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CIRP Annals - Manufacturing Technology 61 (2012) 175–178

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LC-CAD: A CAD system for life cycle design

Yasushi Umeda (2)*, Shinichi Fukushige, Eisuke Kunii, Yuki Matsuyama

Graduate School of Engineering, Osaka University, Osaka, Japan

1. Introduction

A promising approach for sustainable development is theconstruction of the sustainable product life cycle systems thatdrastically reduce environmental loads, resource consumption,and waste generation while increasing living standards andcorporate profits. Product life cycle design plays a crucial role inthis progress [1–3]. In such design, designers should consider boththe product and its life cycle, as the life cycle is closely coupledwith product’s structure, geometry, and other attributes.

A number of studies have addressed environmentally consciousproduct design. Examples include design for recycling [4],remanufacturing/reuse [5], maintenance [6], and ease of disas-sembly [7]. However, as such design for the environment (DfE)methods focus only on certain aspects in the entire product lifecycle, the complexity and coupling of a diverse range of life cycleissues render such design approaches inadequate. For example, if adesigner attempts to create a product structure suitable formaintenance, the structure might make it difficult to disassemblethe product for recycling. In order to establish the sustainableproduct life cycle systems, resolving such conflicts and trade-offsamong numerous design aspects is required.

Although CAD systems for product design are quite popular, nocomputational support framework for designing both a productand its life cycle (i.e., life cycle design) has yet been established. Lifecycle design includes modeling the life cycle besides the product,and evaluating and optimizing both of them from variousviewpoints [8]. Some studies have addressed such modeling andevaluation schemes for product life cycles [9,10]. However, thesemethods mainly focus on the selection of optimal processes and

communication between specialized models and regulates tsystem-level behavior. PLM does not provide models that suppdesign activity of product life cycles.

The objective of this study is to propose a computer-aidesign system called LC-CAD (Life Cycle-CAD) for life cycle desTo this end, this paper proposes a scheme for representinproduct and its life cycle in an integrated manner and a methodmanaging consistency between the two. Based on this modeand management scheme, the system also allows designerevaluate environmental, economic, and other performance ofdesigned life cycle using LCS (life cycle simulation) [8,12].

The rest of the paper is organized as follows: Section 2 propothe integrated product life cycle model. Section 3 outlines

architecture of LC-CAD and its management and evaluasubsystems. Section 4 illustrates a case study with LC-CAD ocellular phone. After the discussion of the case study in SectioSection 6 concludes the paper.

2. Integrated product life cycle model

For constructing LC-CAD, we propose a computational mothat enables design, management, and evaluation of a product

its life cycle comprehensively. The model also represents chanof the product during its life cycle (e.g., a component is shredinto metal fragments in a recycling process) to enable

management and visualization of all product states in relato the processes of the life cycle. Sections 2.1 and 2.2 describecycle flow model and product model, respectively, and Sectionoutlines the integration mechanism for the two models.

A R T I C L E I N F O

Keywords:

Lifecycle

Design

CAD

A B S T R A C T

In product life cycle design, a designer should design both a product and its life cycle. Although

systems for product design are popular, there are no CAD systems for life cycle design. This p

proposes LC-CAD (Life Cycle-CAD) that represents a product and its life cycle in an integrated man

manages consistency between these two models, and describes changes of a product along its life c

(e.g., a component is shredded into fragments of metal in a recycling process). LC-CAD also evalu

environmental, economic, and other performance of designed life cycle using life cycle simulation

� 2012 C

Contents lists available at SciVerse ScienceDirect

CIRP Annals - Manufacturing Technology

journal homepage: http: / /ees.elsevier.com/cirp/default .asp

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optimization of their parameters. In such models, the relationshipbetween a product and its life cycle is implicit. Though PLM(product lifecycle management) involves correlating product andlife cycle data into one data architecture [11], its core concept is theconstruction of a computational environment that mediates the

Wethatrgy,* Corresponding author.

0007-8506/$ – see front matter � 2012 CIRP.

http://dx.doi.org/10.1016/j.cirp.2012.03.043

2.1. Life cycle flow model

In this paper, we define a product life cycle consisting oproduct and its life cycle flow. The life cycle flow is a networprocesses such as manufacturing, operation, logistics, use, mtenance, collection, remanufacturing, recycling, and disposal.

represent the life cycle flow by a life cycle flow model [13]

represents the flow of products, components, materials, ene

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Y. Umeda et al. / CIRP Annals - Manufacturing Technology 61 (2012) 175–178176

rmation and money among the processes in the form of acted graph (see Fig. 1).

Product model

e represent a product from three aspects of structure,etry, and attributes, and the product model consists of the

e sub-models as shown in Fig. 2.e describe the structure model as a graph that represents the

archy and connectivity among the product’s components. Weesent the geometry by solid models. The attribute modellves a set of attributes (e.g., constituent materials, lifetime,ht, price, and recyclability) of each component, each module,each product.ach node in the structure model denotes a component, aule, or a product, and is linked with its correspondentetric model and attributes. If a designer changes theetry of a component in a solid modeler, the attributive

es (e.g., weight) of the component are also updated and theectivity of the component to its neighboring components mayge.hese nodes are connected by two types of edges, i.e., hierarchyconnectivity. The hierarchal edges are directed links from ant node to its child nodes, meaning that the parent nodetes an assembly of the child nodes. The connectivity edgeste the connection types of fixation, motion constraint, signal

smission, power transmission, fluid transportation, etc. amongcomponents in the same hierarchy.

Integration of product and life cycle models

n order to represent and manage the relationship between theuct model and the life cycle flow model, we define an

gration scheme for the two. product changes throughout its life cycle as shown in Fig. 3. Inexample, some components are assembled into a module in aufacturing process, and the module is shredded and sorted

into fragment clusters in a recycling process. The integrated modelof the product and its life cycle flow should represent such statechanges by relating these two sub-models. To do so, we introduceanother edge type of ‘inter-model,’ which connects a node in theproduct structure model and an edge in the life cycle flow model.An inter-model edge represents which part of the product passesthrough which process of the flow model as shown in Fig. 4. In theintegrated model, state changes are represented as changes of theconnectivity, geometry, and attributes of the product modelthrough the processes of the life cycle flow model. Here, a change inconnectivity represents a change of assembly state of the product.In the example of Fig. 4, through the disassembly process (greenbox), the electrical module is disassembled into two units; viz.,control unit and camera unit. In this case, the input edge of thedisassembly process is connected with the module node (greencircle) by an inter-model link (green arrow) and its child nodes ofcamera unit and control unit are connected with the two outputedges of the disassembly process.

The geometry and attributes of a product may also be changedthrough the life cycle processes. In order to represent such changes,we introduce an edge type of ‘transformation’ in the structuremodel. The original node and its variant node are connected withthis type of edge. The two nodes linked by a transformation edgedenote the same entity in different states and do not coexist at thesame time. Then, a geometric or attributive change is representedas an alternation of the active node connected by the transforma-tion edge. In the example of Fig. 4, the shredding process (red box)changes the state of the control unit into shredded fragments andvoids original geometry of the component. To represent suchtransition between two states, two nodes of different attributes orgeometry are inserted into the product model, and they areconnected and alternated via a transformation edge.

In this way, a product and its changes along life cycle processesare formalized with the graph structure.

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Fig. 2. Product model. Fig. 4. Relationship between product and life cycle flow models.

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Y. Umeda et al. / CIRP Annals - Manufacturing Technology 61 (2012) 175–178 177

3. LC-CAD for product life cycle design

Based on the representational scheme defined in Section 2, wepropose an LC-CAD system that allows modeling, management,and evaluation of a product life cycle. Section 3.1 outlines themanagement scheme of consistency between a product model andits life cycle flow model, and Section 3.2 describes the evaluationmethod using LCS [8].

3.1. Consistency management between a product and its life cycle

The LC-CAD system manages consistency between a productmodel and its life cycle flow model through the topologicalstructure of the two sub-models connected by the inter-modeledges. Here, the term ‘consistency’ refers to the completion ofcorrespondence between the two sub-models. For this purpose, wedefine five correct patterns of correspondence between the nodesof the product model and the edges of the life cycle flow model asshown in Fig. 5. The two patterns in the upper part of this figuredenote disassembly and assembly of components through aprocess. The middle two denote sorting and merging of entities,e.g., sorting shredded plastics into clusters of the same materialtype. And the lower two are changing and not changing ofgeometry or attributes, e.g., a maintenance process changes aworn-out component to a new one, and storing a product inwarehouse does not change the state of the product.

These elemental patterns represent feasible transitions of aproduct’s states between input and output of a process. Thus, theentire structure consisting of a product model, a life cycle flowmodel, and inter-model edges must be composed only by theseprimitives. When the entire structure involves other topologicalpatterns, the system judges that the product life cycle model isinconsistent. This validation mechanism avoids designing infea-sible life cycles. Fig. 6 depicts some inconsistent relations of aproduct and its life cycle. We can find here that excess anddeficiency of edges in their topological structure cause missing orredundancy of product elements in the life cycle.

3.2. LCS-based evaluation of a product life cycle

LC-CAD supports the designer to evaluate the designed productlife cycle. For such evaluation, we employ LCS, which simulates theflow of products, materials, money, and information based ondiscrete event simulation techniques.

Since the main simulation model for LCS is the life cycle flmodel defined in Section 2.1, the life cycle can be simuladirectly and interactively from the LC-CAD model. Prodinformation in the LCS model imports the parameter valueprocess inputs and outputs, such as materials, weights, prices,

disassembly costs of input/output objects. They are supplied byproduct model via inter-model edges. Units of measurement sas CO2 emission intensity data for calculating environmental loand resource/energy consumptions can be imported from

databases [14]. As a result, the simulation subsystem allowsevaluation of the designed product life cycles from an integraview of environmental consciousness and economic profitabiliteach step of life cycle design. The evaluation results are usedanalyzing, comparing, and modifying design of the life cycle.

4. Case study

For verifying effectiveness of LC-CAD for supporting life cdesign, we executed a design modification of a cellular phone

its life cycle.Using LC-CAD, we first constructed the product model and

life cycle flow model based on the current cellular phone andrecycling system in Japan. In the life cycle flow, collected enduse products are shredded and smelted to extract only precimetals, such as gold and copper.

Next, we selected the remanufacturing strategy in whcellular phones are restored to like-new condition throreplacement of worn-out components, and changed the desof both the product and its life cycle to reduce its CO2 emissiand resource consumption without decreasing the current profithe manufacturer. Then, we modified the life cycle flow modeadapting to the remanufacturing strategy by adding the nclosed-loop, in which components other than worn-out ones (cases and buttons) are disassembled, inspected, and re-assembWorn-out components and components found to be defectivthe inspection process are shredded and sent to a materecycling process.

After the revision of the flow model, the system detecinconsistencies between the current product model and the nflow model for remanufacturing. As shown in Fig. 7, the origproduct model was not applicable to the revised disassemprocess because the body part going to the recycling process conot be separated from the electrical module that goes to

Process

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remanufacturing process. To resolve this inconsistency,

hierarchy, connectivity, and layout (geometry) of concercomponents were changed to enable this disassembly. Howethe system also revealed that the button unit lost the way torecycling process in the new flow model, meaning that this prodstructure also violated the primitive pattern defined in SectionHere, we added a separation process for sending the button unthe same shredding process as the other recyclable compone

Based on the representational scheme described in Section

the system shows a designer which component undergoes whprocess in which state, for checking the product’s suitability for

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Y. Umeda et al. / CIRP Annals - Manufacturing Technology 61 (2012) 175–178178

ess in terms of geometry and layout. For example, the systemlayed the assembly structure of the camera module in theection process, clarifying that the control board in the module

shielded by other parts and therefore difficult to inspect. Foring this problem, we changed the layout to expose the controld for inspection as shown in Fig. 8. Although change of theection process was also considered, LCS-based cost simulationted this alternative from an economic point of view. In this

, LC-CAD supported decision making at early design stage.

iscussions

he simulation results by LCS revealed that the designed lifee for remanufacturing offers the potential to reduce its CO2

ssions and resource consumption to 87% and 73%, respectively, the current life cycle while maintaining profits. Here we used

LCA data of cellular phones [15] for the calculation of CO2

ssions.s this new strategy requires structural changes to the productits life cycle, further assessment of its feasibility is needed toider, e.g., reliability, manufacturability, and market capability.

example, as remanufactured phones are not exactly the sameew products, in the case study we set their price and market

to 60% and 30% of those for brand-new products, respectively.e rates were taken as suppositions for the evaluation. Morerate simulation should be executed by adding precise dataed from detailed design at the later stage of life cycle design.C-CAD will be used to efficiently manage the consistency

the geometry and attributes of input/output objects of a processneed to be formalized.

6. Conclusion

The paper proposed a CAD system for integrated design of aproduct and its life cycle. The case study showed that LC-CADallows designers to model a product and its life cycle in anintegrated manner, manage consistency between these twomodels, and evaluate their environmental and economic perfor-mance by employing LCS. It is remarkable that the multiple statesof a product and their transitions during the life cycle are wellmanaged and visualized using the representational schemeproposed in this paper.

Future works include the development of feasibility assessmentschemes in consideration of various aspects of the product lifecycle and the integration of various eco-design methods into thisLC-CAD framework.

References

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[2] Hauschild MZ, Wenzel H, Alting L (1999) Life Cycle Design – A Route to theSustainable Industrial Culture? Annals of the CIRP 48(1):93–96.

[3] Hauschild MZ, Jeswiet J, Alting L (2004) Design for Environment? Do We Getthe Focus Right? Annals of the CIRP 53(1):1–4.

[4] Zussman E, Kriwet A, Seliger G (1994) Disassembly-Oriented AssessmentMethodology to Support Design for Recycling. Annals of the CIRP 43(1):9–14.

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[8] Umeda Y, Nonomura A, Tomiyama T (2000) Study on Life-cycle Design for thePost Mass Production Paradigm. AI EDAM-Artificial Intelligence for EngineeringDesign Analysis and Manufacturing 14(2):149–161.

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[11] Alemanni M, Destefanis F, Vezzetti E (2011) Model-based Definition Design inthe Product Lifecycle Management Scenario. International Journal of AdvancedManufacturing Technology 52(4):1–14.

[12] Takata S, Kimura T (2003) Life Cycle Simulation System for Life Cycle ProcessPlanning. Annals of the CIRP 52(1):37–40.

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een the product model and its life cycle flow model byking correspondence between the topology of the two models.ever, consistency from other aspects should be supported bysystem, such as component geometry and attributes, andking of their suitability to the life cycle processes. Thelopment of such management methods is one of our futures. To this end, schemes for describing process conditions for

[13] Fukushige S, Kunii E, Umeda Y (2011) A Design Support System forScenario-based Lifecycle Design. Proc. of ASME IDETC/CIE2011, DETC2011-47447 (CD-ROM).

[14] Inamura T, Umeda Y, Kondoh S, Takata S (2004) Proposal of Life CycleEvaluation Method for Supporting Life Cycle Design. Proc. of 6th Int. Conf.on EcoBalance, 43–46.

[15] Takeshima, A., Fujinami, T., Yamada, Y., 2005, A Life Cycle Assessment ofMobile Phones, Bachelor Thesis, Department of Environmental and Informa-tion Studies, Musashi Institute of Technology, http://www.yc.tcu.ac.jp/�itsubo-lab/reports/cs2005-c.pdf (in Japanese).