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Introduction to six sigma
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Session 1b - Six Sigma Overview
Pat Hammett - University of Michigan 1
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Six Sigma Overview
For more in-depth background, please read:What is Six Sigma?, Donald P. Lynch
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Topics
1. Six Sigma Overview2. Business Case for Six Sigma 3. Integration of Lean and Six Sigma4. Six Sigma Players5. Six Sigma Quality Level
Session 1b - Six Sigma Overview
Pat Hammett - University of Michigan 2
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1. What is Six Sigma?
Six Sigma is: a systematic methodology utilizing data analysis techniques, to measure and improve a company's business performance measures (Ys), by identifying and preventing 'defects and inefficiencies' in
manufacturing and service-related processes, to meet and exceed customer needs
Industry Implementations Successfully applied in numerous industries
automotive, discrete parts, aerospace, financial, health systems, etc. Within manufacturers, successfully applied to:
manufacturing Manufacturing Six Sigma operations/business processes Transactional Six Sigma
Nearly all systems involve an underlying process and benefit from reducing variation and/or improving flow
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Process-Driven Approach
Find and Fix (focus: existing problems) Apply DMAIC Problem Solving Method
Define, Measure, Analyze, Improve and Control
Prevention (focus: designing quality into new products) Apply Design for Six Sigma (DFSS)
e.g., IDDOV or DMADV Methods (not covered in this course)
Which do you suspect is more commonly applied? Which likely has a greater impact? WHY?
Process Outputs/ Metrics (Ys)Inputs (Xs)Key Product/Process
Output Variables (KPOV)Key Process
Input Variables (KPIV)
Session 1b - Six Sigma Overview
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Performance Measures, Ys
Gaps between customer expectations/ desires and what you provide. External Critical-to-Quality Measures (CTQ):
customer satisfaction, perceived value ratings, warranty Internal CTQ Measures:
scrap, rework, repeated tasks;
Processing inefficiencies and waste. Critical-to-Delivery (C-T-Delivery or CT-Time):
cycle time, lead time, overtime, service time, etc.
Of course, all of these are Cost Surrogates.
So, Six Sigma is about improving: Quality, Cost, Delivery (Q.C.D.) or Q.C.T. (T-time)
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The Six Sigma Way: Y=f(X) Sigma () - Greek letter used to represent standard
deviation which measures variation Six Sigma Approach: improve Ys by:
minimizing variation in inputs, or finding best settings for control factors, or managing noise factors
P-Diagram
ProcessInput Variables(e.g., supplier)
Controllable ProcessFactors (settings)
UncontrollableFactors
Outputs (Ys)
Xs
Session 1b - Six Sigma Overview
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Six Sigma Is it Anything New?
Grab any old Quality or TQM book and you will find: Most quality philosophies are the same as Six Sigma
e.g., customer defines quality, design quality in, etc. And many (but not all) tools / techniques are the same.
From an implementation standpoint, however, Six Sigma has been more successful through: greater emphasis on solving problems that result in savings
(bottom-line improvements, $$), common language and metrics (defect per million opportunity), common problem solving methods (Six Sigma DMAIC Method) integrating tools/methods into everyday job function, better training, more effective implementation.
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2. Business Case: Driver for Six Sigma Deployment
Core Belief: highest quality producer should be the lowest cost producer
Six Sigma aimed at reducing costs of poor quality
Many companies with large publicized savings* General Electric, Honeywell, Bank of America, ..
Note: Many companies have successful continuous improvement efforts that do not use Six Sigma (it is not the only way)
*Harry, M. and Schroeder, S. (2000). Six Sigma: The Breakthrough Management Strategy, Currency.*Smith, D, and Blakeslee, J. (2002). Strategic Six Sigma, Best Practices from the Executive Suite.*Six Sigma: A Methodology for Manufacturers, Not a Strategy. Gartner Report, September 2002.
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Costs of Poor Quality
Savings reported in large Six Sigma Deployment include traditional costs of poor quality and those below the surface (known as Hidden Factory)
Scrap Warranty Overtime Downtime
Rework
UnnecessaryInspection
EngineeringChanges
Rejected RawMaterial Costs
ResolvingCustomer
Complaints
Lost CustomerReplacement
Cost
ExcessInventory
ExtraCommunication
InformationLookup Costs
Clean-up/ Housekeeping
LongSetup Costs
ResourceImbalance
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Cost of Poor Quality (COPQ) Research
Link between quality defect levels and total costs of poor quality as % of sales*
*Harry and Schroeder (2000), Six Sigma Breakthrough Strategy, Currency
SIGMA LEVEL DEFECTS PER MILLION OPPORTUNITIES COST OF QUALITY
2 308,537 (Noncompetitive companies) Not applicable3 66,807 25 - 40% of sales4 6,210 (Industry average) 15 - 25% of sales5 230 5 - 15% of sales6 3.4 (World class) < 1% of sales
Each sigma shift provides a 10 percent net income improvement.
DPMO Defects per million opportunitySigma Level non-linear quality index related to yield (or % Ok)
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Why is Six Sigma working for some?
Strong Leadership Commitment Effective Deployment Strategies (Training, Organization,
and Management). And, because successful companies: take top employees, train them in the use of proven analytical tools, motivate them with greater recognition for their
efforts, give them projects to work on that matter, AND give them the necessary support to solve problems.
(such as time, software, resources).
Organization wants it to succeed!
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Why is it not working for others?
leadership offers marginal to limited support, egos get in the way (not-my-idea), managers dont give employees necessary
time/resources to complete projects, participants are pushed through training
programs, and do not develop the necessary skills to be effective,
Participants do not effectively communicate project savings / quantify impact.
Lack of organizational commitment!
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3. Lean and Six Sigma IntegrationCommon Theme: Continuous Improvement
Lean Tools/Methods
Organized and Documented Processes (e.g., 5S Workplace)
Create Flow Leveled Production Takt time planning Continuous flow Pull system Effective
Layout Quick changeover JIT supply chain 5 Whys
Visual Management and Standardized Work
Best Quality - Lowest Cost - Shortest Lead Time - Best Safety - High Moralethrough exceeding customer requirements and elimination of waste
Six Sigma Tools/Methods
Create Stable/Capable Process DMAIC Problem Solving and
Statistical Data Analysis Pareto Analysis (Prioritization) Cause-effect Analysis Measurement System Analysis Stratification Analysis Experimental Design Control Plans
Process Analysis Value Stream Map
Process Maps Eliminate Waste
Poka-Yoke
Right part, right amount,right time
Predictable, on-target, low variation, error-free processes.
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Different Paradigms for Lean and Six Sigma Integration
Six Sigma and Lean as Conflicting Six Sigma as a Sub-Set of Lean (Lean Bias) Lean as a Sub-Set of Six Sigma (Six Sigma Bias) Separate but Equals
- Most experienced with both strategies view Lean as an excellentprerequisite to Six Sigma, but not a standalone solution
- Six Sigma Complementary Strengths- Characterizing/decomposing process variation
(Strong link between smooth flow and low variation)- Techniques for Process optimization and robustness
Integrated/Complementary
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4. Six Sigma RolesManagerial/
Organizational
Problem Solving/ Execution
Executive Leadership: Set performance expectations
Champion:Deployment Leaders
Master Black Belts (MBB):In-House ExpertsTeach and Mentor BB, GB Figure out what to do
Black Belts (BB):Advanced Statistical SkillsSolve Impact Problems(e.g., $100-250K per project)
Green Belts (GB):Moderate Data Analysis Skills Work on simpler projects, orSubtasks of larger projectsMore GBs More Savings
They Do
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Applying the Six Sigma Tools
Green Belt and Black Belt Training focuses on: Structured approach to problem solving (DMAIC method) and data
analysis skills (statistical analysis tools)
Still, being an effective Green or Black Belt involves more than simply knowing statistics. It involves: Selecting right projects (with quantifiable savings) Project management skills (able to execute projects) Data collection skills (knowing what/how to collect) Data analysis skills (finding critical Xs) Data presentation skills (influencing decisions)
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5. Six Sigma Quality Level
Six Sigma Quality derives from a goal of % in-specification (or % On-Time) greater than 99.99966%, OR Less than 3.4 defects per million
opportunities (DPMO)
Note: 99% OK = 1% Defective = 10,000 defects per million (DPM).
Six Sigma seeks to do better!
*Based on assumption of stable process with low variation (Cp > 2) following normal distribution with a mean deviation within 1.5*process standard deviation of nominal
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Metrics used in Six Sigma
Use Historical Capability Measures: Yield, % defective, Cp/Cpk Example: % On-Time Delivery
DPM -- Defects per million (% Defective x 1M) where each unit is defective/not defective DPM = PPM (parts per million defective)
DPMO -- Defects per million opportunity where each unit may have 1 or more types of errors/defects
Paint Shop: dirt, craters, thin, sags, misapplied sealer Six Sigma Quality < 3.4 defects per million opportunity Note: if unit has only one defect opportunity, DPM = DPMO
Sigma Level index related to DPM/DPMO Non-linear Scale: ~ where a score of 6 equates to 3.4 DPM0)
Some common metrics used to evaluate performance:
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Conflicting Objective?
Suppose a Six Sigma project reduces defects from 40,000 to 1000 DPM (from 96% to 99.9%)
Should a Company: continuously apply six sigma resources (BBs / GBs)
toward reducing variation to less than 3.4 DPM, Or shift resources to another project with a greater cost (or
time) savings?
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Six Sigma Impact Problems
In the end, Six Sigma is about applying a data-driven systematic methodology to solve impact problems linked to: bottom line savings cost avoidance revenue growth