Product Design for the Environment: A Life Cycle Approach - Chapter 11 potx

Chapter 11 Product Constructional System Defi nition Based on Optimal Life Cycle Strategies The design of products with good environmental performance over their entire life cycle re

Methods, Tools, and

Case Studies

Chapter 11

Product Constructional System Defi nition

Based on Optimal Life Cycle Strategies

The design of products with good environmental performance over their

entire life cycle requires the development of methods and models that provide

as complete a vision of the problem as possible, and allow the optimization

of product architecture and components while respecting the constraints

imposed by their main functional performances

This chapter presents a method for Life Cycle Design, focusing on the

analy-sis of strategies extending the useful life (maintenance, repair, upgrading, and

adaptation of the product) and strategies of recovery at the end-of-life (direct

reuse of components and recycling of materials) This analysis and design

method is able to evaluate the most suitable strategies for each component and

subassembly comprising the product, and to defi ne the best redesign choices

in terms of certain characteristics of product architecture and components It is

based on a process of analysis and decomposition of the conventional

construc-tional system and its reinterpretation in terms of the life cycle strategies, by

means of the modularity concept and the Design for Disassembly approach To

clarify this method, the development of a redesign proposal for a widely used

household appliance, the refrigerator, is described

The fundamental issues in this chapter were previously introduced in

11.1 Aims and Approach

This chapter presents a method, complete with fundamental mathematical

modeling, to aid the study of product constructional systems and investigate

their environmental effi ciency The latter can be determined in various ways

The approach proposed here seeks to optimize the life cycle strategies that

appear to be more effective for an environmentally effi cient life cycle

(Section 9.1, Chapter 9):

• Those strategies aimed at maintaining performance and functionality

of product during the phase of use (maintenance, repair, upgrading, Chapter 9

and adaptation of the product), in that they can favor the extension

of the product’s useful life

• Those strategies oriented toward the planning of recovery processes

at the end of the product’s useful life (direct reuse of components and recycling materials in the primary production cycle or in exter-nal cycles), in that they are directed at reducing the environmental impact of disposal and at the recovery of resources

These types of interventions can be translated into clear environmental

benefi ts: reduction of the volumes of the virgin materials required;

exten-sion of the product’s working life; closing the cycles of the resource fl ows in

play by recovery operations The proposed tool is conceived to support two

action typologies:

• Analysis of conventional constructional systems for a correct defi

-nition of the life cycle strategies most appropriate to preexisting products

• Redesign of architectures and components for the improvement of

environmental performance and for the development of new, ronmentally acceptable products

To translate the strategies of extension of useful life and recovery into

requi-sites of product architecture and components, we propose the modularity

(Chapter 9, Section 9.3.3), which focus on harmonizing product layout,

geom-etries, and joining systems in terms of the separability of the parts

11.2 Method and Tools for Analysis and Design

An analysis and design intervention characterized by the premises outlined

above is complex and requires a methodology that provides a procedure and

supporting tools for the defi nition and correct interpretation of

environmen-tal requirements Such a methodology must also identify the most effective

elements of successful product redesign

The method developed here is divided into certain successive moments,

tion of the conventional constructional system, which identifi es the deter-

mining characteristics of the product architecture, the unavoidable design

constraints, and the primary functional components Then follows an

evalu-ation of the most appropriate strategies of extension of useful life and of

product architecture (reinterpreted using the evaluation tool) is mapped to

concept (Chapter 9, Section 9.4) and the Design for Disassembly approach

summarized in Figure 11.1 The fi rst phase is the analysis and

decomposi-recovery, according to the system characteristics Finally, the conventional

evidence the distribution of the most appropriate strategic options in

rela-tion to the characteristic properties of the product’s various parts This offers

views of the system that can suggest the most effective design interventions

and recommend the structure of the architecture and modularization of the

system that best respect these options

At the component and junction design level, this last phase requires the

ing the separability of the new constructional system (allowing the disassembly

of the main components) and making it possible to apply the optimal strategies

A product that provides for relatively easy separation of its parts or

compo-nents can facilitate product maintenance, repair, and updating, and the

separa-tion of components and materials for recovery at the end of its useful life

This type of investigation can have dual goals: the defi nition of the most

suitable strategies to apply to predefi ned, conventional constructional systems,

and development of new architectures aligned with the most effective

strate-gies for extending useful life and recovery of resources

In general, “product architecture” refers to the arrangement and

relation-ships of the physical blocks comprising the functional elements of a product

FIGURE 11.1 Summary of analysis and design method.

Design for Disassembly approach (Chapter 9, Section 9.3.3), directed at

ensur-(Ulrich and Eppinger, 2000) “Functional elements” are those units that

perform single operations and transformations that contribute to the overall

product function Defi ning product architecture thus consists of defi ning its

approximate geometric confi guration (layout) and identifying the

interac-tions between its main units or modules A successive level of analysis refers

to the defi nition of component characteristics (dimensions, shape, material)

and of junction systems

Product constructional system is defi ned in two successive levels of design

choices:

• Modularity and layout (embodiment design)

• Properties of components (detail design)

These choices, in turn, determine two corresponding typologies of component

characteristics: separability and accessibility, and performance (durability,

reli-ability and other physical characteristics)

Among the different approaches to architecture decomposition,

decomposi-tion by modularity is considered more appropriate in this context because it

analyzes the independence of functional and physical components Unlike

structural decomposition, which is restricted to a hierarchical model of the

system, decomposition by modularity exploits the lack of dependency between

physical components of the design (Kusiak and Larson, 1995) This choice is

motivated by the strategic value that architecture modularity has in relation to

In the method proposed here, the analysis and decomposition of product

architecture consists of three phases:

• Defi nition of the main functional units

• Analysis of the interaction between units (and defi nition of the

consequent layout constraints)

• Analysis of the characteristic performances required of each unit

The functional units are those that collectively produce the overall functioning

of the system, divided into physical blocks that perform the single operations

Therefore, the defi nition of functional units requires an initial, function-based

decomposition (Kirschman and Fadel, 1998) First, the overall function is

deter-mined for the system Then, depending on its complexity, it is broken down

into subfunctions which, if necessary, may be decomposed again to produce

a functional graph that approximates the subsystem boundaries and

trans-lates the functional units into physical blocks

the design of product life cycle, fi rst described in Chapter 9, Section 9.4

The results of the analysis of the interactions between the units may be

expressed by a symmetrical interaction matrix:

Analyzing the characteristic performance of the functional units consists of

defi ning the performance constraints that, for each unit, can be expressed by

one or more functions of the type:

where Pf represents the characteristic performance, Gf and Gv are the fi xed

and variable geometric parameters, respectively, Sh represents the form

char-acteristics, and MtPp represents the properties of the material (Giudice et al.,

2005)

11.2.3 Investigation Typologies

As mentioned above, the method proposed here supports two different

investigation typologies:

• Analysis of conventional constructional systems for a correct defi

ni-tion of the most suitable intervenni-tions for preexisting products and

an evaluation of environmental criticality

• Product redesign for the improvement of environmental

perfor-mance in the life cycle

11.2.3.1 Analysis of Criticality and Potentiality of the

Conventional System

At this level of intervention, the proposed method is directed at the best

mapping of strategies for extending useful life and recovery at end-of-life,

according to the properties of the preexisting construction units This mapping

is achieved using the matrix of strategy evaluation described below The matrix

translates certain determinant factors for the single strategies into component

suitability to the strategy The determinant factors, as shown below, are

classi-fi ed as dependent on, or independent from, the design choices

In the case where a preexisting structure is analyzed, the design choices

have already been made and therefore the entire set of these factors must be

evaluated to defi ne the optimal strategies From the analysis of the

conven-tional construcconven-tional system it is possible to:

• Defi ne the main components and their constituent materials

• Identify the functional units

• Evaluate the modularization of the architecture by analyzing the

correspondence between functional units and components

• Analyze the interactions between the components (which must

respect the necessary interactions between functional units) This provides a matrix of component interaction:

IC icij

mxm

Using the matrix of strategy evaluation, it is possible to quantify the relevance

of each main component of the product in relation to each strategy of useful

life extension and end-of-life recovery Then, to ensure that the most suitable

strategies are actually feasible, the architecture must allow the necessary

sepa-rability of the components To evaluate sepasepa-rability, which represents the

main criticality of the architecture, the matrix defi ned by Equation (11.3) must

be transformed into a matrix of the irreversible junctions (each interaction is

translated into junction)

IC* ic*ij

mxm

where ic* ij is 1 if the junction between the i-th and j-th components is

irrevers-ible, and 0 if it is reversible or nonexistent, or if i ⫽ j The separability of the

components can then be expressed by the following vector:

m

(11.5)

The i-th component is separable if sci⫽ 1, otherwise it is inseparable (sci⫽ 0 ).”

11.2.3.2 Redesign of Product

From the viewpoint of Life Cycle Design, the modularization of the

constructional system must achieve two main objectives regarding life cycle

requirements: the independence of components belonging to different

modules, and the affi nity of components of the same module (Gershenson

et al., 1999) This assumption is the foundation of redesign intervention

The fi rst phase of system redesign is the analysis of opportunities for

archi-tecture redesign based on the functionality and performance constraints

imposed on the main units, introduced in Section 11.2.2 and expressed by the

interaction matrix (11.1) and by a function set of type (11.2) In architecture

redesign, the tool used for the evaluation of optimal strategies ignores the

determinant factors directly dependent on design choices (which must

subse-quently be optimized), and takes into account only those dependent on

factors external to the design choices (required characteristics and

function-ality, conditions of use)

The results of this fi rst analysis, dependent on solely external factors,

indi-cate which design choices would respect the predisposition of each

compo-nent to useful life extension and end-of-life strategies With these results it is

also possible to identify any affi nities that may exist between components

Components similar in terms of suitability for both the strategies and the

required functional performance can be appropriately grouped and

modu-larized, in order to facilitate, for each module identifi ed, the most appropriate

servicing or recovery operations (Marks et al., 1993) These indications are

then implemented in the fi rst level of design choices (layout, modularity)

that falls within the domain of the embodiment phase of the design process

modify the interaction matrices of the functional units (11.1) and of the

components (11.3)

The next level of design choices (that of components—typology of

materi-als, durability, reliability) that falls within the domain of the detail design is

approached in terms of:

• Required performance characteristics, expressed by (11.2)

• Indications obtained from the preliminary evaluation of the optimal

strategies The optimal choice is identifi ed by varying the design parameters and evalu-

ating the subsequent effects on the strategy distribution

To complete redesign, the degree of appropriate separability can be

identi-fi ed for each module, in order to ensure a reduced impact (generally economic)

of the disassembly phase Therefore, the system of junctions must be defi ned

so that it ensures:

• Functional interaction between components

• Separability, enabling the strategies identifi ed as optimal for each

component (Chapter 7) Having redefi ned the main components, it is necessary to

Also in this case, separability also depends on the system of junctions through

a matrix of type (11.4) and can be expressed using a vector as in (11.5) The

required separability becomes the objective of the Design for Disassembly

intervention, which guides the fi nal phase of redesign at the component and

11.2.4 Verifi cation Tools

The results of redesigning must be analyzed to evaluate their effectiveness in

extending the product’s useful life, these results can be evaluated using the

tools for the analysis of product serviceability, which quantify its level of

maintainability and reparability as a function of constructional system effi

-ronmental impact, it is possible to apply the tools of Life Cycle Assessment

(LCA), which allow the evaluation of the environmental impact of the

By evaluating the redesigned product in this way and comparing the

results with those obtained on the conventional system, it is possible to

determine the effectiveness and the success of the redesign, and its resulting

benefi ts

11.3 Optimal Life Cycle Strategy Evaluation Tool

The evaluation tool that enables useful life extension and recovery strategies

to be related to the product parts and subsystems consists of a set of matrices

that quantify the relevance of each main component in terms of each

practi-cable strategy This quantifi cation is obtained by evaluating the potentiality

of the components in relation to the determinant factors for each strategy

(Chapter 9, Sections 9.2.3 and 9.3.5)

The determinant factors are properties of components that render them

appropriate for the application of one or more of the life cycle strategies

under examination For example, a component that requires frequent

clean-ing and is particularly susceptible to deterioration is a good candidate for

regular maintenance; thus, the need for cleaning and the susceptibility to

terms of reaching the desired goals (Section 3.2.3, Chapter 3) With respect to

mized product’s life cycle (Chapter 4)

junction system levels (refer to Chapter 9, Part Design and Joint Design,

Section 9.3.3.1 and Table 9.2)

ciency (Chapter 9, Section 9.2.2,) To evaluate performance in terms of

envi-physical deterioration can be considered determinant factors for the

mainte-nance strategy

Determinant factors, as noted above, are distinguished by their

depen-dence on, or independepen-dence from, the design choices The former (durability,

reliability, resistance) are directly dependent on choices made at the

compo-nent level (materials, geometry) They are generally quantifi able by

evaluat-ing physical–mechanical properties and by applyevaluat-ing tools and techniques

latter type depend on factors external to design choices (required

character-istics and functionality, conditions of use) Generally, their quantifi cation

can only be based on qualitative evaluations

The determinant factors that will be considered here are summarized in

depending on design choices are displayed in italics

create a strategy analysis matrix, the main components must fi rst be entered

according to the indications obtained from the preliminary analysis and

decomposition of product architecture

Each component has a line of evaluation terms, one term for each

determi-nant factor for the strategy for which the potential of the components is to be

evaluated In this way a matrix can be developed for each strategy, completed

TABLE 11.1 Extension of useful life strategies and determinant factors

PHYSICAL DETERIORATION

DURATION

RELIABILITY DURATION

USE MODE CHANGES USE ENVIRONMENT CHANGES The determinant factors that depend on design choices are italicized.

for the analysis of component duration and life prediction (Chapter 10) The

Tables 11.1 and 11.2 in relation to each strategy under examination Those

Figure 11.2 shows the basic set of matrices for evaluation of strategies To

by a fi nal column consisting of global evaluation terms representing the

overall evaluation of each component These fi nal terms are the sum of the

terms in the corresponding matrix line, appropriately weighted according to

the importance of each determinant factor

For example, to evaluate a component’s potential in relation to maintenance

strategies, the corresponding matrix will consist of three columns, one for each

terms quantifying each component’s need of cleaning operations The second

column will consist of terms quantifying each component’s susceptibility to

FIGURE 11.2 Scheme of strategy evaluation matrices.

TABLE 11.2 End-of-life strategies and determinant factors

The determinant factors that depend on design choices are italicized.

determinant factor for maintenance (Table 11.1) The fi rst column will consist of

deterioration The third column will consists of terms quantifying each

component’s lifespan Further (conclusive) column will report the overall

evaluations

In a fi rst analysis, the terms of intermediate and overall evaluation could

be based on a qualitative evaluation of the determinant factors for each

strat-egy A quantitative evaluation approach may be formulated (Giudice et al.,

2002), based on the mathematical model summarized as follows

Have C i indicate the i-th of the m components comprising the product,

and have DF j X indicate the j-th of the n X determinant factors for the

practi-cable strategy X The matrix M X for the evaluation of strategy X can be

expressed as:

M = mx

ij x

i = 1,2, ,m

j = 1,2, ,n x

where the term m ij X quantifi es the j-th determinant factor for the strategy X,

relative to the i-th component

Then have w j X indicate the weight of the j-th determinant factor for strategy X

The aptness A i X of the i-th component C i to strategy X represents the Index of

Strategy X for the i-th component:

A ix w m

j x j=1

n

ij x

x

A correct use of the proposed model requires not only an appropriate

quan-tifi cation of the strategy determinant factors, but also their normalization to

render them homogeneous in relation to the application of (11.7), and an

evaluation of the weighting of each factor in relation to the strategy

11.4 Case Study: System Analysis and Redesign of a

Household Refrigerator

Large, domestic electrical appliances (refrigerators, washing machines,

dish-washers) generally have an average life estimated at about 10 years This

period represents the potential life of the product since it corresponds to a

prevision of usefulness (i.e., to the time it is anticipated the appliance can

This potential life can be signifi cantly reduced by the design cycle (i.e., the

interval of time between successive generations of the product), whereby the

production of a model is discontinued four to fi ve years after its fi rst

appear-ance on the market This characteristic of brief effective useful life, together

maintain its primary functions—physical life, see Section 9.1 of Chapter 9)

with their widespread use in all domestic environments, makes electrical

appliances particularly sensitive to problems of retirement and recovery

In the case of the refrigerator, this problem is amplifi ed by the large variety of

product typologies produced to meet varying consumer demands, which can

make it vulnerable to a further reduction in its useful life This is compounded

by a problem of recovery resulting from the conventional product

construc-tional system that, at present, combines a wide variety of different and

incom-patible materials inseparably (EC-VHK, 1999) The walls of refrigerators, in

particular, are composed of metals, plastics, and PUR foam glued together;

because they cannot be disassembled or dismantled, they are usually cut up,

shredded, or ground up (Lambert and Stoop, 2001)

These problems have led to legislative pressures and incentives intended to

limit the environmental impact of this specifi c manufacturing sector,

operat-ing on many phases of the life cycle In the European Union, for example, use

of refrigerating fl uids and foaming agents responsible for increased

deteriora-tion of the ozone layer and global warming (chlorofl uorocarbons—CFCs) has

been discouraged or suppressed The introduction of energy labels showing

products’ energy consumption has been complemented by certifi cation of

products’ overall eco-compatibility, within the EC’s eco-label award scheme

eco-label to refrigerators was issued in 1996; in its 1999 revision (2000/40/

EC), the previous criteria were integrated with explicit requirements

regard-ing the extension of useful life (lifetime extension) and the facilitation of

prod-uct disassembly for recovery and recycling at end-of-life That revised directive

required that joints must be easy to fi nd and be accessible, electronic

assem-blies and the whole product must be easy to dismantle, and incompatible and

hazardous materials must be separable These key criteria were confi rmed in

the last revision (2004/669/EC)

Following this methodology, the fi rst phase consists of a preliminary analysis

and decomposition of the constructional system to defi ne the main functional

units, the interactions between units (and consequent layout constraints), and

the characteristic performances required of each unit In the case of the

refrig-and associated with their main performance characteristics The matrix of the

Conventional Architecture

From the analysis of the conventional system it is possible to defi ne the main

components and their materials and to identify the functional units, as shown

(Chapter 1, Section 1.6.1) The fi rst EC directive on criteria for awarding the

erator, the six main functional units summarized in Table 11.3 were identifi ed

interactions between the main units (11.1) is reported in Table 11.4

ing action generated by the cooling plant 5 to the internal cell 4) coincides

with part of the plant itself (evaporation plate); thus, units U 5 and U 6 are

grouped together in a single component C 5 (cooling plant)

From the conventional architecture analysis it is also possible to determine

the main criticality—the impossibility of separating the parts at the end of the

working life because of the foam insulation element that joins all the cabinet

components and part of the cooling system This criticality is expressed by the

reported in the upper part and the consequent vector of component

separabil-ity (11.5) is given on the lower line

This analysis was directed at producing the most correct mapping of the

strategies of extension of useful life and recovery at end-of-life, in relation to

the properties of the components This mapping was achieved using the

strategy evaluation matrix described above (Section 11.3) Use of the matrix

quantifi es the relevance of each essential component of the product in

rela-tion to each feasible strategy

ing to the reuse strategy Using the matrix in an analogous manner, it is

TABLE 11.3 Functional units and main performances requested

insulation

TABLE 11.4 Functional interaction between main units

matrix reported in Table 11.5, where the irreversible junctions (11.4) are

in Figure 11.3 It can be seen that in this case, unit 6 (which transfers the

As an example, Figure 11.4 shows the application of the matrix