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Six Sigma vs. Design for Six Sigma (DFSS). Dr. Suresh C. Rama Senior Manager, Quality Systems Global Engine Manufacturing Alliance (GEMA) Dundee, MI. Presentation Overview. Introduction to Quality Defining Quality Measuring Quality Six Sigma Method Tools Design for Six Sigma Method

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six sigma vs design for six sigma dfss

Six Sigma vs. Design for Six Sigma (DFSS)

Dr. Suresh C. Rama

Senior Manager, Quality Systems

Global Engine Manufacturing Alliance (GEMA)

Dundee, MI

presentation overview
Presentation Overview
  • Introduction to Quality
    • Defining Quality
    • Measuring Quality
  • Six Sigma
    • Method
    • Tools
  • Design for Six Sigma
    • Method
    • Tools
  • Implementation Enablers
  • Challenges

What are these companies have in common?






defining quality
Defining Quality
  • A study asking Managers from 86 firms in the U.S. to define quality produced several responses including:
    • Perfection
    • Consistency
    • Eliminating Waste
    • Speed of Delivery
    • Compliance to procedures, specifications, etc.
    • Providing good and usable product
    • Doing it right the first time
    • Delighting or pleasing customers
    • Total customer service and satisfaction

Extracted from “The Management and Control of Quality”, by Evans and Lindsay

defining quality5
Defining Quality
  • Quality is many things to many people in many parts of the organization
  • Quality can be defined based following criteria:
    • Judgmental Criteria
      • Goodness/Excellence of a Product/Image
    • Product-Based Criteria
      • The More the Better
    • User-Based Criteria
      • Fitness for intended use
    • Value-Based Criteria
      • Relationship to usefulness/satisfaction to price
    • Manufacturing-Based Criteria
      • Conformance to specifications

Extracted from “The Management and Control of Quality”, by Evans and Lindsay

integrating perspectives on quality
Integrating Perspectives on Quality
  • David Garvin’s 8 principle quality dimensions
    • Performance
    • Features
    • Reliability
    • Conformance
    • Durability
    • Serviceability
    • Aesthetics
    • Perceived Quality

Extracted from “The Management and Control of Quality”, by Evans and Lindsay

quality as a strategy
Quality as a Strategy
  • Competitive Advantage: Firm’s ability to achieve market superiority.
  • Wheelwright’s 6 characteristics for sustained competitive advantage:
    • Driven by Voice of the Customer
    • Contributes to successful business
    • Uses resources effectively
    • Difficult for competitors to copy
    • Basis for continuous improvement
    • Motivates the entire organization
  • Does Quality play a role in any of these characteristics?

Extracted from “The Management and Control of Quality”, by Evans and Lindsay



Lower Spec


Upper Spec






Measuring Quality-Quality and Sigma

  • “Quality” is the degree of excellence of a product, process or service from the customer’s viewpoint
  • Virtually every activity has variation - if the outcome is too far from the target value (beyond a specification limit), a defect occurs
  • Standard deviation, s,is a measure of variation from the target
  • Sigma Level, Z, of a process is:

(Spec Limit - Target)

Z =

Std Dev s

  • Sigma Level measures the probability of achieving a defect-free outcome

Sigma Level = 3

what is 6 sigma

Allowable Process Mean Shifts with time


Design Target)

Lower Specification Limit

Upper Specification Limit




What is 6 Sigma?
  • Common definition: 3.4 defects / million opportunities
  • Applicability: All business processes (Manufacturing , IT, Finance, Marketing)

** Waste due to additional inspection, tests, rework, scrap, customer dissatisfaction, etc. (Source: “Six Sigma” by Mikel Harry)

benefits of 6 sigma
Benefits of 6 Sigma


Sigma Level

Defects Per Million

Cost % of Sales




25 - 40%



15 - 25%



5 - 15%



< 1%

Savings (3 to 4.7 Sigma): $250K per project

Benefits (4.7 to 6 Sigma): Greater market share

Savings Realized



$750M (‘98), $1.5B (‘99)


$800-$900M / year ($15B over 11 years)


$900M / year

Allied Signal:

$500M (‘98), $600M (‘99)

* Waste due to additional inspection, tests, rework, scrap, customer dissatisfaction, etc.

Industry Week


Quoted savings from the book “Six Sigma” by


Harry & Richard Schroeder; Allied Signal quote from

the 6 sigma method of quality improvement
The 6 Sigma Method of Quality Improvement
  • Structured, data-driven problem-solving method
    • “DMAIC”: Define, Measure, Analyze, Improve,Control
    • Based on statistics, process analysis and process control
  • Developed by Motorola; used successfully by TI, AlliedSignal, GE, ...
  • Goal: improve the quality of existing processes
    • Manufacturing, business transactions, etc
  • Payoffs:
    • Internal productivity improvement (lean processes)
    • Capacity gain (lean resource management)

Six Sigma: driver for cost savings

how does 6 sigma work
How does 6 sigma work?
  • Visualize and Develop a Goal
  • Obtain a Coach/Mentor
  • Set the right Metrics
  • Understand the relationships between influencing factors (x)s and the effects/output (y)s. y = f(x)
  • Create a standradized process that develops a roadmap to the Goal
  • Now identify and implement the right Tools

Implementing Tools without the right Process, Strategy and Goal

the 6 sigma focus
The 6 Sigma Focus
  • Many quality approaches focus on inspecting and fixing outputs (e.g., products)
  • Six Sigma focuses on fixing and controlling key process variables which cause output defects

Output Y = f (Process Variables x1, x2, …, xn)

  • x’s
  • Inputs
  • Root Causes
  • Problems
  • Fix & Control
  • Y
  • Output
  • Effect
  • Symptom
  • Monitor
the 5 sigma wall


Redesign Benefit

“5s Wall”




Process Improvements

Plus Product Redesign to Match

Improved Process Capability


Process Improvements Only



The “5 Sigma Wall”

Break through the “5s wall” by redesign for manufacturability

can 6 sigma be applied to engineering
Can 6 Sigma be applied to Engineering?
  • It is difficult to apply classic Six Sigma to Engineering for new products
    • Engineering focuses on innovation, not process improvement
    • Defect baselines not known for new, innovative designs
  • And, most major new product quality problems are in performanceand reliability, not manufacturability
  • Engineering should focus on preventing problems
  • Need Six Sigma extension to new product creation “Design for Six Sigma” - DFSS!
6 sigma vs design for six sigma

Minimize variation (sigma) by process capability improvement

Minimize sensitivity to variation by choosing good nominal values for Xs

6 Sigma vs. Design for Six Sigma

Traditional 6-Sigma - Reactive

Design for Six Sigma - Proactive

what is design for six sigma dfss
What is Design For Six Sigma (DFSS)?
  • Design for Six Sigma (DFSS) is a strategy, a concept, a process and a set of tools
    • Strategy: To develop new and better products/processes to address the “voice of the customer”
    • Concept: To drive robust engineering (product & process) and validation with focus on “problem prevention.”
    • Process: To translate “voice of the customer” to engineering requirements and optimize the relationship between influencing factors and their effects on customers to achieve and sustain high quality levels.
    • Tools: Enablers for execution of the process to align with the “strategy.”
dfss strategy revolutionize design engineering


  • Quality “TESTED IN”
  • Evolving product design requirements
  • Product team specific design process
  • Focus on components and subsystems
  • Performance assessment by “build and test”
  • Performance & manufacturability problems fixed during and after launch
  • Difficult system integration
  • To
  • Quality “DESIGNED IN”
  • Customer focused design requirements
  • Disciplined and standardized design process
  • Focus on system level designs and functions
  • Performance predictions using analytical methods
  • Designed up-front for robust performance & manufacturability
  • Easier system integration
DFSS Strategy: Revolutionize Design & Engineering


Design Quality


Design Quality






dfss process

Select Projects based

on Quality indicators

and gap to targets



Verify predicted

Quality and


Verify &






Translate Voice of

the Customer to

Design Requirements



Optimize Quality,

Reliability and Durability

and improve Robustness

Develop, select and

synthesize concepts

for better designs

DFSS Process



D. F. S. S.

key dfss tools
Capture Voice of Customer & Define Eng. Requirements

Wants & needs tools

Customer use observations

Kano Analysis

Quality Function Deployment (QFD)

Develop Concepts and Select

Pugh Matrix

Axiomatic Design


Failure Mode & Effects Analysis (FMEA)

Develop Detailed Design

Systems Engineering

Function Models & FMEAs

Transfer Functions

Statistical Design

Monte Carlo Analysis

Design for Robust Performance

Design of Experiments

Robust Design

Design for Reliability

Design for Manufacturability

Process Capability Databases

Statistical Tolerancing

Predict Quality

DFSS Scorecards

Key DFSS Tools
fmea pro active quality tool

Right Execution

FMEA: Pro-Active Quality Tool
  • Purpose of a FMEA:
  • Risk Reduction to Customer(s)
    • End user
    • Manufacturing/Assembly
    • Service
  • Risk Reduction to comply with or exceed Government Regulations
    • Safety
    • Regulatory

Risk Reduction



key successful factors for dfss implementation
Key Successful Factors for DFSS Implementation
  • Develop a strategy that fits the culture
  • Obtain true leadership from the top
  • Execute flawlessly (ownership & accountability)
  • Create a mentoring infrastructure (x-functional)
  • Communicate results early and often
  • Make it a way of doing business (integration)
implementation challenges
Implementation Challenges
  • Technical
  • Paradigm change
    • Statistical versus deterministic
  • New methods and tools
    • Systems engineering
    • Design of experiments
    • Robust design
    • Design for reliability
    • Statistical tolerancing
    • Multi-variable optimization
    • ...
  • Cultural
  • Resistance to change:
    • “Why change our design process?”
    • “We’re different”
    • “We already do that”
  • Cost and disruption of training
  • Fear that design cycle times will be longer, costs higher
  • Integrating DFSS with existing development processes

Leadership must overcome them

message from leadership
Message from Leadership
  • DFSS must become a religion
  • Be an embodiment of 6 sigma (be competent)
  • Radiate (train and spread) DFSS into every business/organization
  • Be a lunatic on the subject (drive it hard)
  • Conduct DFSS reviews in the field
  • Set goals based on 6 sigma metrics
  • You have my full support to be outrageous on this issue

What are these companies have in common?

All of them use Design for Six Sigma - effectively

making six sigma dfss successful
Making Six Sigma/DFSS Successful
  • Leadership from the top is crucial
    • Clearly communicate the Quality vision
    • Demand Quality
    • Drive discipline
  • Drive Quality by measurable, “stretch” goals
    • Alignment of employee goals to organization’s goals
    • Six Sigma & DFSS are not a “cure-all” for Quality by themselves
  • Involve everyone
    • Don’t leave Quality to “quality specialists and professionals”
    • Train everyone in basic Six Sigma/DFSS competence
  • Regard Quality as a cultural change, not just a toolset
    • Make Quality a part of the organization’s DNA
thank you