

The characterization, analysis, measurement and control of VARIATIONS andultimately reduction or elimination of unwanted variation are a central theme toSigma Six improvements.

Six Sigma Personnel:1. Deployment Leader: Ensures alignment of corporate strategic goals with

business unit deployment plans.

Selects SS Champions2. Six Sigma Champion: Responsible for dissemination and successful

application of Six Sigma technical know-how. Selects Black, Green and yellow belts. Ensures they are

appropriately trained, tasked and deployed.

Reports progress against target metrics to deployment leaders andstakeholders. In smaller organisations above 2 roles may becombined and filled by one individual.

3. Core Team: Ensures completeness of deployment throughout theorganisation and is made up of cross-functional core leadership team.

4. Black Belt: This is Six Sigma highest level of skills. They are most highlytrained experts in Six Sigma complete set of tools and methods and aremasters at statistical problem solving. They are extensively trained,typically work full-time on Six Sigma projects, are accomplished withteaching skills and work with and mentor other practitioners. They possessknowledge and skills required to facilitate break-through level


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improvements in the most complex of processes. Typically number 1-2% ofthe organisation.

5. Green Belts: Trained and skilled to solve majority of process problems inorganisations. They are typically process owners, process leaders,professional staff, operational specialists, managers and executives withsignificant degrees of business leadership, statistical and problem-solvingskills. Typically number 5-10% of the organisation.

6. Yellow Belts: Six Sigma yellow belts are Everyone Else. Goal of Yellowbelts is to think in a data-driven, cause-effect process manner and applythis thinking to their areas of work.

DFSS :- Acronym for Design for Six Sigma is an approach for planning,configuring, qualifying and launching products/services/processes/system etcto move quality upstream in an organisation.

A six sigma culture starts with a clear understanding of who the customers are andwhat is required to complete customer satisfaction. How to build a workforce that

is totally committed to success of the company. Data systems must be establishedto measure and monitor customer satisfaction, improvement goals must be set andprograms initiated to achieve these goals. In a nutshell Six Sigma culture iscompletely focused on being result oriented, fuelled by continuous improvementand customer satisfaction.

Key Elements of Six Sigma are:

Focused on Customer Satisfaction

Data

Reach out-goals

Team based All employees involvement

Personal growth

Clear definition and understanding of roles

Every Six sigma process is a closed-loop system of interactions where customersatisfaction is clearly understood, measured and continuously improved.

Many Six Sigma programs include continuous improvement models like DMAICmodel acronym for

1. DEFINE: Affinity diagram may be used to generate a business-case as

business bottle necks and pain points are identified, recognized anddefined. This is the outcome of an exercise whereby members of the teamwrite their brainstorming ideas on to small individual pieces of paper (stickynotes) which are then arranged into natural logical categories/groupingsthrough an iterative process of refinement. Through this exercise, theoutput (Y) is defined i.e. what needs to be improved, its associatedprocesses and their location, cost and impact of the problem etc. Note thatProject scope is naturally too large when output definition is more thanone.

2. MEASURE: This is generally, the most difficult and time consuming phase inthe DMAIC methodology. Measurement and statistics are the ultimate sourceof problem-solving power. The effectiveness of Six Sigma is dependent upontaking accurate and appropriate performance measurements.


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Variation diminishes ability to consistently produce quality products, meetschedule and stay under budget.

Types of Variations:1. Common-Cause Variation: This is natural and can not be eliminated but can

be reduced. Also termed Short-Term variation which is measured by takingthe differences between any two sequential measurements of a criticalcharacteristic.R1 = |X1 X2

Entitlement is the level of variation that is naturally built into a process.This is acceptable level of variation you can expect from a process underthe best conditions:- Just another name for common-cause or short timevariation.

2. Special-Cause Variation: These are specific issues/causes that can be

identified and resolved.Six Sigma works on reducing Special-Cause variations first to prevent causecreep out of tolerable allowance level thereby making entire process morepredictable and stable. In Six Sigma terms Leverage is the ability to apply thefew critical inputs (Xs) that have the greatest impact on desired output (Y).

3. ANALYZE:4. IMPROVE:5. CONTROL:

In most instances an initial step RECOGNIZE comes before Define and the endprocedure is REALIZE.

Continuous improvement cycles are premised on fact that quality is improved byeliminating the causes of poor quality. Thus isolating root cause of poor qualitythrough use of stratification techniques and subsequently improving upon these willlead to improved quality.

Continuous improvement cycle sequence flow:

Data => Information => Actions => Results

SEVEN TOOLS OF CONTINUOUS IMPROVEMENT

1. Pareto Diagram: A graph of rank-order defect data used to prioritizecontinuous improvement projects and team activities.

2. Fishbone Diagram: A framework used to identify potential root causesleading to poor quality.

3. Check Sheet: Form designed to collect data.4. Histogram: A graph of variable data showing a pictorial view of distribution

of data around a desired target value.

5. Stratification: Method used to identify and narrow down causes of poorquality or defect to specific source i.e. individual, machine, department etc


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6. Scatter diagrams7. Charting: Graph used for tracking effectiveness of improvement programs.

Six Sigma Steps

1. Create operational statement and metrics This is a concise statement ofwhat needs to be/will be improved. At this stage, problem and objectivestatements are developed.

2. Measure performance and define the Improvement Teams: This enablesdetermination of the few vital factors that influence process behaviourthrough the use of statistics to describe performance in terms of numbersand measurements.Distribution: Is a Statistical term used to describe relative likelihood ofobserving values for a variable factor using three different measures ofdistribution location mean, median and mode.

Mode: This is the value most frequently observed and its associated withthe highest peak of a distribution.Mean: This is the most common measure of central tendency widely calledaverage.Median: This is the point along the scale measure where half thedata/value is below and half are above. This method is particular usedwhen collected data contains extreme data points well outside the range ofother data in other words outliers

From above, its simply not good enough to collect performancemeasurement data, there is the need to quantify how widely or narrowlydispersed the data are around their central location.

The easiest way to measure spread of data is range which is the differencebetween the largest and smallest observed data value.

Capability: Describes how well process (vital characteristics) performs inmatching Customer expectations.RUMBA:is used in Six Sigma to evaluate appropriateness of any specificationas explained below

Reasonable

Understandable

Measurable

Believable

Attainable

3.4.Six Sigma continuous improvement program requires prioritizing improvementactions and establishing improvement team to deal with predominate reasonsfor customer dissatisfaction. Alignment shifts from allocating team members toproblems to allocating problems to teams. Ideal tool for usage is PARETODiagram. This is a bar chart that displays reasons for defects and number ofdefects for each reason or category based on principle that 80% of defects canbe attributed to 20% of causes.5. Identify potential causes: Flowcharting is the best method to achieve this.

There are two basic flowcharting types, Linear and interdepartmental


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both of this will reveal the AS IS state of the enterprise. This enablesimprovement team to reengineer the system to Should Be state.

Linear Flowcharting is generally used where there is only a singledepartment involved in the producing the service or product.

Inter-Departmental flowcharting is used where two or more

departments are involved in producing the product or service.Alternative method of identifying and generating list of potential rootcauses is FISHBONE Diagram.Operational statement forms the head of the fish while

Materials

Manpower

Methods and

MachineMake up the four major bones

6. Investigation and Root cause Identification: This requires a major ACTIONPLAN with 4 main components;

WHAT is to be done

WHO is it assigned to

WHEN is completion schedule

Actual completion date

STATUS of actionitemsAs investigation into root causes progress CHECK SHEET is used to collectData while stratification, histograms and scatter diagrams are used toanalyze data.

Stratification looks for differences in the sources of variationobserved in the output of an operation.

Histograms are used exclusively to display variable data.Above 2 study causes of poor performance at individual operation or

process step level. Scatter Diagrams study specific effect one input variable will have on

output of a process step or operation.7. Make improvement permanent8. Demonstrate improvement

Six Sigma symbols/signs and meaning

1. => Standard Deviation2. => Mean3. => Sigma Score: This can be applied to the

performance of anything that has a specification and defect rate.

Six Sigma teaches that data and measurement are the starting point of continuousimprovement and development. Repeatability and Reproducibility (R&R) captureall measurement systems precision in other words how good the measurementsystem is. SS offers extremely powerful tools to aid improvement efforts, chiefamongst which is Experimentation. SS approach is to first design an experiment,carry it out and follow up with analysis to uncover previously hidden knowledge.


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Design of Experiments (DOE)

As opposed to Observational studies, control is set for the values Xs (input) takeon with objective to reveal, quantify and confirm underlying Y = f(XX) relationshipin a process or system. Key elements of efficient and consistently successful SSexperiments follow a progressive and iterative approach which include following:

Plan out experiment before conducting it

Explore the effect of more than one input variable at a time.

Minimize number of required runs in the experiment

Replicate key experiment conditions to assess variation

Account for known and unknown factors not directly included inexperiment.

Common type of experiment in SS:- 2k Factorial Experiment

Steps:1. Select the experiment factors by identifying the input variables Xs which

should be potential contributors to the output Y. Ideal number to choose isbetween 2 5 input variables.

2. Set the factor levels bearing in mind that all 2k factorial experiments use

only two levels for each input factor i.e. high and low values that boundsthe scope of the experiment.

3. Experimental codes and design matrix by deciding 2k number of unique runswhere k is the number of variables eg 2 raised to power 3 = 2 x 2 x2 = 8runs.

Control PhaseObjective of this phase is to establish measurement points for the critical Xs

(inputs) and other significant parameters of the process to assure that theCTQs (Critical-to-Quality) are predictable and meet establishes requirements.The most effective form of process control is sometimes refreerd to as A Type-1 Corrective Action :- This is control applied that eliminates error conditionfrom ever occurring. Second most effective is Type-2 corrective action :- Thisdetects when an error occurs and stops the process or shut down equipment sodefect is not propagated.Six Sigma emphasizes Control phase through implementing two aspects to acontrol plan:

Process Management Summary: objective is to enable visibility,review and action for all critical process outputs in an organisation.

Process Control plan: objective is to create systematic feedback

loops and actions to assure process inherent, automatic control. Statistical Process Control (SPC): Involves use of statistical

techniques to monitor and control variation in processes. PrimarySPC tool is Control Chart which is a graphical tracking of a processinput or output over time. These tracked measurements are visuallycompared to decision limits calculated from probabilities of theprocess actual performance. The different types of control chart aregrouped into 2 major categories:

- Continuous data control charts- Attribute data control charts

SIX SIGMA Practitioner Tools:These fall into two primary types:


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- Process optimization tools: Enables design, simulation andoptimization of processes

- Statistical analysis tools: Enables practitioners to analyzedata collected either from real-world performance of aproduct or process or as the output of a simulation orexperiment.

A. Process optimization tools1. SIPOC: Suppliers-Inputs-Process-Output-ControlsThis tool enables building the first controlled and organized view of work processand sets the foundation for applying the breakthrough DMAIC strategy. SIPOCsoftware tools like iGrafx, SigmaFlow and process modelling tools helps to capture,organize and display following:Steps

- Identify candidate process for mapping and define scopeand boundary points.

- Identify outputs- Define by name, title or organizational entity the recipients

of the outputs- Define the customer requirements- Define the inputs to the process- Identify the sources (suppliers) of the inputs

2. CT TreesThis is a tool that helps identify and characterize the influencers on specificoutcomes. Most CT trees begin with the output of the SIPOC, customer satisfactionat the top and other are subordinate. E.g Critical-to-quality, critical-to-delivery,Critical-to-cost etc.

3. Cause and Effect Matrix (C&E Matrix)Cause and effect helps the Six sigma practitioner to identify and prioritizerelationships between several inputs and the resulting outcomes. A variation of thisis the Fishbone Diagram.

4. Failure Mode Effects Analysis (FMEA)This is key to reducing or eliminating the risk of failures by providing a structuredapproach to identifying the potential ways a product or process can fail, howreadily can failure be detected and the effects of this. Furthermore, FMEA enablescontrolled planning, design and prioritization of actions to be taken to reducefailure risk. Analysis phase of FMEA is the process of determining probabilities andranking the results and one of the primary indicators is the Risk Priority Number.

(RPN) = severity rating X probability rating X detection rating

The outcome of FMEA leads to examination of fundamental designs, funnel reports,control plans and data collection plans. Iterative running of FMEA will reducefailure risk profile ti acceptable tolerance level.

5. Capability-Complexity Analysis (CCA)

6. Funnel Reports:This helps to filter through the trivial many, extract the critical few and manage

these. Sources of information for funnel report come primarily from the CT trees,C&E matrices and FMEAs.


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demistifying six sigma 22 09 2011

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