Session 4-Requirements-Function Diagram REV

Session 4- Requirements, QFD, Function Analysis

Donald E Malen, [email protected]

1 Successful Product Systems

2 Design Process

3 Definition: System

4 Identifying System Functions

5 Sorting Functions

6 Setting Function Requirements

Development of Design Requirements



Synonyms for Requirement; specification, criterion, objective, target

Requirement: That which is required or demanded

System Level Requirements: what is demanded of the whole product.

Subsystem Level Requirements: what is demanded from subsystems of the product.



Voice of customer

Product system requirements

Flow down of requirements

Subsystem requirements

Componentrequirements

CustomerAcceptance

Product systemtests

subsystemtests

Component tests

Flow Down of Requirements

Design PerformanceValidation



Voice of customer

Product system requirements

Flow down of requirements

Subsystem requirements

Componentrequirements

Example: Flow Down of Requirements

Brew in 3 minutes

“I want a fast cup of coffee”

Heater element will provide 100 BTU / minute

Transfer at least 90 BTU / minute to water

heat transfermodel

Our interest is to set Product system requirements



Need

Customer

functionsI need a quick cup of coffee

brew fast

Example-Coffer maker

Brew 6 cups in3 minutes

performed to a desired

level

Requirement

SystemCoffee maker

How do we know what numbers to use?

complaintshelps identify the most important function deficiencies of the current product

Kano catagoryhelps identify a function which would differentiate our product

Containing system mapwhat areas to research for needs/constraints



Market Place

Product Benchmarking

Manufacture & Distribute

CustomerUse

Customer will compare your redesigned product to others in the market place We need to set our requirement levels relative to competitive products

Product Benchmarking is the activity of investigating performance of competitive products

Designprocess



“My bike should be easy to pedal”

Benchmarking as an aid to set requirements

effort to pedal at 5 mph(low gear, flat road)

Need

System=bicycle

Functionsatisfied by

20 10 5

Benchmark Competitive bikes

Effort at pedal, (N)SchwinnHuffyToys R UsRaleigh

better

15



Set requirements by comparison to competitive performance

Just Acceptable Level

Best in Class Level

Our Requirement

?

range of performance today

Effort at pedal, (N) better

20 10 515



• Industry Status• Lateral Technologies• Kano category

Setting the requirement with respect to benchmarked Products

some helpful tools:



1885

chain and sprocket pedal drive is perfected

1876

spoke arrangement allows more torque to be applied

Evolution of an Industry

time1816

bicycle appears as novelty – you ran along to power

1863

many variants in powering using direct pedals, linkage to front or rear wheel

1870

an understanding of power matching begins

Measure of Product

Performance(Ease of

powering )



Novelty Dynamic Phase Static Phase

S Curve for an Industry

Measure of Product Performance

time

Evolutionary, Incrementalchanges can be predicted based on current performance

Innovative, Radical changes

better



Importance of Product Status to requirements

1. Which product attributes to emphasize during design depend on product status

2. Knowing the product status indicates whether future requirement levels need to be incremental improvements or large compared with today’s performance levels

3.If a product is known to be static it is possible to identify the extent of an innovation necessary to end the static plateau



Functional Performance

•Cost•Quality

Novelty

How to distinguish your product in the market place

•Fashion

competing products

Characteristics which will attract customer to your product



Ease of opening can Dynamic Phase Static Phase

1927

initial dynamic phase ended with

Invention by Ezra J. Warner 1858

1858

Evolution of an Industry – Can OpenerCanned food invented for British Navy in 1813Instructions to open can: Cut around the top edge with a chisel

Attracting customers with fashion in the

Static Phase

1867









Using Product Status in setting requirements

time

perfo

rman

ce

now

when the product now being designed will enter the market

where competitive

products are today

where competitive products will

probably be in future

Rate of improvement



Typical rate of improvementDynamic Product: 40%-100% per year

Moore's Law Gordon Moore, Intel Co-founder, 1965

Doubling of CPU capacity every 2 years


example:Computer

CPU capacity



Typical rate of improvement•Static Product: 0-10%/year


15171921

23252729

1975 1980 1985 1990 1995 2000 2005year

CA

FE m

pg

6%

0.2%

www.nhtsa.dot.gov

exampleCar fuel economy

Rate of improvement

set to increase in near future









time

Poor performance because we aren't very good at achieving the desired function

EitherThe product is ideal and meets customer needs completely

Beginning mastery of technology with rapid improvements

Industry S CurveUnderlying reason for curve

Industry Performance

forattribute or

there is a forced trade off in meeting two functions simultaneously and it is difficult to get better



Why a static plateau?A forced conflict in functions

Easy to slice lid

conflictingrequirements

Safe to use

Sharp edge

Bluntedge

trade-off



1927

Disruptive Innovation at System Level

New TechnologyNon exposed cutting edge

1923



Innovation Always Eliminates a Trade-Off forced by the Current Technology

Easy to slice lid

Non exposed cutting edge very sharp, yet user is protected

Safe to use

no conflictingrequirements

Can have both in same product



A New Static Phase but with better performance

1927today



A New Static Phase but with better performance

innovation innovationtime

performance

technology 1

technology 2

technology 3


CustomerUse

Designprocess

Market place

Perfect competition delivers products with ever increasing levels of performance



1962–1965

West GermanyGM Opel Kadett

1965–1973

1973–1979

1979–1984

1984–1991

1963 1991

East GermanyTrabant


CustomerUse

Designprocess

Market placePerfect Competition delivers

products with ever increasing levels of performance

Without the driver of Perfect Competition, products become truly static

The S curve is not a law of nature



Identifying Product StatusQuestionnaire

Two pages of Yes/No questions; Total the answers for both pages to get indication of product status

• Has there been a technical advance recently that may be used to replace this product?

• Do most companies making this product appear to copy each other?

• Must new designs use the existing production facilities?



time

perfo

rman

ce

now

where competitive products are

today

when the product now

being designed will enter the

market

where competitive products will

probably be in future

future

now

better

Just Acceptable Level today

Best in Class Level today

Pedal effort(N)

10 520



CustomerUse

Market Place

Designprocess

Design Lead Time



Where to get data for benchmark data




• Product Status• Lateral Technologies

looking at how a function is provided in other industries

• Kano category



Blending time (min)0.53

Delightful

Lateral Technologies may show the way to improved performance not seen in competitive products

Competitive product

Lateral Product/ Technology

Industrial grade chemistry lab blender

Lateral means something performing a similar function, but outside of the industry our product is in.

Blender



www.delphion.comalso Google patents

sources for lateral technology

patents

www.google.com

image search

search on function




• Industry Status• Lateral Technologies• Kano category



Just AcceptableLevel

Kano Category use in setting requirements

betterBest in

Class Level

Expected

Normal

Delightful

• Meet minimal acceptable level within competition• No value in overachieving• Trade-off attribute level if in conflict with a Delightful or Normal function, but do not go below minimal level

•Provide greater functionality than competition•Compromise other functions in trade-off conflict with this function•Do not lose focus on the function during design (include in mission)

•Use Brand identity to determine which normal functions to set high•Trade-off attribute level if in conflict with a Delightful function•All Normal functions need to be competitive

Constraint•Meet minimal acceptable level•If in conflict with a Delightful function, verify need for constraint



Using all the tools to set the requirementContaining system function, Kano category, Benchmarking,

Lateral Technology, Product Status

Blending time (min)

Competitive Products

future performance based on industry status(static industry, 1 year design lead time)

Our Requirement

Delighting function

Lateral Product

Still a judgment, but a data driven judgment

better



Documenting Requirements

• Product Design Specifications—PDS Documenting the requirements

• QFD



The PDS is very conveniently created on Excel. This allows

•sorting based on Kano Category, Interacting System, Constraint/Need

•graphing benchmarked levels

•tracking actual performance during design

Attribute / Function units

interactingsystem

constraint or

needKano

category

Product Design Specification - PDS

2.5

0.7

<300-constraintkitchen counter

mm

1.51.52.0normalneedcustomer litervolume blended

Delightfulneedcustomer 0.91.50.5MinutesBlend Time

Total height

smaller bettertargetbettersmallerbetter

req’m’ttype



Project Example- Product Design Specifications

more pages



more pages

Project Example-Product Design Specifications



... be directly related to a function ... be directly related to a function

• either a customer need or constraint

... be as solution-neutral as possible ... be as solution-neutral as possible

• use system thinking; relate to functions not parts

... be prioritized ... be prioritized

• constraint or Kano catagory

Every requirement should Every requirement should

Final check on requirements

... be suitable to be used for the evaluation of a solution ... be suitable to be used for the evaluation of a solution

• quantified, clear formulation



Containing system analysis•Brew coffee•Look good on counter•easy to clean

Relationship of tools for product planning

Product Design Specification(PDS) norma

lneedcustom

erlitervolu

meblended

Delightful

needcustomer

.7.91.5

.5Minutes

Blend Time

Document the results of the product planning phase.

What functions does the product need to provide—to the customer, for the constraints?

Blending time (min)0.53 1

Delightful

TargetBenchmarking•Industry•Lateral

What level of performance is seen in the market today?

Like

Like

Normal

Don't Care

Don't Like

Care LikeNormal Don'tDon't

Normal

Expected

Delightful

KanoCustomer complaints andKano analysis

What are the most important functions?

SStatic/Dynamicproduct status

Industry S curve What level of performance will be seen in the market when our redesigned product is available?What will differentiate out product?

Tool Purpose



Product Design Specification

Relationship of ToolsRequirements Capture

Containing System Map

•Brew coffee•Look good on counter•easy to clean

•Braun

•Krupps

•Celestial Seasons Tea

time

perf

dynstatic

Product Status

Fuel Economy (mpg)

35 4025X

Benchmarking

normalneedcustomer litervolumeblended

Delightfulneedcustomer .7.91.5.5MinutesBlend Time

Attribute/Function units

interactingsystem

constraint or

needKano

category

KanoCatagory

Like

Like

Normal

Don't Care

Don't Like

Care LikeNormal Don'tDon't

Normal

Expected

Delightful

Kano



Documenting the results of the product planning phase

• Product Design Specifications• QFD a brief review



Number of Design Changes

Time(months)Enter

Market

Typical US company1990

Japanese company1990

Fast to marketQuality at start up

HOW?

EnterMarket



"The foundation of the house of quality is the belief that products

should be designed to reflect customer's desires and tastes.

Marketing people, design engineers, and manufacturing staff must

work closely together from the time a product is first conceived."

The House of Quality, Hauser and Clausing

Quality Function Deployment



Customer attributes

3

Tim

e to

bre

wm2 m cups

Quality Function Deployment Matrix-Example

importance to customer

Engineering Characteristics

sec

requiredcurrent

competitor #1competitor #2

Performance

3020025050

0.70.70.60.8

0.30.20.40.5

4652

Brew Coffee Fast

Fit well on kitchen counter

Makes enough coffee

1

2

Foot

prin

t siz

e

cups

bre

wed

heig

ht



•Customer Attributes

•need importance

QFD Structure-Customer Attributes

higher number more important

Customer attributes are the needs the customer wants in the product expressed as the 'voice of the customer'

Brew Coffee Fast


Makes enough coffee

3

1

2



•Engineering Characteristics

QFD Structure-Engineering CharacteristicsEngineering Characteristics are objective, quantifiable

measures for product performance; you can measure in the lab

Tim

e to

bre

w

Foot

prin

t siz

e

heig

ht

cups

bre

wed

sec m2 m cups•Units



QFD Structure-C.A. to E.C correlations in matrix

Customer Attribute-to-Engineering Characteristic correlation

Strength of relationshipHigh =9Medium =3Low =1

Customer attributes

Brew Coffee Fast


Makes enough coffee

Tim

e to

bre

w

Foot

prin

t siz

e

heig

ht

cups

bre

wed




Engineering Characteristic benchmarking

QFD Structure-Engineering Characteristic Benchmarking

Tim

e to

bre

w

Foot

prin

t siz

e

heig

ht

cups

bre

wed

sec m2 m cups

current product competitor #1competitor #2

20025050

0.70.60.8

0.20.40.5

652

Units




QFD Structure-Requirements

Requirement for each engineering

characteristic

Tim

e to

bre

w

Foot

prin

t siz

e

heig

ht

cups

bre

wed

sec m2 m cups

required 30 0.7 0.3 4




Relationship of ToolsRequirements Development

Containing System Map

customer Needs=Customer Attributes

•Kano Sorting•Mission Statement

•Complaining listImportance

Benchmarking

smooth blend 0.53 1Delightful

Target

Competitive Products

Functions=Engineering Characteristics

normalneedcustomer

litervolumeblended

Delightful

needcustomer

.7.91.5.5Minutes

Blend Time

Product Design Specifications

Eng. Char. requirement



What Engineers count


Engineers can quantify and measure many thingsbut

Not everything that is countable counts

What Matters Voice of the customerCustomer Attributes

make sure what you are measuring relates to something the customer cares about



Engineering Measurement for Rocker Size

VehicleDiameter of

circumscribing circle, inches

Hudson 4.0

Rambler 3.5

Datsun 2.8

Nash 3.2

Studebaker 2.9

Was there a relationship of this measurement to Voice of the customer?

“I want a Solid ride”“I want a car that can take some abuse”“I want a safe car”

NoNoNo



Beware!

1. QFD requires DATA.-Avoid just capturing your own opinions-Use data from

-Containing system map-Customer complaint list-Kano categories-Mission Statement-benchmarking-both industry and lateral-S curve

2. Excessive detail is not helpful.Wall size charts with hundreds of rows are less effective than one with the essential 7-12 functions (precious few)

3. Not every thing that is countable counts.QFD can invite meaningless quantification, especially in quantifying the Customer Attribute importance

4. QFD is focused on voice of the CUSTOMER. The product must also meet CONSTRAINTS



productplanning

detail design

embodimentdesign

understand customer needs

andconstraints

Use of Requirements

conceptualdesign

requirements PDS

1

2

3

4

to create product concepts

to select best concept

to optimize parameters

to validate final design



Development of Design Requirements1 Successful Product Systems

2 Design Process

3 Definition: System

4 Identifying System Functions

5 Sorting Functions

6 Setting Function Requirements• Product Design Specifications• QFD

7 Defining Subfunctions – Function Diagram



ConceptualDesign

ProductPlanning


andconstraints

requirements PDS

Functions (actions)

product concepts (things)

Function Diagram shows what needs to be accomplished without referring to how to accomplish it

Function Diagram

Function Diagram encourages seeking new ways to satisfy customer needs over those currently used in the product



Example Function Diagram– Display Time

energy

signal

time

inputs outputsenergymaterialsignal

energymaterialsignal

System

Displaytime of

day

power

generate periodic signal

accumulate signal count

transform count to time of day

display time signal

store power



energy

signal

time

power




display time signal

store power

Pendulum Clock Design Concept

pendulum ratchet mechanism

gear train rotating hands

dropping weight

lift weight




energy

signal

time

power




display time signal

store power

Wind up Wrist Watch Design Concept

torsional spring/wheel

ratchet mechanism

gear train rotating hands

torsional main spring

wind up stem




energy

signal

time

power




display time signal

store power

Digital Watch Design Concept

quartz oscillator

digital circuit

LCD controller

LCD

batterychargebattery




radiation from sun

energy

signal

time




display time signal

store power

rotation of earth

shadowgraduated pattern

Position of sun

Example Function Diagram– Display TimeSun Dial Design Concept



Function Diagram



The properties of a signal;•detection of some physical condition in the product or surroundings•creation of information about what is detected•changing the state of the product based on this information

Definitions: energy, material, signal



Function diagram constructionThe purpose:

Step away from the current physical parts of a product and look instead at the functions being performed.

To make a function diagram:

1) Identify the main function of the product

2) Determine the steps needed to perform this main function. These are all actions not physical things. The steps are the sub-functions.

After completing the diagram, test its validity on the current product design. Can you map each part to a sub-function ?

Using the diagram:

With a valid function diagram, you can consider alternative hardware to perform the sub-functions and meet the design mission better.





Function – Blend contents

Function Diagram ExampleBlender

System



Function – Blend Contents

accept power

convert power to motion

mixing motion

chopping motion

energy

materialaccept contents

contain contents

signal control the type of motion

dispense contents

materialraw foodliquidice

blendedcontents

controls

chop and mix contents

signalindication of completion



System

Blendcontents



Function DiagramPotato Harvesting Machine

Energy

Potatoes in the ground

Signal

Harvest potatoes

Potatoes harvestedPotatoes rejectedLeavesSoil and dust

Jongwon Kim, Seoul National University



Jongwon Kim, Seoul National University



energy

material

signal

material

signal

Function Diagram-Flow FormatFormat useful when actions occur serially



Clean Clothes

Function Diagram-Hierarchy Format

Contain Cleaning

Fluid

Agitate Clothes

Heat Cleaning Process

Control process time and degree

Format useful when several actions must occur simultaneouslyor if product has several states-of-use

Washing machine exampleOrdering --1. Function, 2. Subfunctions to accomplish function, 3. Sub-subfunctions to accomplish subfunction

CleanTIme

FluidTemp

AgitationLevel

WaterLevel



Umbrella

Function Diagram-Hierarchy Format

Collapsefor storage

Coveruser

Umbrella Example- Two states-of-use

provideholder

SupportcanopyActuateLock

Closeddivertrain



How will the Function Diagram be used



Store Nails

IsolateNail

Sensetrip

TriggerTool

Convert energy to translational energy

Store or accept external energy

Apply Translational energy to nail

Nails

Trip of tool

Energy

DrivenNail

How will the Function Diagram be used



Using the function diagram to create design concepts

Convert ElectricalEnergy to

Translational Energy

ApplyTranslational

Energy to Nail

Alternative Working Principlesto accomplish subfunctions

we are beginning to identify hardware which accomplishes the function but is not limited to current product



productplanning

detail design

embodimentdesign


andconstraints

Pahl/Beitz: Engineering Design

Concept Design Phase

conceptualdesign

to create many design alternatives

to analyze design alternatives

to select the best design alternative

Documents

Session 4-Requirements-Function Diagram REV