Chapter 5: Product Specifications

Product Design and DevelopmentFourth Edition

by Karl T. Ulrich and Steven D. Eppinger

Planning

Product Development Process

ConceptDevelopment

System-LevelDesign

DetailDesign

Testing andRefinement

ProductionRamp-Up

Remember that we are looking at an overall Product Development Process. We are going into more detail on Concept Development. We did a lecture, quiz and homework assignment on customer needs. Now we are ready to go to the next step in Concept Development.

Concept Development Process

Perform Economic Analysis

Benchmark Competitive Products

Build and Test Models and Prototypes

IdentifyCustomer

Needs

EstablishTarget

Specifications

GenerateProduct

Concepts

SelectProduct

Concept(s)

Set Final

Specifications

PlanDownstreamDevelopment

TestProduct

Concept(s)

DevelopmentPlan

Target SpecsBased on customer needs and benchmarking

Final SpecsBased on selected concept, feasibility, models, testing, and trade-offs

• Basic control and reference document for the design and manufacture

• Specific, measurable, testable criteria• “Unambiguous, Understandable, Correct, Concise, Traceable,

Traced, Design Independent, Verifiable, Unique, Complete, Consistent, Comparable, Modifiable, Attainable”

• Functional decomposition• Performance targets• Constraints (Demands, Musts)• Goals (Wishes, Wants)• Features

Product Design Specifications

The Blind Men and the ElephantA Hindu fable by John Godfrey Saxe from Elephants Ancient and Modern by FC Sillar and RM Meyler.

It was six men of IndostanTo learning much inclined,Who went to see the Elephant(Though all of them were blind),That each by observationMight satisfy his mind. The First approached the Elephant,And happening to fallAgainst his broad and sturdy side,At once began to bawl:`God bless me! but the ElephantIs very like a wall!' The Second, feeling of the tusk,Cried, `Ho! what have we hereSo very round and smooth and sharp?To me 'tis mighty clearThis wonder of an ElephantIs very like a spear!' The Third approached the animal,And happening to takeThe squirming trunk within his hands,Thus boldly up and spake:`I see,' quoth he, `the ElephantIs very like a snake.'

The Fourth reached out his eager hand,And felt about the knee.`What most this wondrous beast is likeIs mighty plain,' quoth he;`'Tis clear enough the ElephantIs very like a tree!' The Fifth who chanced to touch the ear,Said: `E'en the blindest manCan tell what this resembles most:Deny the fact who can,This marvel of an ElephantIs very like a fan!' The Sixth no sooner had begunAbout the beast to grope,Than, seizing on the swinging tailThat fell within his scope,`I see,' quoth he, `the ElephantIs very like a rope!' And so these men of IndostanDisputed loud and long,Each in his own opinionExceeding stiff and strong,Though each was partly in the right,And all were in the wrong! So, oft in theologic wars,The disputants, I ween,Rail on in utter ignoranceOf what each other mean,And prate about an ElephantNot one of them has seen!

Writing a good PDS is very difficult

• Customer• Regulatory Bodies• Laws of Physics• Functional Analysis• Company Constraints• Social, Political, and Legal Requirements

The Product Specs Process

• Set Target Specifications– Based on customer needs and benchmarks– Develop metrics for each need– Set ideal and acceptable values

• Refine Specifications– Based on selected concept and feasibility testing– Technical modeling– Trade-offs are critical

• Reflect on the Results and the Process– Critical for ongoing improvement

Product Specifications Example:Mountain Bike Suspension Fork

Start with the Customer Needs

# NEED Imp ST

Tritr

ack

Man

iray

2

Rox

Tah

x Q

uadr

a

Rox

Tah

x Ti

21

Tonk

a P

ro

Gun

hill

Hea

d S

hox

1 The suspension reduces vibration to the hands. 3 • •••• •• ••••• •• •••2 The suspension allows easy traversal of slow, difficult terrain. 2 •• •••• ••• ••••• ••• •••••3 The suspension enables high speed descents on bumpy trails. 5 • ••••• •• ••••• •• •••4 The suspension allows sensitivity adjustment. 3 • •••• •• ••••• •• •••5 The suspension preserves the steering characteristics of the bike.4 •••• •• • •• ••• •••••6 The suspension remains rigid during hard cornering. 4 • ••• • ••••• • •••••7 The suspension is lightweight. 4 • ••• • ••• •••• •••••8 The suspension provides stiff mounting points for the brakes. 2 • •••• ••• ••• •• •••••9 The suspension fits a wide variety of bikes, wheels, and tires. 5 •••• ••••• ••• ••••• ••• •

10 The suspension is easy to install. 1 •••• ••••• •••• •••• ••••• •11 The suspension works with fenders. 1 ••• • • • • •••••12 The suspension instills pride. 5 • •••• ••• ••••• ••• •••••13 The suspension is affordable for an amateur enthusiast. 5 ••••• • ••• • ••• ••14 The suspension is not contaminated by water. 5 • ••• •••• •••• •• •••••15 The suspension is not contaminated by grunge. 5 • ••• • •••• •• •••••16 The suspension can be easily accessed for maintenance. 3 •••• ••••• •••• •••• ••••• •17 The suspension allows easy replacement of worn parts. 1 •••• ••••• •••• •••• ••••• •18 The suspension can be maintained with readily available tools. 3 ••••• ••••• ••••• ••••• •• •19 The suspension lasts a long time. 5 ••••• ••••• ••••• ••• ••••• •20 The suspension is safe in a crash. 5 ••••• ••••• ••••• ••••• ••••• •••••

Met

ric #

Nee

d #s

Metric Imp Units1 1,3 Attenuation from dropout to handlebar at 10hz 3 dB2 2,6 Spring pre-load 3 N3 1,3 Maximum value from the Monster 5 g4 1,3 Minimum descent time on test track 5 s5 4 Damping coefficient adjustment range 3 N-s/m6 5 Maximum travel (26in wheel) 3 mm7 5 Rake offset 3 mm8 6 Lateral stiffness at the tip 3 kN/m9 7 Total mass 4 kg

10 8 Lateral stiffness at brake pivots 2 kN/m11 9 Headset sizes 5 in12 9 Steertube length 5 mm13 9 Wheel sizes 5 list14 9 Maximum tire width 5 in15 10 Time to assemble to frame 1 s16 11 Fender compatibility 1 list17 12 Instills pride 5 subj18 13 Unit manufacturing cost 5 US$19 14 Time in spray chamber w/o water entry 5 s20 15 Cycles in mud chamber w/o contamination 5 k-cycles21 16,17 Time to disassemble/assemble for maintenance 3 s22 17,18 Special tools required for maintenance 3 list23 19 UV test duration to degrade rubber parts 5 hours24 19 Monster cycles to failure 5 cycles25 20 Japan Industrial Standards test 5 binary26 20 Bending strength (frontal loading) 5 MN

Establish Metrics and Units

Additional Areas to Consider• Physical requirements• Functional requirements• Service environment (comprehensive: insect and bird

damage)• Kinematics – type of motion, direction, velocity,

acceleration• Forces - direction, magnitude, frequency, resonance,

stiffness• Materials – properties of final product, flow of

materials, design for manufacturing

Design Specification Checklist• Performance At what speed must it operate? How often will it be used (continuous or discontinuous use)?

How long must it last? • Environment (during manufacture, storage and use) All aspects of the product’s likely environment should

be considered: for example temperature, humidity, risk of corrosion, vibration. • Target product cost This is strongly affected by the intended market. • Competition What is the nature and extent of existing or likely competition? Does our specification differ

from the competition? If so, why? • Quantity and manufacture Should it be made in bulk, in batches, or as individual items made to order? Does

it have to be a particular shape? Can we make all the parts or must we buy some in? • Materials Are special materials needed? Do we have experience of working with the likely candidate

materials? • Quality and consistency What levels of quality and consistency does the market expect for this product?

Does every product have to be tested? • Standards Does the product need to conform to any local, international or customer standards? Is the

product safe? • Patents Are there any patents we may either infringe or register? • Packaging and shipping How will the product be packaged? How will the product be distributed? • Aesthetics and ergonomics Is the product easy and fun to use? Is it attractive to the right customer? • Market constraints Does a market already exist or must it be created? What is the likely product lifetime?

How long do we have to get the product to market? What are the customers’ likes and dislikes? • Company constraints Does the product fit in with company image? Are we constrained in material or

process choice? Are there any political considerations?

http://labspace.open.ac.uk/mod/resource/view.php?id=194654

More Things to Think About

• Production – Factory limitations, outsourcing, tolerancing (You may wait on actual tolerances until later – just think about the big picture.)

• Assembly• Transport• Costs• Schedule• Life-cycle issues• Human factors

Social, Political, Legal• Safety and environmental regulations• STANDARDS

– www.ul.com– www.outdoorindustry.com– www.cpsc.gov– www.astm.org– www.nfpa.org– http://www.nssn.org/

• Safety and product liability• Patents and intellectual property

Metrics Exercise: Ball Point Pen

Customer Need:The pen writes smoothly.

Link Metrics to Needs1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Need

Met

ricA

ttenu

atio

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m d

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ar a

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prin

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e-lo

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axim

um v

alue

from

the

Mon

ster

Min

imum

des

cent

tim

e on

test

trac

kD

ampi

ng c

oeffi

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ustm

ent r

ange

Max

imum

trav

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el)

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fset

Late

ral s

tiffn

ess

at th

e tip

Tota

l mas

s

Late

ral s

tiffn

ess

at b

rake

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ots

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dset

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re w

idth

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ass

embl

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e

Fend

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ompa

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still

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ide

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t man

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g co

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me

in s

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cha

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sem

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mbl

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nten

ance

Spe

cial

tool

s re

quire

d fo

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nten

ance

UV

test

dur

atio

n to

deg

rade

rubb

er p

arts

Mon

ster

cyc

les

to fa

ilure

Japa

n In

dust

rial S

tand

ards

test

Ben

ding

stre

ngth

(fro

ntal

load

ing)

1 reduces vibration to the hands. • • •2 allows easy traversal of slow, difficult terrain. •3 enables high speed descents on bumpy trails. • • •4 allows sensitivity adjustment. •5 preserves the steering characteristics of the bike. • •6 remains rigid during hard cornering. • •7 is lightweight. •8 provides stiff mounting points for the brakes. •9 fits a wide variety of bikes, wheels, and tires. • • • •

10 is easy to install. •11 works with fenders. •12 instills pride. •13 is affordable for an amateur enthusiast. •14 is not contaminated by water. •15 is not contaminated by grunge. •16 can be easily accessed for maintenance. •17 allows easy replacement of worn parts. • •18 can be maintained with readily available tools. •19 lasts a long time. • •20 is safe in a crash. • •

Benchmark on Customer Needs

# NEED Imp ST

Tritr

ack

Man

iray

2

Rox

Tah

x Q

uadr

a

Rox

Tah

x Ti

21

Tonk

a P

ro

Gun

hill

Hea

d S

hox

1 The suspension reduces vibration to the hands. 3 • •••• •• ••••• •• •••2 The suspension allows easy traversal of slow, difficult terrain. 2 •• •••• ••• ••••• ••• •••••3 The suspension enables high speed descents on bumpy trails. 5 • ••••• •• ••••• •• •••4 The suspension allows sensitivity adjustment. 3 • •••• •• ••••• •• •••5 The suspension preserves the steering characteristics of the bike.4 •••• •• • •• ••• •••••6 The suspension remains rigid during hard cornering. 4 • ••• • ••••• • •••••7 The suspension is lightweight. 4 • ••• • ••• •••• •••••8 The suspension provides stiff mounting points for the brakes. 2 • •••• ••• ••• •• •••••9 The suspension fits a wide variety of bikes, wheels, and tires. 5 •••• ••••• ••• ••••• ••• •

10 The suspension is easy to install. 1 •••• ••••• •••• •••• ••••• •11 The suspension works with fenders. 1 ••• • • • • •••••12 The suspension instills pride. 5 • •••• ••• ••••• ••• •••••13 The suspension is affordable for an amateur enthusiast. 5 ••••• • ••• • ••• ••14 The suspension is not contaminated by water. 5 • ••• •••• •••• •• •••••15 The suspension is not contaminated by grunge. 5 • ••• • •••• •• •••••16 The suspension can be easily accessed for maintenance. 3 •••• ••••• •••• •••• ••••• •17 The suspension allows easy replacement of worn parts. 1 •••• ••••• •••• •••• ••••• •18 The suspension can be maintained with readily available tools. 3 ••••• ••••• ••••• ••••• •• •19 The suspension lasts a long time. 5 ••••• ••••• ••••• ••• ••••• •20 The suspension is safe in a crash. 5 ••••• ••••• ••••• ••••• ••••• •••••

Benchmark on Metrics

Met

ric #

Nee

d #s

Metric Imp Units ST

Tritr

ack

Man

iray

2

Rox

Tah

x Q

uadr

a

Rox

Tah

x Ti

21

Tonk

a P

ro

Gun

hill

Hea

d S

hox

1 1,3 Attenuation from dropout to handlebar at 10hz 3 dB 8 15 10 15 9 132 2,6 Spring pre-load 3 N 550 760 500 710 480 6803 1,3 Maximum value from the Monster 5 g 3.6 3.2 3.7 3.3 3.7 3.44 1,3 Minimum descent time on test track 5 s 13 11.3 12.6 11.2 13.2 115 4 Damping coefficient adjustment range 3 N-s/m 0 0 0 200 0 06 5 Maximum travel (26in wheel) 3 mm 28 48 43 46 33 387 5 Rake offset 3 mm 41.5 39 38 38 43.2 398 6 Lateral stiffness at the tip 3 kN/m 59 110 85 85 65 1309 7 Total mass 4 kg 1.409 1.385 1.409 1.364 1.222 1.1

10 8 Lateral stiffness at brake pivots 2 kN/m 295 550 425 425 325 650

11 9 Headset sizes 5 in1.0001.125

1.0001.1251.250

1.0001.125

1.0001.1251.250

1.0001.125 NA

12 9 Steertube length 5 mm

150180210230255

140165190215

150170190210

150170190210230

150190210220 NA

13 9 Wheel sizes 5 list 26in 26in 26in26in

700C 26in 26in14 9 Maximum tire width 5 in 1.5 1.75 1.5 1.75 1.5 1.515 10 Time to assemble to frame 1 s 35 35 45 45 35 8516 11 Fender compatibility 1 list Zefal none none none none all17 12 Instills pride 5 subj 1 4 3 5 3 518 13 Unit manufacturing cost 5 US$ 65 105 85 115 80 10019 14 Time in spray chamber w/o water entry 5 s 1300 2900 >3600 >3600 2300 >360020 15 Cycles in mud chamber w/o contamination 5 k-cycles 15 19 15 25 18 3521 16,17 Time to disassemble/assemble for maintenance 3 s 160 245 215 245 200 425

22 17,18 Special tools required for maintenance 3 list hex hex hex hexlonghex

hex,pin

wrnch23 19 UV test duration to degrade rubber parts 5 hours 400+ 250 400+ 400+ 400+ 25024 19 Monster cycles to failure 5 cycles 500k+ 500k+ 500k+ 480k 500k+ 330k25 20 Japan Industrial Standards test 5 binary pass pass pass pass pass pass26 20 Bending strength (frontal loading) 5 MN 55 89 75 75 62 102

Metric Units Mar

gina

l Val

ue

Idea

l Val

ue

1 Attenuation from dropout to handlebar at 10hz dB >10 >152 Spring pre-load N 480 - 800 650 - 7003 Maximum value from the Monster g <3.5 <3.24 Minimum descent time on test track s <13.0 <11.05 Damping coefficient adjustment range N-s/m 0 >2006 Maximum travel (26in wheel) mm 33 - 50 457 Rake offset mm 37 - 45 388 Lateral stiffness at the tip kN/m >65 >1309 Total mass kg <1.4 <1.1

10 Lateral stiffness at brake pivots kN/m >325 >650

11 Headset sizes in1.0001.125

1.0001.1251.250

12 Steertube length mm

150170190210

150170190210230

13 Wheel sizes list 26in26in

700c14 Maximum tire width in >1.5 >1.7515 Time to assemble to frame s <60 <3516 Fender compatibility list none all17 Instills pride subj >3 >518 Unit manufacturing cost US$ <85 <6519 Time in spray chamber w/o water entry s >2300 >360020 Cycles in mud chamber w/o contamination k-cycles >15 >3521 Time to disassemble/assemble for maintenance s <300 <16022 Special tools required for maintenance list hex hex23 UV test duration to degrade rubber parts hours >250 >45024 Monster cycles to failure cycles >300k >500k25 Japan Industrial Standards test binary pass pass26 Bending strength (frontal loading) MN >70 >100

Assign Marginal and Ideal Values

Perceptual Mapping Exercise

Chocolate

Cru

nch

AlmondJoy

Plain M&Ms

PeanutM&Ms

KitKatOpportunity?

Now What? Can you get there from here?

• Make a functional model of the product• Make a technical model of the product• Make a cost model of the product• Refine the specifications, making trade-offs

where necessary.• Flow down the specifications as appropriate• Reflect on the results and the process.

Specification Trade-offs

.

Score on Monster (Gs)

Estim

ated

Mfg

. Cos

t ($)

50

60

70

80

90

100

110

120

3 3.2 3.4 3.6 3.8 4

Gunhill HeadShox

Tonka Pro

Rox Tahx Ti 21

Rox Tahx Quadra

Maniray 2

ST Tritrack

marginal values

ideal values

Score on Monster (Gs)

Trade-off Curvesfor Three Concepts

Estim

ated

Man

ufac

turin

g C

ost

($)

Set Final SpecificationsMETRIC Units Value

1 Attenuation from dropout to handlebar at 10hz dB >122 Spring pre-load N 6503 Maximum value from the Monster g <3.44 Minimum descent time on test track s <11.55 Damping coefficient adjustment range N-s/m >1006 Maximum travel (26in wheel) mm 437 Rake offset mm 388 Lateral stiffness at the tip kN/m >759 Total mass kg <1.4

10 Lateral stiffness at brake pivots kN/m >425

11 Headset sizes in1.0001.125

12 Steertube length mm

150170190210230

13 Wheel sizes list 26in14 Maximum tire width in >1.7515 Time to assemble to frame s <4516 Fender compatibility list Zefal17 Instills pride subj >418 Unit manufacturing cost US$ <8019 Time in spray chamber w/o water entry s >360020 Cycles in mud chamber w/o contamination k-cycles >2521 Time to disassemble/assemble for maintenance s <20022 Special tools required for maintenance list hex23 UV test duration to degrade rubber parts hours >45024 Monster cycles to failure cycles >500k25 Japan Industrial Standards test binary pass26 Bending strength (frontal loading) MN >100

Quality Function Deployment(House of Quality)

technicalcorrelations

benchmarking on needs

customerneeds

engineeringmetrics

target and final specs

relativeimportance

relationships between

customer needs andengineering metrics

Perceptual Mapping Quiz

Chocolate

Cru

nch

Name:______________________ CM:______Name:______________________