designing and manufacturing consumer products for...

Designing and manufacturing consumer products forfunctionality a literature review of current functiondefinitions and design support tools

Wen-Chuan ChiangIndustrial Engineering University of Cincinnati Cincinnati OH USAArunkumar PennathurMechanical and Industrial Engineering University of Texas at El Paso TX USAAnil MitalIndustrial Engineering University of Cincinnati Cincinnati OH USA

1 Introduction

There are numerous products that are

marketed as being sophisticated in terms of

features they provide consumers but

routinely fail to perform the intended

functions or do so in a very unsatisfactory

manner For instance the Eastman Kodak

Companyrsquos disk camera was marketed as

being a usable camera with nearly 50

usability features However due to the

excessive noise in the output signal and its

related negative effect on the quality of the

pictures the camera took the Kodak disk

camera was considered a failure the camera

failed to provide the very basic intended

function plusmn ie taking good or even acceptable

photographs Another example is the

ubiquitous can opener found on supermarket

shelves To cut the lid the cutting edge in the

can opener has to progress around the lid and

sever it completely and cleanly without

leaving slivers of metal behind However

this seldom is the case in most can openers

(mechanical devices) In addition to not

performing the main function most can

openers jiggle the lid and cause it to splatter

or submerge the lid in the liquid as the cutter

progresses around the can

In Figure 1 we provide several examples to

show that functionality in can openers is

routinely not ensured In Figure 1a the can

opener has only a single cutting point and

the cutting edge is not sharp The can opener

in Figure 1b is a better design and provides a

better cutting edge than the one in Figure 1a

plusmn the round shape enables random selection

of the cutting point and hence longer life The

can opener in Figure 1c is similar in design to

the can opener in Figure 1b but the design

uses gears to ensure that the cutting edge will

be continuously rotated hence providing

longer blade life The can opener depicted in

Figure 1a uses a single joint (one rivet) and

the one in Figure 1b uses two rivets (one is in

the fixed style while the other is in the open

slot) hence the structural rigidity of the can

opener in Figure 1b is much higher than the

can opener in Figure 1a The crank designs in

can openers in Figure 1b and 1c are better

than the can opener in 1a because these

designs provide more rigidity and ease of

handling than the can opener in 1a The can

opener in Figure 1d is very different from the

ones in 1a b and c as it cuts the can from the

side so the lid will not drop into the food

From Figure 1 and other similar day-to-

day experiences we can conclude that while

providing functionality in a product may be

the design goal designers routinely fail to

ensure it in the product prototype

An understanding of the key elements

involved in the design and manufacturing of

consumer products for functionality and the

tools used to model functionality should help

shed light on why functionality is not

ensured in products Is the definition of

functionality adequate Are the current

criteria for product functionality adequate

Or is it a lack of close correspondence

between a productrsquos design and its

manufacturing These are some of the issues

addressed in this review paper The objective

is to critically examine the literature (both

research and practitioner literature in

design manufacturing mechanical systems

design and consumer product design) with

the focus on why products fail to provide an

intended and designed function

This paper is organized into the following

sections In section 2 a brief review of the

evolution and history of product design is

presented Beginning with some of the

earliest design goals such as Design for Cost

through some latter day design goals such as

Design for Safety and Design for Usability

the present day Design for X paradigm is

briefly discussed in this section Section 3

examines the different and widely used

definitions for product function and

Thecurrent issueandfull text archiveof this journal is available at

httpwwwemerald-librarycom ft

[ 430]

Integrated ManufacturingSystems126 [2001] 430plusmn448

MCB University Press[ISSN 0957-6061]

KeywordsProduct design Manufacturing

AbstractExamines the product design and

manufacturing literature tounderstand why consumer

products of daily use often fail toprovide the intended function tousersrsquo satisfaction The review

shows that the bulk of publishedliterature addressing functionalityand functional representation

deals with mechanical systemsdesign and there are issues thatdirectly affect the consumer that

are yet to be accommodated incurrent research in functionalrepresentation The literature also

reveals that very few of theproduct design support systems

have been tested on real designcases or have been developed andtested using real designers in

manufacturing environments plusmn thisissue needs serious consideration

if efficient designer aids are to bedeveloped in the future Alsothere is relatively little that hasbeen done to develop tools to

evaluate alternative designsolutions It is also apparent fromthis review that the main research

focus has been on providingfunction rather than on ensuring

function in a product that iseventually manufactured

Received September 1999Revised June 2000Accepted July 2000

functionality with examples for each

definition A review of the different models to

represent function and the existing tools to

provide functionality follows It should be

noted that the preponderance of published

literature in the functionality and functional

representation areas is on mechanical

systems design relatively very few articles

are in the manufacturing engineering

domain Also research on mechanical design

in specific technical domains such as

mechanisms and heat exchangers is beyond

the scope of this paper Section 4 provides

recommendations for further research

Section 5 presents an example to show how to

ensure product functionality and illustrates

potential linkages between functionality

criteria and manufacturing variables for a

can opener

2 Design goals history andevolution

Historically a variety of factors both

internal and external to a company have

influenced its product design goals For

Figure 1Various types of can openers

[ 431 ]

Wen-Chuan ChiangArunkumar Pennathur andAnil MitalDesigning and manufacturingconsumer products forfunctionality a literaturereview of current functiondefinitions and design supporttools


instance the mass production paradigm

pioneered by Henry Ford resulted in

concepts of building products in assembly

lines use of interchangeable parts and

standardization of parts and components

with a view towards reducing product cost

(Bralla 1996 Cross 1989 Green 1956 Lacey

1986 Ziemke and Spann 1993) Customersrsquo

demand for quality products prompted

manufacturing companies to consider

quality as their key product design goal

(Akiyama 1991 Taguchi et al 1989) The

establishment of the US Consumer Product

Safety Commission in 1972 prompted

manufacturers to project product safety as

their key design goal (Brauer 1990 Hammer

1980 Mital and Anand 1992) The advent of

the computer screen and the resulting digital

interface may be considered the primary

reason for companies projecting product

usability as their prime product design goal

(Nielsen 1993) Similarly the need for

product manufacturers to reduce assembly

time and cost have prompted product designs

built from design for assembly processes

(Bakerjian 1992 Boothroyd and Dewhurst

1983 Boothroyd 1994 General Electric

Company 1960 Gupta and Nau 1995 Kusiak

and He 1997 Miyakawa and Ohashi 1986

Miyakawa et al 1990 Nof et al 1997

Runciman and Swift 1985 Taylor 1997)

Recent legislation from the US

Environmental Protection Agency (EPA) has

prompted companies to project Design for

Environmental Friendliness or Green Design

as an important product design goal (Billatos

and Nevrekar 1994 Hermann 1994 Hundal

1994 Van Hemel and Keldmann 1996) Ford

Motor Company recently set up a facility for

disassembling used cars and selling used

parts (an Internet junkyard) profitability of

which will depend upon designing products

for disassembly (Wall Street Journal 1999)

Simultaneous optimization of a number of

design goals (Design for ` Xrsquorsquo) where X could

stand for assembly manufacturability

safety reliability or any of the other design

goals is the latest in the research agenda

(Asiedu and Gu 1998 Bralla 1996 Chu and

Holm 1994 Gupta et al 1997 Huang 1996

Huang and Mak 1998 Jansson et al 1990

Nevins and Whitney 1989 Priest 1990

Sanchez et al 1997 Ullman 1997)

While all these different design goals have

gained recognition and acceptance product

performance (or what is broadly known as

product functionality) as a design goal has

often been taken for granted by designers

Indeed the provision of functionality in a

product is the purpose of design It is possible

that even though product functionality may

have been an important initial product

design goal for designers the necessity to

accord other design goals (safety usability

quality etc) to a higher priority may have

relegated the task of ensuring functionality

in the prototype to a relatively lower priority

3 Function and functionality indesign definitions models andtools

Designs are considered to exist to satisfy some

purpose or function Thus knowledge of

functionality is essential in a wide variety of

design-related activities Such activities

include generation and modification of

designs comparison evaluation and selection

of designs and diagnosis or repair of designs

Beyond agreement among researchers and

designers that function is an important

concept in determining a productrsquos

fundamental characteristics there is no

clear uniform objective and widely

accepted definition of functionality Function

has been historically interpreted in a variety

of ways for instance as an abstraction of the

intended behavior of a design an indexing of

its intended behavior the relationship

between a design and its environment the

external behavior of a design or its internal

behavior (Umeda and Tomiyama 1997)

The definition of function has also been

influenced by design methodologies in use

For example if the designer follows the

traditional conceptual design methodology

the designer first determines the entire

function by analyzing the specifications of

the product to be designed and built He or

she then divides the function recursively into

sub-functions a process that produces a

functional structure For each sub-function

the next step is to use a catalog to look up the

most appropriate functional element plusmn a

component or a set of components that

perform a function Finally the designer

composes a design solution from the selected

elements Since the results of the design

process using the traditional conceptual

design methodology depend entirely on the

efficacy of the decomposition of the function

the role of functionality is critical in using

such a methodology (Pahl and Beitz 1988)

A number of new models for abstracting

and representing function in addition to

numerous computer-aided design tools for

managing the modeling of function in a

product have recently emerged For purposes

of discussion in this paper a model is a

conceptual or a theoretical model

represented in the form of diagrams and

other conventional representation methods

for concepts and ideas Any well-developed

[ 432]



device with a physical form that can be used

in real life to perform a design activity will be

classified as a tool plusmn for instance a software

to perform certain design activity will be

considered a tool whereas the algorithm that

is behind the functioning of a software will be

considered a model

31 Function and functionalrepresentation definitionsDictionaries define function as working

action and the action of something The

definition encompasses any of the specific

roles possessed by each mutually interacting

element constituting a whole

While functionality is considered an

intuitive concept dependent on the

designerrsquos intention traditionally there

have been three approaches in representing

function in design

1 representing function in the form of verb-

noun pairs (Miles 1961) plusmn an example

would be the function of a shaft to

` transmit torquersquorsquo

2 input-output flow transformations where

the inputs and outputs can be energy

materials or information (see Figure 2)

(Rodenaker 1971) and

3 transformation between input-output

situations and states plusmn the essential

difference between the definitions in 2 and

3 is the type of input and output plusmn for

example if the product is a household

buzzer according to definition 3 the

function ` to make a soundrsquorsquo can be

represented by two behavior states state 1

representing an upward clapper

movement and state 2 representing a

downward clapper movement (Goel and

Stroulia 1996 Hubka and Eder 1992)

Miles (1961) developed the function analysis

method of expressing a function as a verb and

direct object (a noun or an adjective) The

motivating idea for this definition is that any

useful product or service has a prime

function This function can usually be

described by a two-word definition such as

provide light (for a light source such as a

light bulb) pump water (for a domestic water

pump) and indicate time (for a clock) In

addition to primary functions there may be

secondary functions involved in a product

For example if the primary function of a

light source is to provide light a secondary

function could be that the light source may be

required to resist shock a pump for domestic

use with pumping water as the primary

function may have to operate at a low noise

level Although this definition of a function is

general due to the lack of clear description of

relationships between product function and

product structure this representation is not

considered powerful enough for design

applications Milesrsquo definition of function has

primarily been used in Value Engineering

(VE) work by representing a function in the

form of ` to do somethingrsquorsquo and by comparing

the value of function with respect to the costs

of the product

Rodenacker (1971) defined function as

transformation between input and output of

material energy and information (Figure 2)

An example using Rodenackerrsquos definition is

provided in Figure 3 In this example the

input can be conceptualized to consist of

coffee beans energy and information to the

system in the form of electrical signals (for

example control signals) the coffee mill is

the black box where the transformation of

coffee beans into ground coffee occurs the

output is ground coffee heat and

information to the user in the form of

electrical signals (such as electrical flash

light or electrical beep sound) Even though

this definition is widely accepted in design

research (Pahl and Beitz 1988 Welch and

Dixon 1992) it has limitations plusmn there are

functions that do not strictly involve

transformation between input and output

and Rodenackerrsquos definition of function does

not sufficiently describe such functions

Umeda et al (1990) proposed the FBS

(Function-Behavior-State) diagram to model a

system with its functional descriptions (see

Figure 4) Function according to Umeda et al

is a description of behavior abstracted by the

human through recognition of the behavior in

order to utilize the behavior The underlying

precept in the definition is that it is difficult to

distinguish function clearly from human

behavior and it is not meaningful to represent

function independently of the behavior from

which it is abstracted Function in the FBS

diagram is represented as an association of

two concepts the symbol of a function

represented in the form of ` to do somethingrsquorsquo

as Miles (1961) proposed and a set of

behaviors that can exhibit that function For

example some behaviors such as ` hitting a

bellrsquorsquo and ` oscillating a stringrsquorsquo may be used to

realize a function ` to make a soundrsquorsquo

Although the concept of symbolic information

is meaningful only to a human this

information associated with its behavior has

been found to be essential for supporting

design such as reuse of design results and

clarification of specifications It is easy to see

that function and behavior have a subjective

and many-to-many correspondence in their

relationship whereas the representation of

behavior of an entity can be determined more

objectively based on physical principles The

FBS diagram is intended to assist the designer

[ 433 ]



in the synthetic as well as analytic aspects of

conceptual design

According to Sturges et al (1990 1996)

function is defined as the domain-

independent characteristics or behavior of

elements or groups of elements Function

logic methods (see Figure 5) are modified by

Sturges et al for the development and use of

function block diagrams The idea behind

this definition of function is that the designer

should be able to describe the intended

function expand it into required

sub-functions and map the sub-functions

into components capable of fulfilling them

The design is assisted by the computer in this

process in terms of systematic identification

of functions allocation of constraints to

each function the interrelations between

functions and the evaluation of the

functions The approach supports the

designer mainly in the identification

articulation and evaluation of function

structures rather than the search for design

solutions and therefore applies to later

stages of task clarification and the early

stages of conceptual design

Figure 2Functional hierarchy in the traditional design methodology

Figure 3The function of a coffee mill as a black box

[ 434]



According to Welch and Dixon (1992 1994)

function is a set of causal relationships

between physical parameters as described by

the outward physical action of a device

Behavior is the detailed description of the

internal physical action of a device based on

established physical principles and

phenomena Functional design is the

transition between the three states (function

behavior and embodiment) shown in Figure

6 A design problem is stated in terms of a set

of functions that must be met for instance

the conversion of force to displacement The

functional information is transformed by the

phenomenological design process to behavior

information based on physical principles and

phenomena If the function is conversion of

force to displacement the physical principles

of Hookersquos law would be used to accomplish

the function The embodiment design process

using behavior graphs models the required

behavior as a guide to select and configure

systems of embodiments An embodiment is

an abstraction of a physical artifact such as a

spring gear-pair or electrical motor which

contains not only behavior information but

also constraint and evaluation information

In the case of conversion of force to

displacement a spring (or more specifically a

rectangular wire helical spring) could be

used to accomplish the function

Our review of the literature shows that the

use of the computer as a design tool

(Bracewell and Sharpe 1996 Chakrabarti

and Bligh 1994 Chakrabarti and Bligh 1996

Chakrabarti and Blessing 1996 Qian and

Gero 1996) has not changed the primary

definition of function though creating new

problems in transforming the design

information (which is usually abstract and is

a mixture of numeric text graphical and

empirical information) and evaluating

alternative design solutions (Peien and

Mingjun 1993 Peien et al 1996)

Figure 4Relationships among function behavior and state

[ 435 ]



As this review shows there is a multiplicity

of views and definitions about function in the

literature plusmn a unified view of function and

functionality is lacking

32 Function representation modelsFunctional modeling refers to a wide variety

of approaches to model a design and its

requirement from its functional aspects so as

to allow reasoning about its functionality for

various activities Two important functional

models warrant mention

Umeda et al (1990) propose the FBS

(Function-Behavior-State) diagram as a

framework to model a system with its

functional descriptions (see Figure 4) Since a

function in a system cannot be completely

described objectively the FBS model is

divided into a subjective and an objective

portion the transformation of an intended

function into its corresponding behavior is a

subjective process whereas the

transformation of the behavior into a

physical entity or a structure based on

known physical phenomena and laws is an

objective task

Goel and Stroulia (1996) propose a specific

type of functional model called Structure-

Behavior-Function (SBF) model The

essential difference between the SBF model

and the FBS model is that the ` Brsquorsquo in the FBS

model stands for output behaviors (eg

oscillating the clapper in a buzzer to make a

sound) while the ` Brsquorsquo in the SBF model

stands for internal behaviors (eg flow of

electricity and generation and destruction of

a magnetic field in a buzzer) Thus while

FBS models emphasize the representation of

the output behaviors of a device of which the

device functions are a subset SBF models

emphasize the representation of the internal

causal processes of the device that result in

the output behaviors of the device including

its functions Since internal behavior

Figure 5The general form of a function logic diagram

[ 436]



representation of devices enable device

diagnosis (for adaptive design and redesign

of physical devices) the SBF model results in

more information for functional

representation than a FBS model A number

of other researchers have used the SBF model

structure for functional representation

(Sembugamoorthy and Chandrasekaran

1986) and for adaptive design (Navinchandra

et al 1991)

33 Functional reasoning andrepresentation toolsFunctional reasoning is a design approach

that supports design in the conceptual stage

The main activities supported by functional

reasoning include function description

establishment of function structures and

generation and evaluation of concept

alternatives The advent of computers and

the development of artificial intelligence (AI)

techniques have provided a renewed focus on

reasoning about functions and extended the

area into diagnosis and explanation Several

of the functional models incorporating

different function definitions mentioned in

the previous section have been developed

further into tools that designers can use for

functional representation Some of the

commonly used traditional tools and the

more recent computer-based functional

reasoning tools are reviewed further in the

following sub-sections

331 Milesrsquos value engineering techniqueMiles (1961) proposed Value Engineering

(VE) as a technique to improve values of

products or services by changing their

material design system etc The technique

is aimed at maximizing product function

while minimizing cost VE techniques are

summarized in terms of VE job plans (see

Figure 7)

In value engineering product function is

represented as ` to do somethingrsquorsquo and

product value is represented by product cost

VE is performed by comparing the value of

function with respect to the costs of the

product The functions of products and

services are analyzed and their value

systematically improved through VE job

plans (Miles 1961) The basic steps in a VE

job plan are function definition function

evaluation and alternative plan preparation

The detailed steps in defining a function

include collection of data related to a VE

object plusmn a VE object is any system with a

function to perform The VE object is subject

to further function analysis Function

analysis helps generate function definitions

and weeding out unnecessary functions

Function evaluation involves cost analysis

by function and selection of object field

These are in the analysis phase of VE job

plan The steps in alternative plan

preparation (or synthesis phase) are idea

generation summary evaluation

concretization detailed evaluation and a

new proposal to improve product value

Value engineering is limited in its use for

product design and manufacturing purposes

in terms of its ability to generate product

structure from a given function plusmn it is only

concerned with evaluation of functions and

assumes the existence of sound relationships

between behavior and structure and

relationships between function and

structure

332 Function analysis system technique FAST)Function Analysis System Techniques or

Function Analysis an offshoot of the value

engineering technique are methods for

systematizing functions (Bytheway 1971)

Function analysis is an improvement over

value engineering in that it systematizes

defined multiple functions and helps identify

a basic function among multiple functions

The essential idea in function analysis is to

apply several questions to individual

functions in order to isolate the basic function

from among other functions For example

Figure 6Classification of design information and process

[ 437 ]



some of the questions for isolating higher-

order functions could be (Akiyama 1991)

What do you really want to do in

performing this function

What high-order function is the reason for


What is the function reason for having to

perform this function

These questions not only identify basic

functions but they clarify conceptual

relationships among individual functions

The function analysis technique can be

summarized as follows (Akiyama 1991)

1 Definition of component functions plusmn

Definition of the function of each

constituent component (part or

component) of the object of analysis

2 Determination of higher functions plusmn

Determination of higher functions

through the application of high-order

function questions to each of the defined

functions to form function groups

3 Formation of families for each functional

group plusmn Application of the protocol for

determining the basic function to each

function group to make function families

4 Determination of the highest function plusmn

Making a function group of the high-order

functions in existing function groups

then finding the highest function by

applying the protocol for determining the

basic function

5 Determining critical path plusmn Determining

the critical path function series by asking

the critical path questions

6 Completion of FAST diagram plusmn

Completion of the FAST diagram by

relating the other function families to the

critical function series

333 Rodenackerrsquos methodology forfunctional representationRodenacker (1971) proposed a functional

representation methodology for novice

designers This design methodology is based

on his definition of a function as discussed in

section 31 The process begins with a

designer initially determining the function of

a mechanical entity from specifications

provided The next step is to divide the

function into sub-functions sub-functions

into sub-sub-functions and so on until the

level where physical behaviors perform such

sub-functions As a result the functional

structure (main and the sub-functions) of the

product is clarified The designer then looks

up catalogs of mechanical elements for each

divided sub-function and chooses the most

appropriate element Finally the designer

constructs the machine from those selected

elements in the reverse process of dividing

the function This means that the function

structure is copied to the physical structure

of the machine in the embodiment design

process Here function plays a crucial role

because the results of the design entirely

depend on the division of the function

Researchers (Umeda et al 1990) point to

several drawbacks in Rodenackerrsquos

approach First the word ` functionrsquorsquo has no

clear definition Rodenacker uses it in

different degrees of abstraction ie

relationships between input and output of

material energy and information to

relationships between surface of mechanical

parts Second as explained in section 31 the

definition does not sufficiently describe a

function which is not transformation

between input and output eg the function of

a bolt and a nut which is to join parts Third

Figure 7Value engineering job plan

[ 438]



the mechanism for transforming a function

into sub-functions is unclear and can be

subjective There is no objective method nor

an algorithm to do so Fourth sub-functions

produced with Rodenackerrsquos methodology

imply a structure of the whole that is the sum

of the sub-structure correspondent to sub-

functions which is not the case in many

product domains

334 Bond graph approachRosenberg and Karnopp (1975) proposed an

approach to functional representation using

bond graphs (see Figure 8) for analyzing

dynamic systems The Bond Graph technique

is used to represent a system as a

composition of components such as

transformers sources and gyrators Each

component deals with power flow and has

effort parameters (such as pressure voltage

and force) and flow parameters (flow rate

current and velocity for example) at its

ports Components connect at their ports and

are categorized by the number of ports For

example a transformer is considered to be a

two-port component (Umeda et al 1990) It

also lets users graphically manipulate graphs

and easily construct differential equations

for further analysis (Finger and Rinderle

1989) Rosenberg and Karnoppsrsquos approach

uses a bond graph to represent power flow of

a dynamic system and reasons about system

behavior The approach is limited though in

that it deals with the structure of a system

and reasons about its behaviors but does not

deal with its functions (Umeda et al 1990)

This approach has two main drawbacks

1 Since only system power flows are

represented in this approach one cannot

represent the function of for example a

bolt and a nut using the bond graph

2 Since the represented behavior of a

system should be related to its

functionality the bond graph of the

system should be constructed by

considering its whole function ie

selection of parameter to use in the bond

graph and the level of description should

be determined manually (Umeda et al

1990 Finger and Rinderle 1989)

335 Adaptive design toolsBhatta et al (1994) and Goel and Stroulia

(1996) use the Structure-Behavior-Function

model (SBF) for function representation to

develop a design support tool called Kritik

This tool has a design-case memory that

represents each case as an SBF model After a

designer specifies a desired function Kritik

retrieves a case that is functionally similar to

a specified function and makes a

modification plan of the case The designer

first retrieves past designs with behavioral

specifications similar to the specifications of

the behaviors of the desired device The

designer then modifies the structure of a past

design to propose a candidate design for

achieving the desired behaviors Verification

of the candidate design and redesign if the

candidate design fails to provide the required

function are the next steps in the process

This process is continued until a design is

generated that delivers the desired behavior

An extended version of Kritik called IDEAL

(Integrated Design by Analogy and

Learning) supports analogical design by

using both case- and model-based reasoning

Even though IDEAL is useful during the

synthetic phases of design it is limited in

terms of scalability and practicality (Umeda

and Tomiyama 1997)

336 SchemebuilderBracewell and Sharpe (1996) propose a design

platform called Schemebuilder This tool is

aimed at seamless support of functional

design to detailed design based on the bond

graph formalism discussed in section 334

Schemebuilder uses the bond graph

technique to represent a function The

initial step in Schemebuilder is the creation

of a generalized function-means tree which

is a hierarchical decomposition of the

embodiment process for the required

functions A means is at least one

component and if necessary one or more

associated required functions which

possess certain required attributes

Figure 8Simple system with corresponding bond graph

[ 439 ]



(Bracewell and Sharpe 1996) Even though

Schemebuilder is a working tool that

supports both synthetic and analytical

design phases it carries with it the

disadvantages of the bond graph technique plusmn

it cannot effectively deal with functions not

represented as power flow

337 Sturgesrsquos extended function logicSturges et al (1996) use function logic and

Function Block Diagrams (FBD) (Figure 5) to

represent function A compact description of

function called the basic function of the

design is generated first It is then further

decomposed by design teams into secondary

functions all necessary to perform the main

function The decomposition process results

in a reasoning structure relating each

component to the basic function of the design

(Fowlkes et al 1972)

An example for using function logic and

function block diagrams is illustrated in

Figure 9 The basic function of an overhead

transparency projector is identified as ` to

enlarge and project imagersquorsquo The basic

function is achieved by directing the light

focussing the light and illuminating the

transparency all secondary functions Each

of these secondary functions can be further

decomposed to lower level functions as

shown

The computer-based tool incorporating the

FBD generator for developing functional

models provides help to the designer in

function-related activities at the conceptual

stage This tool is currently being improved

to incorporate methods for providing

automatic assistance in the function

allocation process with the realization that

function allocation process is highly

subjective and depends on judgement of more

than one person (design team member)

338 Umedarsquos function-behavior-statemodelerUmeda et al (1996) provide a conceptual

design support tool called the FBS modeler

based on their Function-Behavior-State (FBS)

modeling concept The FBS modeler has

knowledge bases for function prototypes

physical features and physical phenomena

With these knowledge bases the FBS

modeler supports conceptual design as

follows

Figure 9Preliminary function block diagram of an overhead projector

[ 440]



1 The designer selects required functions

from the function prototypersquos knowledge

base

2 Aided by decomposition knowledge of

function prototypes a designer

decomposes the required function and

sub-functions

3 The designer chooses physical features

that can embody each sub-function After

choosing physical features the designer

might discover that some features cannot

occur In such a case a sub-system

Qualitative Process Abduction System

(QPAS) reasons out candidates for the

missing physical features to satisfy the

physical conditions

4 Next the designer connects the

instantiated physical features to complete

the functional hierarchy This process

constructs the behavioral-level network

structure

5 Then a qualitative reasoning sub-system

simulates behavior As a result of the

simulation the system might discover

inconsistencies between the FBS model

constructed by the designer and the result

obtained The system will then indicate

phenomena that will not occur even

though the designer specifies it in the

initial FBS module

The main deficiency of the FBS modeler is

that it does not explicitly deal with the

geometry and kinematics of the product

which are essential concepts in mechanical

design

339 Quality function deployment QFD)The QFD concept was first introduced by Yoji

Akao in Japan in 1966 and brought to the

United States in 1984 The first book on QFD

was published in Japan by Mizuno and Akao

in 1978 (Mizuno and Akao 1994)

QFD stands for quality function

deployment which is one of the seven new

management tools in quality control QFD

serves as a visual language providing a

valuable link for translating customer

requirements into necessary system design

elements The main focus of QFD is

satisfying the consumer QFD starts the

problem by defining exactly what the

customer is looking for not the

organizationsrsquo assumption of what the

consumer wants By defining the product at

the beginning of the process and then

determining how this product definition

can be met most effectively by the

manufacturerprovider ensures proper

product design This enables the

manufacturerprovider to concentrate on

organizing management plans that improve

or provide the characteristics and functions

that most effectively meet customersrsquo

needs

Originally applied to manufacturing

facilities the QFD has now been adapted to

any environment in which the demands of a

customer need to be translated into the

technical aspects of design (Bossert 1991

Mears 1995)

4 Recommendations for futurework

The following conclusions emerge from the

review of the published literature

1 The majority of functionality literature

deals with mechanical systems design

Mechanical systems such as gears and

shafts form only a small portion of

consumer products since consumer

products have different functional

requirements than internal mechanical

components (for example a user interfaces

directly with a consumer product but only

indirectly with a mechanical component

inside a product) the traditional definitions

of functionality and the methods and tools

used in representing function need

considerable extension The definition

needs to include the notion of function and

functionality in consumer product design

Issues such as usability (of the function)

how safely the function is being provided

how efficiently and quickly the function can

be accomplished are necessitated due to the

user involvement in consumer product

design and need due consideration at the

function definition and representation

stages of product design

2 The task domains where functional

representations and models are

potentially applicable and useful are on

the rise The literature however shows

that very few design support systems have

been tested on real design cases or use

real designers in industrial environments

this issue needs serious consideration

Design support tools such as design

checklists generated by using actual

designer input and actual cases merit

attention

3 Most published works address generating

concepts to satisfy a required function

There is relatively little work supporting

the clarification of functionality

Evaluation alternative formulations of

the required functionality as well as

alternative design solutions has also

been by and large a neglected area that

needs substantial research input before an

overall functional reasoning support

system could be developed Again the

[ 441 ]



alternative design solutions have to be

generated from design support tools that

are developed with the help of actual

designer input and actual cases

4 Researchers thus far have mainly

focussed on providing function not on

ensuring that function in a product Part of

the reason for this may be the varied design

goals that keep emerging from time to time

For instance the quality movement of the

early 1990s highlighted quality as a major

design goal customers demanded quality

products and designers had to focus on

providing a quality product plusmn providing a

function in a product may have been taken

for granted by designers There are

manufacturing considerations in making a

product that may have a direct impact on

function definition functional

representation and the selection of a

physical entity that best represents a

certain function plusmn this linkage between

providing a function at the design stage

(through a physical entity) and ensuring

the function through proper selection of

manufacturing variables to ensure

functionality is completely lacking in the

published literature Section 5 of this paper

presents an example of a can opener

showing potential linkages between

functionality criteria and various

manufacturing variables (the design

variables are not considered in this paper

to contain the scope which otherwise

would become too large) Providing

function and ensuring it are perhaps the

most important steps in the product

development cycle As stated earlier

products with a problem in providing the

main function will never sell no matter

how sophisticated their details

5 Product functionality anexample of can opener

51 Design and manufacturing variablesEnsuring product functionality is possible

only by controlling the design and

manufacturing variables and keeping them

within an optimal range If a relationship

between functionality and design attributes

and a relationship between the design of a

product and its manufacturing attributes can

be developed it should be possible to enhance

and ensure a productrsquos overall functionality

Some possible design variables that may

affect product function include designer

experience (novice designer versus

experienced designer) design tools used (the

software and hardware used in design) the

type of design (creative versus adaptive

redesign) design budget and communication

mechanisms for parties involved in the

design (for example over-the-wall approach

versus concurrent engineering)

Manufacturing variables include both

material variables and manufacturing

process variables In selecting a material for

a product or a component the primary

concern of engineers is to match the material

properties to the functional requirements of

the component One must know what

properties to consider how these are

determined and what restrictions or

limitations should be placed on the

application Some material-related variables

that can affect product function significantly

include the type of material material

toughness hardness fatigue resistance etc

The type of material used for a component in

turn determines the manufacturing process

to use and all manufacturing process

dimensions such as machinability

formability weldability and assemblability

to mention a few Depending upon the

specific manufacturing process (for example

metal cutting casting joining surface

preparation heat treatmentsurface

hardening and coating used) in making a

component one or more process variables

need to be controlled for component and

product functionality to be optimal These

variables may include the cutting speed and

feed the depth of cut the temperature

presence or absence of lubricants duration of

machining the rate of coolingheating

current density and voltage and the type and

amount of solventquenchant used among

other variables (some variables are outlined

in Figure 10)

In addition to the design and

manufacturing variables the definition of

product function in itself needs

considerable extensions The view that

product function means product

performance is limited and narrow A

product not only has to perform the intended

function but must do so safely reliably

(every time the product is used) consistently

(for the life of the product) among other

factors and be user-friendly so as to enable

the user to perform the function quickly

efficiently and simply Thus because the

physical entity to use for performing a

certain function is dependent upon the

definition of the function and because we

propose an extension of the definition of

function to include more elements selection

of physical entities (from a catalog of existing

physical entities) and development of new

ones merits further attention Designer aids

that assist in choosing appropriate physical

entities to satisfy extended definitions of

[ 442]



consumer product function also need to be

developed

52 Can opener functionality-manufacturing linkagesThe can opener has five main parts upper

handle lower handle blade crank and the

drive sprocket The upper handle is joined

with the crank and drive sprocket to form a

sub-assembly The lower handle is joined to

the blade to form the second sub-assembly

These two sub-assemblies are joined to form

the overall assembly The upper and lower

handles are used for holding the opener and

for providing the gripping force When

mounted properly on to the can and gripped

with adequate pressure the cutting edge

pierces the can and the sprocket wheel holds

on to the top outside rim of the can The

crank wheel is used to apply a torque that

helps the blade cut the can lid and rotate the

can until the lid is completely severed

The main manufacturing operations

involved in the can opener are blanking

piercing bending heat treatment nickel

plating riveting swaging and tumbling

Functionality-manufacturing linkages

were obtained by using function

transformation matrices (FTM) similar to

quality function deployment (QFD) matrices

and tables

Function transformation matrices are used

as a tool for a structured approach for

defining functional requirements and

translating them into specific steps in order

to develop the needed products It allows

functional requirements to be taken into

consideration throughout all processes

beginning with the concept design activities

and continuing throughout the production

operations on the factory floor

Transformation matrices use a series of

relationship matrices to document and

analyze the relationships between various

factors While the details of the matrices vary

from stage-to-stage the basics are the same

In the conceptual design stage functional

requirements are identified and translated

into design and technical requirements

Product deployment is the second stage of the

transformation process Its purpose is to

translate the previously developed design

and technical requirements into product

specifications and features During the

process deployment stage various product

features are converted into the specific

manufacturing operations During the

manufacturing deployment stage various

Figure 10Potential design and manufacturing process variables

Figure 11Functional requirements plusmn design and technical requirementstransformation for can opener

[ 443 ]



manufacturing processes are related to

specific process and material variables that

control them Through such a stepwise

transformation of product functional

requirements into process and material

variables it is possible to ensure and control

the functionality of a product

Design and technical requirementsdeploymentThe functional requirements are listed in the

horizontal portion of the first stage of the

FTM process (Figure 11) The functional

requirements are based on our extended

function definition Here we just

demonstrate the whole processes plusmn the

detailed information about the criteria of

each definition is not included The

functional requirements are then translated

into the language a company can use to

describe its product for design processing

and manufacture The objective of this step is

to develop a list of design and technical

requirements that should be worked on to

achieve the functional requirements

Next the relationships between the design

and technical requirements and the

functional requirements are established in

order to identify the relative importance of

various design requirements Every

functional requirement in the horizontal

portion is compared with each design

requirement in the vertical portion The

degree of relationship is marked at the

intersection plusmn a black circle represents a

strong relationship a half black circle a

moderate relationship and a blank circle a

weak relationship

Product deploymentProduct deployment is the second stage of the

transformation process The design and

technical requirements taken from the

vertical column of the previous stage were

listed in rows at this stage (Figure 12) Based

on the previous design experience the product

features that were needed to satisfy these

design and technical requirements were

identified and listed in the vertical column

Figure 12Design and technical requirements plusmn product features transformation for can opener

[ 444]



The relationships between product feature

requirements were identified as before

Process deploymentProcess planning is the third stage of the

transformation process (Figure 13) Its

purpose is to determine the manufacturing

processes that will actually produce the

product by relating various product features

to the specific manufacturing operations

The critical product features requirements

identified in the previous stage are listed in

the horizontal portion of the matrix The

major process elements necessary to develop

the product were extracted from the process

flow diagram and are shown at the top of the

column section of the matrix

Manufacturing deploymentManufacturing planning is the culmination

of the work done in the three previous stages

In this stage the various manufacturing

techniques necessary to make the product

are related to process attributes that affect

them (Figure 14) For example the hardness

of the blade is affected by the rate of cooling

during the heat treatment process The rate

of cooling in turn is controlled by the

properties of the quenching liquid

Producing of burrs is another example These

are sharp edges along the shearing lines of

the cut parts Production of burrs depends on

the excessive die-punch clearance during

blanking and the dull cutting edges of the die

The die-punch clearance should be properly

designed and worn die edges should be

eliminated Even though the manufacturing

process adopted for producing the can opener

is affected by numerous process variables

only those variables that affect the can

openerrsquos functionality are considered here

The manufacturing techniques are listed in

the horizontal portion and the process

variables are listed in the vertical portion of

the FTM (Govindaraju 1999)

Through a FTM analysis a clear

progression of the relationships linking

product functionality features and

manufacturing variables is established The

FTM shows that the overall functionality of a

Figure 13Product features plusmn process transformation for can opener

[ 445 ]



product can be enhanced by adopting the

optimum range of values for the process

variables Thus to ensure functionality those

manufacturing variables that affect

functionality features must be tightly

controlled

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Systematic Improvement of Quality and

Performance Productivity Press Inc

Cambridge MA

AsieduY and Gu P (1998) ` Product life cycle

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International Journal of Production Research

Vol 36 No 4 pp 883-908

Bakerjian R (1992) ` Design for

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Engineering Handbook Vol 6 Society of

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Bhatta S Goel A and Prabhakar S (1994)

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Billatos SB and Nevrekar VV (1994)

` Challenges and practical solutions to design

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Design for Manufacturability ASME New

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Boothroyd G (1994) ` Product design for

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Boothroyd G and Dewhurst P (1983) Design for

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MA

Bossert JL (1991) Quality Function Deployment

plusmn A Practitionerrsquos Approach ASQC Quality

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Bracewell RH and Sharpe JEE (1996)

` Functional descriptions used in computer

support for qualitative scheme generation plusmn

schemebuilderrsquorsquo AIEDAM Vol 10 No 4

pp 333-46

Bralla JG (1996) Design for Excellence McGraw-

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Brauer RL (1990) Safety and Health for

Engineers Van Nostrand Reinhold New

York NY

Bytheway CW (1971)` The creative aspects of

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Eng Conf pp 301-12

Chakrabarti A and Blessing L (1996) ` Special

issue representing functionality in designrsquorsquo

Artificial Intelligence for Engineering Design

Analysis and Manufacturing (AIEDAM)

Vol 10 No 4 pp 251-370

Figure 14Process features plusmn process variables transformation for can opener

[ 446]



Chakrabarti A and Bligh TP (1994) ` An

approach to functional synthesis of solutions

in mechanical conceptual design part I

introduction and knowledge representationrsquorsquo

Research in Engineering Design Vol 6

pp 127-41


approach to functional synthesis of

mechanical design concepts theory

applications and emerging research issuesrsquorsquo



Vol 10 No 4 pp 313-31

Chu X and Holm H (1994) ` Product

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No 1 pp 29-38

Cross N (1989) Engineering Design Methods

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Finger S and Rinderle JR (1989) ` A

transformational approach to mechanical

design using a bond graph grammarrsquorsquo Design

Theory and Methodology plusmn DTM rsquo89 pp 107-16

Fowlkes JK Ruggles WF and Groothuis JD

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Manufacturability Producibility Handbook

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Goel A and Stroulia E (1996) ` Functional

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Gupta SK and Nau DS (1995) ` Systematic

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Hermann F (1994) ` Environment considerations

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Huang GQ (1996) Design for X- Concurrent

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Huang GQ and Mak KL (1998) ` Re-

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No B4 pp 259-68

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Hundal MS (1994) ` DFE Current status and

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Jansson DG Shankar SR and Polisetty FSK

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Design Theory and Methodology plusmn DTM rsquo90

pp 85-96

Kusiak A and He DW (1997) ` Design for agile

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Lacey R (1986) Ford The Man and the Machine

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Miles LD (1961) Techniques of Value Analysis

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Mital A and Anand S (1992) ` Concurrent

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Miyakawa S Ohashi T and Iwata M (1990)

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Navinchandra D Sycara K and Narasimhan S

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Peien F and Mingjun Z (1993) ` The research on

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designrsquorsquo Proc 3rd Nat Conf Eng Design

Industrial Press Beijing China pp 101-4

Peien F Guorong X and Mingjun Z (1996)

` Feature modeling based on design

catalogues for principle conceptual designrsquorsquo


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Analysis and Manufacturing Vol 10 No 4

pp 347-54

Priest JW (1990) ` State of the art review of

measurement procedures in product design

for manufacturingrsquorsquo Manufacturing

Proceedings of Manufacturing International

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Qian L and Gero JS (1996) ` Function-behavior-

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based designrsquorsquo Artificial Intelligence for



Rodenacker W (1971) Methodisches

Konstruieren Springer Berlin Heidelberg

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Roozenburg NFM and Eekels J (1995) Product

Design Fundamentals and Methods John

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Introduction to Physical System Dynamics

McGraw-Hill New York NY

Runciman C and Swift K (1985) Assembly

Automation Vol 5 No 3 pp 17-50

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` Intelligent reasoning assistant for

incorporating manufacturability issues into

the design processrsquorsquo Expert Systems with

Applications Vol 12 No 1 pp 81-8

Sembugamoorthy V and Chandrasekaran B

(1986) ` Functional representation of devices

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Riesbeck CK (Eds) Experience Memory and

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pp 255-74

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Transactions (Institute of Industrial

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Umeda Y and Tomiyama T (1997) ` Functional

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Umeda Y Ishll M Yoshioka M Shimomura Y

and Tomiyama T (1996) ` Supporting

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behavior-state modelerrsquorsquo Artificial

Intelligence for Engineering Design Analysis

and Manufacturing Vol 10 No 4 pp 275-88

Umeda Y Taketa H Tomiyama T and

Yoshikawa H (1990) ` Function behavior

and structurersquorsquo in Gero JS (Ed) Application

of Artificial Intelligence in Engineering V

(Design) Proceedings of the Fifth

International Conference Vol 1 Boston MA

Van Hemel CG and Keldmann K (1996)

` Applying DFX experience in design for

environmentrsquorsquo in Huang GQ (Eds) Design

for X- Concurrent Engineering Imperatives

Chapman amp Hall New York NY

Wall Street Journal (1999) April 26 and 27

Welch RV and Dixon JR (1992) ` Representing

function behavior and structure during

conceptual designrsquorsquo Design Theory and

Methodology DE-Vol 42 ASME New York

NY

Welch RV and Dixon JR (1994) ` Guiding

conceptual design through behavior

reasoningrsquorsquo Research in Engineering Design

Vol 6 pp 169-88

Ziemke MC and Spann MS (1993) ` Concurrent

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Concurrent Engineering Contemporary Issues

and Modern Design Tools Chapman and Hall

New York NY pp 24-41

[ 448]



functionality with examples for each

definition A review of the different models to

represent function and the existing tools to

provide functionality follows It should be

noted that the preponderance of published

literature in the functionality and functional

representation areas is on mechanical

systems design relatively very few articles

are in the manufacturing engineering

domain Also research on mechanical design

in specific technical domains such as

mechanisms and heat exchangers is beyond

the scope of this paper Section 4 provides

recommendations for further research

Section 5 presents an example to show how to

ensure product functionality and illustrates

potential linkages between functionality

criteria and manufacturing variables for a

can opener

2 Design goals history andevolution

Historically a variety of factors both

internal and external to a company have

influenced its product design goals For

Figure 1Various types of can openers

[ 431 ]


























































































































[ 432]









considered a model










function in design

















































of the product























































[ 433 ]




conceptual design



























[ 434]
















































[ 435 ]


























objective task




















[ 436]












et al 1991)




























Figure 7)



































structure














[ 437 ]


































basic function















































[ 438]











product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]


























































































































[ 432]









considered a model










function in design

















































of the product























































[ 433 ]




conceptual design



























[ 434]
















































[ 435 ]


























objective task




















[ 436]












et al 1991)




























Figure 7)



































structure














[ 437 ]


































basic function















































[ 438]











product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]









considered a model










function in design

















































of the product























































[ 433 ]




conceptual design



























[ 434]
















































[ 435 ]


























objective task




















[ 436]












et al 1991)




























Figure 7)



































structure














[ 437 ]


































basic function















































[ 438]











product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]




conceptual design



























[ 434]
















































[ 435 ]


























objective task




















[ 436]












et al 1991)




























Figure 7)



































structure














[ 437 ]


































basic function















































[ 438]











product domains




































































and Tomiyama 1997)

















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base




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structure









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Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























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and tables






























[ 443 ]





































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[ 444]


















































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controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]
















































[ 435 ]


























objective task




















[ 436]












et al 1991)




























Figure 7)



































structure














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product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




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physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























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pp 255-74


































NY




Vol 6 pp 169-88






[ 448]


























objective task




















[ 436]












et al 1991)




























Figure 7)



































structure














[ 437 ]


































basic function















































[ 438]











product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























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pp 255-74


































NY




Vol 6 pp 169-88






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et al 1991)




























Figure 7)



































structure














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and Tomiyama 1997)

















[ 439 ]































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follows


[ 440]





base




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Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]


































basic function















































[ 438]











product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




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structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]











product domains




































































and Tomiyama 1997)

















[ 439 ]































shown




















follows


[ 440]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]































shown




















follows


[ 440]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]





base




sub-functions









physical conditions





structure









initial FBS module





design



























needs






Mears 1995)







































attention












[ 441 ]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]


































































































in Figure 10)
























[ 442]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]




developed


























and tables






























[ 443 ]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]





































weak relationship











[ 444]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]


















































[ 445 ]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]








controlled




Cambridge MA




Vol 36 No 4 pp 883-908














York NY pp 49-64






MA



Press Milwaukee WI





pp 333-46





York NY



Eng Conf pp 301-12





Vol 10 No 4 pp 251-370


[ 446]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]








pp 127-41







Vol 10 No 4 pp 313-31




No 1 pp 29-38
























MA




Vol 27 No 5 pp 323-42








Englewood Cliffs NJ





pp 35-48



New York NY






No B4 pp 259-68






York NY pp 89-98





pp 85-96










NY








Newport RI





pp 23-5




Organization Tokyo









York NY





York NY



Berlin









[ 447 ]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]




pp 347-54













New York



























Pittsburgh PA






pp 255-74


































NY




Vol 6 pp 169-88






[ 448]



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