Quality Function Deployment

R i c h a r d C o w a n , P h . D. , P. E .C h r i s t o p h e r S a l d a n a , P h . D.W o o d r u f f S c h o o l o f M e c h a n i c a l E n g i n e e r i n gG e o r g i a I n s t i t u t e o f T e c h n o l o g yA t l a n t a , G e o r g i a , U S A

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Phases of Design

CustomerUnderstand the Design Process

Specification DevelopmentSpecification of Information

Conceptual DesignSpecification of a PrincipleFunctional DecompositionGenerate ConceptsConcept EvaluationConcept SelectionPreliminary Design/Embodiment

Detail Design

Specification of ProductionProcess Planning

Manufacture

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● airlines

● passengers

● flight attendants

● pilots

● ground crew

● TSA

● air traffic control

● FAA

● and many others….

Who is the Customer for this System?

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● Focus Groups● One-on-One Interviews● Ethnography (culture)● Empathic design (feelings)● Many others...

Customer needs are found by asking, observing, and testing

https://www.coolcamping.co.uk/features/35-the-rise-rise-of-inflatable-tents

Lin, J., and Seepersad, C., 2007, “Empathic Lead Users: The Effects of Ex- traordinary User Experiences on Customer Needs Analysis and Product Rede- sign,” ASME DETC Design Theory and Methodology Conference, Las Vegas, NV, ASME, New York, Paper No. DETC2007-35302.

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Basic:• Expected or assumed (threshold attributes)• Typical of “invisible” products• Functions of products

Performance:• One dimensional• Most market research

Excitement:• Pleasant surprises or customer delights• Unexpected

Three Types of Quality/Features

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Customer needs are specific, positive, and solution-neutral

MIT OpenCourseWare: Thomas A. Roemer

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Question Customer Statement Interpreted Need ImportanceTypical uses • Independent use by student • Operable by person with

disabilities• (must) 4

Likes • Portable, Mobile• Auditory sound provided when page is

turned• Adjustable stand for different book sizes

• Portable• Signals when performing desired

actions• Adjusts to different book sizes

• (good) 3

Dislikes • Used so much that we wore it out• Heavy• Need consistent page turning

• Lightweight• Repairable by staff• Easily replaceable parts• Predictable page turning• Low failure rate• Long mean time between failures

• (good) 3• (good) 3• (must) 4• (must) 4• (should) 2

Suggested Improvements

• Built in delay for multiple button pushes• Be able to turn newspaper pages• Be able to turn scrapbook pages• Multiple students can share

• Turns variety of page types• Accounts for accidental, repeat

button pushes• Operable by multiple persons

• (should) 2• (good) 3• (must) 4

Customer Needs (e.g., Page Turner)

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From Customer Needs to Specifications

Engineering Requirements and Specifications Translate Voice of the Customer to Technology

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QFD is a design planning tool:• for translating customer needs into appropriate product development

requirements• that identifies the significant item(s) on which to focus time, product

improvement efforts and other resources

QFD enables:• the identification of important issues and items• the identification of trade-offs and synergies

Quality Function Deployment (QFD)

Supplier SupplierCustomer Customer

QFD

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• Design tool for coordinating design efforts towards goods customers WANT

• House of quality (HOQ) is part of QFD

• Focus on quality and customer needs across the design process and across corporate boundaries

• Guide design priorities based on customer needs and competitive benchmarking

• Over 70% of US companies use QFD (Ford, Xerox, Toyota …)

House of Quality (HOQ)

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Effect of QFD on Performance

HOQ Images from: Hauser, J.R., and D. Clausing, “The House of Quality,” Harvard Business Review, May/June 1988, pp. 63-73.

Changes = Money Earlier Changes = Less Money Spent

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Customer desires (qualitative)

House of Quality (HOQ)

Product performance (quantitative)

Specification is a:Metric with Target Value & unitsmass < 0.1 kg volume < 250 cm3

Customer Needs Engineering Requirements and Specifications

HOQ

HOQ Translates Needs to Specifications

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House of Quality (HOQ) components

(4) CENTERMetrics vs.

Customer Needs (relationships)

(5) BOTTOMMetric Targets

(engineering specification targets)

(3) CEILINGMetrics

(for customer need fulfillment)

(1) LEFTWeighted Customer

Needs

(6) TOPConflicts & Synergies

(2) RIGHTCustomer

Perceptions(of products &

concepts)

direction of improvement

• Customer needs/perceptions

• Engineering metrics/requirements• Targets

• Direction of improvement

• Conflict/synergies

• Relationship matrix

• Correlation matrix

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Customer needs/perceptions:• These are the ‘whats’• Assigned numerical importance (e.g., 1 to 10)

Engineering metrics/requirements:• These are the ‘hows’• Determine most important ones using Relationships• Determine synergies/conflicts with Correlations

Relationship matrix (RM):• Maps relationship between ‘hows’ and ‘whats’• Quantitative relationship levels (e.g., 1, 3 and 9)

Correlation matrix (CM):• Maps correlation between engineering requirements• Strong positive, positive, negative, strong negative

House of Quality (HOQ) components

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Relationship Matrix in HOQ

Engi

neer

ing

Requ

irem

ents

Customer Requirements (Explicit and

Implicit) adju

stab

le r

ange

of d

imen

sion

s

forc

e on

the

page

rate

of w

ear

of c

ompo

nent

s

# sp

ecia

lty c

ompo

nent

s

# to

ols

need

ed to

rep

air

gran

ular

ity o

f pag

e tu

rnin

g co

ntro

l

erro

r ra

te in

pag

e tu

rnin

g

▼ ▲

operable by person with disabilities

Portable/Mobile

Signals when performing desired actions

lightweight

repairable by staff

easily replaceable parts

num

ber

of a

ssem

bly

and

disa

ssem

bly

orie

erro

r in

alig

ning

par

ts

tole

ranc

e of

use

r-in

itate

d m

otio

ns

grip

forc

e re

quir

ed o

f ope

rato

r

tota

l mas

s

carr

ying

dim

ensi

ons

audi

tory

vol

ume

of s

igna

ls

mat

ch s

igna

ls w

ith u

ser

gene

rate

d ac

tion

inte

nsity

of v

isua

l sig

nals

predictable page turning

low failure rate

safely handles variety of reading materials

●

▽ ●

○○ ○

●● ● ●

●● ○

○ ●●

●○

●

▼▼ ▼Direction of Improvement ▲ ▼ ▼ ▲▼ ▼ ▼ ◇ ◇ ◇ ▼

what

how

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Correlation Matrix in HOQ

force on the page

tolerance of user-initated motions

grip force required of operator

total mass

carrying dimensions

auditory volume of signals

match signals with user generated actions

intensity of visual signals

mber of assembly and disassembly orientati

error in aligning parts

# specialty components

# tools needed to repair

granularity of page turning control

error rate in page turning

rate of wear of components

adjustable range of dimensions

+

−

erro

r ra

te in

pag

e tu

rnin

g

−

# to

ols

need

ed to

rep

air

gran

ular

ity o

f pag

e tu

rnin

g c

Column #

tole

ranc

e of

use

r-in

itate

d m

o

grip

forc

e re

quir

ed o

f ope

rato

tota

l mas

s

rate

of w

ear

of c

ompo

nent

s

adju

stab

le r

ange

of d

imen

sio

forc

e on

the

page

carr

ying

dim

ensi

ons

audi

tory

vol

ume

of s

igna

ls

mat

ch s

igna

ls w

ith u

ser

gene

inte

nsity

of v

isua

l sig

nals

num

ber

of a

ssem

bly

and

disa

erro

r in

alig

ning

par

ts

# sp

ecia

lty c

ompo

nent

s

Engineering requirements

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Target Values for Engineering Requirements

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Determine how specific values for engineering requirements influence satisfaction of customer needs

• Scientific studies • Survey tests• Focus groups• Refer to standards organizations

(NIOSH, OSHA, NIST, ASTM, etc)

Coffee grind example

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What• Hot• Taste/flavor• Smell• Stimulating• Aesthetics• Color• Cost• Grind• Not toxic

HOQ Example (e.g., Coffee)

How• Serving temperature (Hot)• Taste jury (Taste)• Smell jury (Smell)• Measure caffeine level

(Stimulating)• Jury (Aesthetics)• Color standard (Color)• Price (Cost)• Filter & weight (Grind)• Lethal Dose 50% (Median, LD 50)

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Cup of Coffee House of Quality (Filled)

Matrix Weights• Strong, = 9• Medium, = 3• Weak, ∆ = 1

• The 181 from column 1 comes from:

• The sum of the Absolute Importance row is:

• The 0.27 in the first column of the Relative Importance row comes from:

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181 132 54 99 18 108 90 682+ + + + + + =

181682

0 2654 0 27= ». .

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Look for:• Blank rows – unaddressed customer need• Blank columns – unimportant engineering

requirement• Communication opportunities• Sales Points – competitors strengths/features• Resolve or prioritize negative correlations• Final correct targets• Determining planned quality• What design requirements to be deployed to

Phase II (Parts Deployment)

Analyzing and Diagnosing the HOQ

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Summary – QFD/HOQCustomer requirements• Rank based on customer priority

Engineering requirements• Must be measureable (e.g., engineering units), have

improvement direction and a target value• Rate relationship to customer requirements• Relate tradeoffs with other engineering reqs.• Determine most important ones using calculation

Describing this figure in text• Describe chart’s contents, not what the chart is itself!• What is important for each set of data?• Use numerical information from figure

See Ch. 2 in book for detail, templates online