Chapter 10 Principles of Six Sigma MANAGING FOR QUALITY AND PERFORMANCE EXCELLENCE, 7e, © 2008...

Chapter 10Chapter 10

Principles of Six Sigma

MANAGING FOR QUALITY AND PERFORMANCE EXCELLENCE, 7e, © 2008

Thomson Higher Education Publishing1

Key Idea


Thomson Higher Education Publishing

Although we view quality improvement tools and techniques from the perspective of Six Sigma, it is important to understand that they are simply a collection of methods that have been used successfully in all types of quality management and improvement initiatives, from generic TQM efforts, to ISO 9000, and in Baldrige processes.

Six-Sigma Metrics

• Defect – any mistake or error that is passed on to a customer

• Defects per unit (DPU) = number of defects discovered number of units produced

• Defects per million opportunities (dpmo) = DPU 1,000,000 opportunities for error





Six-Sigma Quality Ensuring that process variation is half the

design tolerance (Cp = 2.0) while allowing the mean to shift as much as 1.5 standard deviations, resulting in at most 3.4 dpmo.

Key Idea



Although originally developed for manufacturing in the context of tolerance-based specifications, the Six Sigma concept has been operationalized to apply to any process and has come to signify a generic quality level of at most 3.4 defects per million opportunities.

k-Sigma Quality Levels



Problem Solving

• Problem: any deviation between what “should be” and what “is” that is important enough to need correcting– Structured– Semistructured– Ill-structured

• Problem Solving: the activity associated with changing the state of what “is” to what “should be”

7

Quality Problem Types

1. Conformance problems2. Unstructured performance problems3. Efficiency problems4. Product design problems5. Process design problems



Key Factors in Six Sigma Project Selection

• Financial return, as measured by costs associated with quality and process performance, and impacts on revenues and market share

• Impacts on customers and organizational effectiveness

• Probability of success• Impact on employees• Fit to strategy and competitive advantage



Problem Solving Process

1. Redefining and analyzing the problem2. Generating ideas3. Evaluating and selecting ideas4. Implementing ideas



Key Idea



A structured problem-solving process provides all employees with a common language and a set of tools to communicate with each other, particularly as members of cross-functional teams.

DMAIC Methodology

1. Define2. Measure3. Analyze4. Improve5. Control



Common Six Sigma Tools



Define

• Describe the problem in operational terms• Drill down to a specific problem statement

(project scoping)• Identify customers and CTQs, performance

metrics, and cost/revenue implications



Measure

• Key data collection questions

– What questions are we trying to answer?– What type of data will we need to answer the

question?– Where can we find the data?– Who can provide the data?– How can we collect the data with minimum effort

and with minimum chance of error?



Analyze

• Focus on why defects, errors, or excessive variation occur

• Seek the root cause• 5-Why technique• Experimentation and verification



Improve

• Idea generation• Brainstorming• Evaluation and selection• Implementation planning



Control

• Maintain improvements• Standard operating procedures• Training• Checklist or reviews• Statistical process control charts



Tools for Six-Sigma and Quality Improvement

• Elementary statistics• Advanced statistics• Product design and reliability• Measurement• Process control• Process improvement• Implementation and teamwork



Design for Six Sigma• Focus on optimizing product and process

performance• Features

– A high-level architectural view of the design– Use of CTQs with well-defined technical requirements– Application of statistical modeling and simulation

approaches– Predicting defects, avoiding defects, and performance

prediction using analysis methods– Examining the full range of product performance

using variation analysis of subsystems and components



Key Idea



All Six Sigma projects have three key characteristics: a problem to be solved, a process in which the problem exists, and one or more measures that quantify the gap to be closed and can be used to monitor progress.

Key Six Sigma Metrics in Services

• Accuracy• Cycle time• Cost• Customer satisfaction



Lean Production and Six Sigma

• The 5S’s: seiri (sort), seiton (set in order), seiso (shine), seiketsu (standardize), and shitsuke (sustain).

• Visual controls• Efficient layout and standardized work• Pull production• Single minute exchange of dies (SMED)• Total productive maintenance• Source inspection• Continuous improvement



Traditional Economic Model of Quality of Conformance



Total cost

Cost due to nonconformance

Cost of quality assurance

“optimal level” of quality100%

Modern Economic Model of Quality of Conformance



Total cost

Cost due to nonconformance

Cost of quality assurance

100%

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