- Email: [email protected]
Enhancing disassembly and recycling planning using life-cycle analysis
ARTICLE IN PRESS
Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428 www.elsevier.com/locate/rcim
Enhancing disassembly and recycling planning using life-cycle analysis Tsai C. Kuo Department of Industrial Engineering and Management, Ming Hsin University of Science and Technology, Hsinchu, Taiwan, ROC Received 7 October 2005; accepted 14 November 2005
Abstract Both the general public and governmental agencies highly prioritize resource optimization (energy and material) and environmental issues such as ozone, acid rain and global warming in the life-cycle context. Disassembly and recycling are also increasingly important in most industrial countries due to the significant increase in the quantity of used products being discarded. Disassembly of used products has been recognized as necessary to make recycling economically viable in current state-of-the-art reprocessing technology. This emerging trend requires incorporating environmental considerations into design strategies. This study presents a graph-based heuristic method for disassembly analysis of end-of-life products, which incorporates the Eco-Design concept. Product components and their assembly relationships from the bill of material BOM are adopted to split the graph into sub-graphs denoting modular sub-assemblies. The life-cycle analysis LCA is then used to analyze disassembly trees, from which a disassembly sequence can be derived. Designers can use the analytical results to evaluate the dis-assemblability and recyclability of products when they are designed. r 2006 Elsevier Ltd. All rights reserved. Keywords: Life-cycle analysis; Disassembly planning; Recycling; Bill of material
1. Introduction Products were traditionally designed mainly to meet functional requirements, generally without considering recycling or environmental issues during the design process. That is, most companies did not consider methods of retiring end-of-life (EOL) products (e.g., reuse, disposal and recycling) and how they impacted on the environment. Modern environmental regulations and product take-back programs have led to a trend towards increasing the production, distribution, usage, and disposal of economically and ecologically sound products [1–3]. The environmental impact of these products results from interrelated decisions made at various life-cycle stages. Alting [4] first addressed recycling and environmental problems specifically within the life-cycle design (LCD) concept [also known as the life-cycle analysis (LCA), or environmentally conscious design and manufacturing (ECD&M)]. LCA is an effective means of identifying Tel.: +886 3 5593142 2149; fax: +886 3 5593142 3212.
E-mail address: [email protected]. 0736-5845/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.rcim.2005.11.014
environmental burdens during each phase of the whole product life cycle, which can reduce the environmental impact, such as global warming, and ozone problems [5]. The LCA emphasizes that products must be produced, distributed, used and disposed of or recycled without harming the environment in any phase. However, most products have previously considered the disassembly, recycling and environmental impact analysis separately. Thus, the aim of this study is to develop a full modeling technique that can provide effective and efficient disassembly analysis and recycling strategies to meet the requirements of current developments in recycling. This study presents an integrated disassembly and recycling model within LCA to perform disassembly and recycling planning for a product design. The components of a product and their assembly relationships are first obtained from the assembly bill of material (BOM) and transformed into a component-fastener graph. Second, the graph is split into sub-graphs representing modular subassemblies by a disassembly sequence and tree. Third, the disassembly BOM is presented and analyzed by LCA Finally, designers use the analytical results to evaluate the
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
421
Both LCA and ECD&M emphasize the urgency of starting to recycle EOL products, because recycling turns waste into useful products by reusing whole parts or subassemblies. For instance, electronic materials (gallium, germanium, silicon and indium) can be profitably recycled because of their high production cost. Many industrial processes have been presented for extracting these valuable elements from components on PCBs [6]. Two engineering technical problems, disassembly planning and recycling analysis, are inevitably confronted when systematically recycling these EOL products [7]. Disassembly planning and recycling strategies are two closely related tasks in recycling EOL products. Disassembly of used products is known to be needed to make recycling economically and environmentally viable in reprocessing technology, because most complex products cannot be recycled directly. Therefore, products must be disassembled, or dismantled into separate components or materials, to be recycled as secondary materials.
shredding. Scrap is compressed in shredders and fed into a drum, where it is ripped apart by a set of rotating hammers until it is sufficiently small to drop out of an output grid. Light-weight materials (e.g., textile or some plastics) are then separated from heavy weight materials (e.g., steel or other ferrous metals). The nondestructive disassembly process, allows complete material recycling of products, along with possible part and subassembly reuse or remanufacture [9]. However, some technical problems involved in the non destructive disassembly processes, such as the disassembly sequence, tools, process termination and cost, make the process difficult to implement systematically. Adequately reusing parts or subassemblies and recycling material can both significantly reduce waste generation, thereby increasing product environmental compatibility. Therefore, a comprehensive disassembly and recycling model must be developed to support real-world disassembly. This model should integrate disassembly planning, recycling strategies and the environmental impact of EOL products. Specifically, this model should identify the termination of the disassembly process, generate disassembly sequences, identify recycling methods, calculate recycling costs, evaluate the environmental impact, and provide design support for new products.
2.1. Disassembly planning
2.2. Recycling strategy
Disassembly attempts to increase the efficiency and economy of recycling. Brennan et al. [8] defined disassembly as ‘‘the processes of systematic removal of desirable constitute parts from an assembly while ensuring that there is no impairment of the parts due to the process’’. Components and materials can be removed in either of two ways, by destructive or non-destructive disassembly. The most common destructive disassembly method is
Seliger et al. [10] defined recycling as ‘‘recovering materials or components of a used product to make them available for new products.’’ Recycling can also be thought of as practical recycling technology, or remanufacturing EOL products into useful products. Recycling is different from reuse and remanufacturing, as indicate in Fig. 1 [11]. Recycling can reduce environmental strains caused by product use and production. On the input side, using
dis-assemblability and recyclability of products that they are designing. Desirable changes can then be made at an early design stage. 2. Background
Fig. 1. Different forms for recycling (Liu et al., [11]).
ARTICLE IN PRESS 422
T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
Table 1 The DEI scoring card
recycled goods reduces the amount of material needed. On the output side, recycling of unwanted output of production (internal recycling), and of scrapped products, both reduce the amount of waste resulting from production or consumption processes. Two engineering problems associated with design of recyclability (DFR) are dismantling techniques and recycling costs. Simon [12] noted that dismantling requires knowledge of the destination or recycling possibility of the component parts disassembled. However, recycling and reengineering techniques will have advanced between the time a product is designed and the time it reaches the end of its life. Simon suggested two solutions to this problem: (1) removing the most valuable parts first, and (2) maximizing the ‘‘yield’’ of each dismantling operation. Designing for ease of disassembly and recycling is a challenging problem to researchers and practitioners in the automotive industry. Das et al. [13] adopted the six disassembly costs, and formulated the disassembly effort index (DEI) to analyze the disassembly planning. These six costs are included in the disposal and disassembly processes: (1) product collection; (2) sorting into disassembly families; (3) product handling; (4) disassembly worker training and instructions; (5) product disassembly, and (6) part and material handling. Das et al. adopted the
DEI to consider the cost of categories (3) and (6) based on the following Table 1. 3. Disassembly and recycling-integration model This study presents an integrated approach to disassembly and recycling planning to perform disassembly and recycling planning based on the LCA. This method focuses on the disassembly and recycling planning during the product design stage, resulting in a disassembly tree. While the disassembly tree can be adopted to derive a series of disassembly and recycling plans, its major aim is to help designers evaluate the disassemblability and recyclability of the product being designed. Fig. 2 shows a flowchart of the proposed method. 3.1. Data input Several databases—BOM, material, assembly, and assembly tool—should be included when executing the disassembly and recycling planning model. (1) Assembly BOM. A production BOM is a part listing with specifications, and is a reference displaying the part name, code, specification and cost. In practice, this
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
423
Fig. 2. LCA based disassembly and recycling planning.
A
A (1, fAB (t)) 1
2
4
B
B
D
C
3
3
100
E
F
G 20 J
H
K
2 C
D 1
50
1
2
4
H
I 5 L
(20, fHJ (t))
10
J
M
(2, fHK (t)) K
(50,0) I (5, fHL (t)) L
(b)
(a)
Fig. 3. (a) Production BOM as a tree. (b) Recycling BOM as a tree.
information is adopted for system design, purchasing and inventory control. However, the counterparts of production BOMs are recycling BOMs, which are needed to calculate the quantities of fractions and materials resulting from disassembly. An arrow in a recycling BOM thus denotes the relationship type ‘‘is decomposed into’’. Figs. 3(a) and (b) show a production BOM and its recycling counterpart. The recyclable parts of the production BOM that are recyclable are shaded grey in Fig. 3(a). The two BOMs differ as follows. Part Code—Numbers or letters corresponding to a specific part. The code should match a code appearing on the working drawing, and is also adopted in inventory and data base management. Quantity—Number of parts needed to produce one unit. Description—Name of the part. Like the code, the name should correspond to the name that appears on the working drawing.
Dimensions—Finished dimension of the part. A standard format should be followed consistently when entering dimensions. (2) Material profile. Material containment is a very serious problem for the environment. An important aspect of sustainable development is conserving nonrenewable resources. To sustain the environment, manufacturers are encouraged to use environmentally friendly material or recycled content. This approach is feasible as long as substitution of recycled material with potential impurities is cost effective and does not compromise the quality of the final product. (3) Assembly relationship and method. The assembly relationship can be defined as a design element whose intended function or purpose is to maintain two design elements (e.g., components and subassemblies) together. Examples include screws, rivets and welding. Table 2 shows the assembly method. The current industry utilizes three connections material, friction, and positive connections. The effect of the assembly
ARTICLE IN PRESS 424
T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
Table 2 Common disassembly activities (Das et al. [13]) Unfastening processes (removal of the following) 1. Nail 2. Rivet 3. Screw 4. Retaining ring 5. Staple 6. Nuts and Bolts 7. Push on fastener 8. Spring toggle 9. Zipper and velcro 10. Cantilevered snapfit 11. Seam 12. Glue 13. Tape Disassembly process 1. Self removal of part 2. Axial part pull out 3. Levered removal 4. Hammered removal 5. Adhesive separation 6. Shearing cut 7. Saw cutting 8. Flame cutting 9. Crushing and bending 10. Shredding 11. Chemical dissolution 12. Suction and drainage 13. Drilling 14. Solder breakage 15. Drilling 16. Weld and solder breakage
rivets and inserts. The component-fastener graph is an undirected graph. While the vertices of the graph consist of component information, including its name, weight and material type, the edges consist of fastener information, including the number of fasteners, fastener type and the assembly method. Let M ¼ [mij] denote G’s adjacency matrix. Since G denotes an undirected graph, M denotes symmetric. Matrix M is defined as follows: 3 2 m11 m12 ::: m1n 7 6 6 m21 m22 ::: m2n 7 7 6 6 : : 7 : 7, M¼6 6 : : 7 : ::: 7 6 7 6 4 : : 5 : mn1 mn2 ::: mnn where mij ¼
8 > < 1;
if component i is connectedðassembledÞ to component j; otherwise:
> : 0; 2
3
E 1;1
E 1;2
::: E 1;j
6 E 2;1 6 6 6 : Ec ¼ 6 6 : 6 6 4 : E i;1
E 2;2 : :
::: E 2;j 7 7 7 : 7 7; : 7 ::: 7 7 : 5 ::: E i;j
: E i;2
where Eij ¼ 1 if Vi and Vj are connected, otherwise 0. method was evaluated. The assembly database included in this model was adopted to perform the disassembly analysis. (4) Disassembly activities. The disassembly activities were based on the assembly methods. Table 2 shows the unfastening and disassembly processes based on the assembly methods. The disassembly and recycling methods should be considered in order to disassemble efficiently and effectively when performing the disassembly and recycling planning.
Level 0
Level 1 E 211
V 211
V 21m
.. .
E 221
V 221
.. .
V 222
.. ... .
1
E11
V 12
E 222
3.2. Network analysis . E1k
Level q-1
Level q
.. .
E 2km
1
E12
...
. . .
V11
V0
The components of a product and their relationships can be represented by a component-fastener graph G ¼ (V,E). A component is a part of a product required for the product to function properly. The components are denoted using vertices V ¼ {v1, v2,y, vn}, where n denotes the number of components. Their relationships are represented by edges E ¼ {e1, e2,y, em}, where m denotes the number of edges. If two components vi and vj (i6¼j) are assembled together, then (vi, vj)AE; otherwise (vi, vj)eE. If i ¼ j, then (vi, vj)eE. Fasteners connect components together for the purpose of assembly. Examples of fasteners include screws,
Level 2
E 22m 2
q Eq (σq)1 E(σq)1 . q−1 V( ) . q−1 p .
Eq (σq)i
. . .
V 22m
2
.
E q−1 (q−1)p
.. .
.
.. .
.. .
Vq (σq)i
(CP)V q
(σq )
i
(CM−CS)
i
(CD)V q
(σq )
i
.. .
V 2k1 . . .
E 2k1 V 1k
E 2km V 2 km k
k
.. .
Fig. 4. A representation of the disassembly tree.
Vq (σq )
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
3.3. Disassembly sequence analysis To perform the disassembly planning and recycling analysis of an EOL product, a disassembly tree is constructed based on modularity analysis. A tree is defined as ‘‘a connected graph without circuit’’ [14]. A disassembly tree is defined as ‘‘a group of feasible disassembly sequences and the state of disassembly’’ [15]. In this proposed disassembly model, a disassembly tree not only denotes the disassembly sequences and stages, but also consists of the recycling method for each component. Specifically, the disassembly tree denotes the hierarchy of disassembly relationships and recycling methods for each part. A disassembly tree comprises of a parent component and children components. When the product’s structure has been clarified, not every disassembly operation is suitable
Ozone layer Depletion
Damage Fatalities
Heavy Metals Carcinogens CFC Pb Cd PAH VOC Dust DDT CO2 SO2 NO2 P
Health Impairment
Summer Smog
Ecoindicator
425
for it. Some disassembly operations are not possible because there are no physical relationships existing between the components, and others cannot be performed because the joints are fixed, e.g., welding or soldering making physical separation impossible. The sequence of disassembly can be denoted hierarchically by a disassembly tree, which identifies all major modules and components in the product. Each sub-graph denotes a module from the modularity analysis. These modules are the child vertices of the parent vertex. The fasteners that must be removed to obtain a child vertex (a module) are embedded in the edge connecting the child vertex to its parent. The componentfastener graph indicates that the most complex assembly relationship cut vertex is found and will be chosen as the base for the whole assembly. Then, the component-fastener graph and disassembly precedence matrices will be decomposed according to the modularity analysis. By evaluating the disassembly matrices based on the modularity analysis, the component will be disassembled from an un-constrained direction by using the graph-matrix algorithms (GMA), shown in Fig. 4. For further information about the network analysis and disassembly sequences generation, please refer to the Kuo et al. [16]. 3.4. LCA
Winter Smog Pesticides
The most significant challenge within the LCA framework is the assessment of the impact associated with environmental releases during the manufacturing, transport, usage and disposal of products. Impact analysis is a vast subject concerning the environmental health, or safety effect upon humans and ecosystems (e.g., land use restriction and resource depletion). The assessment of impacts is problematic because knowledge of complex physical and chemical phenomena is fairly poor. Impact analysis has in the past focused on risk analysis. Risk is the
Ecosystem
Green House Effect
impairment
Acidification Eutrophication
Fig. 5. LCA. Table 3 The product BOM of pair of roller skate (unit:g/pair) Part Name
Material
Forefoot Cuff Receiver
PP PU Fe:90% POM:10%
Strap
Fe:90% POM:10%
Nail, screw, pad Cradle Insole pad Chassis PU wheel Bearing Bearing spacer Brake support Brake pad Total weight (A)
Fe Nylon+glass fiber EVA Al PU Fe Al Nylon Rubber
Weight 190 236 27 3
% 7.20 8.95 1.02 0.11
59.4 6.6
2.25 0.25
174.1 504 40 358 704 184 16 47 88 2637.1
6.60 19.11 1.52 13.58 26.70 6.98 0.61 1.78 3.34
Remark Polypropylene Dry PU composite leather Billet Production
Nylon 66/glass fiber composite EVA foaming Al–Mg Dry PU composite leather Billet Production Al–Mg Nylon 66 fiber Thermoplastic Rubber (TPE)–ROC
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
426
possibility of an adverse outcome associated with an event or activity [17]. Indexing and scoring are the most common methods of impact analysis. Indexing and scoring are evaluated by subjective judgment to derive a numerical rating. These ‘‘scores’’ are rarely physically meaningful in an absolute sense, but can be adopted to distinguish between the relative environmental impact of alternative methods. Although these methods are very useful, they have often been faulted for inaccuracy and failure to account for important site properties Fig. 5. 4. Illustrations–Roller blades This study analyzed the disassembly and recycling planning of a pair of roller blades. The roller blade was separated into four modules based on the network analysis—body, base, breaks and wheels. Each module included the component name, number, material and weight, and the module data was be retrieved from the BOM database, as shown in Table 3. The data in Table 3 were retrieved from the assembly BOM including the part name, material and weight.
The part information could also be obtained from the CAD shown in Figs. 6 and 7. 4.1. Environmental impact analysis Table 4 shows the analysis of the contents of the assembly BOM based on the recyclable, potential recyclable and un-recyclable material. Therefore, the disassembly and recycling BOM (D&R BOM) was built and analyzed. The analysis indicates that the assembly BOM contained only 26.4% recyclable material, and hence 73.6% unrecyclable material, because the roller blade mainly comprised of polyurethane (PU) (about 38%), which cannot be re-melted or remolded, making it difficult to recycle. Additionally, the glass-fiber composite material is not suitable for recycling, since it reduces the safety and regeneration ability of the part. The recycled material comprised of about 32.2% metal and only 8% PP. Therefore, the design team should consider how to substitute the PU with PP since PP is easy to be recycled. The LCA was performed by Simpro 5.1. Only 93% of the material in the roller blade was used for the LCA calculation in this study, because the material, POM, used in the roller blade produced in Taiwan does not appear in the relevant LCA database. Therefore, the LCA for this material was not included in the Simpro 5.1 database, and the environmental impact analysis could be calculated only for 93%, as presented in Tables 5 and 6. 4.2. Modularity network analysis Fig. 8 shows the roller blade de-modularized based on the component fastener graph described by Kuo et al. [5,16]. The components C6, C7, and C12 denote the cut vertices that are the most connected parts in the roller blade, because once each component is removed, the graph can be separated as two or more modules. The fastener
Fig. 6. The roller-skate representation.
Roller Skate 1
1
Upper Wheel 1
Hard Content 1 5 Forefoot
(a)
1 3 Bottom foot
Upper Wheel
Base Wheel
Hard Content
Chassis Base
Break 1
1
1
Base Wheel 1
1
1 4 Soft Content
1 Receiver
1
1
1
1
1
1
1
4
1 Receiver
4 Soft Content
1
Chassis Base
Break 4
2
2
1 2 Cuff
13 Break Pad
Production BOM
12 Break Support
8-11 Wheel 1
6-7 Chassis
8-11 Wheel 1
(b) Fig. 7. Assembly BOM of roller skate.
Disassembly BOM
6-7 Chassis
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
data are also shown as follows. All modules base on the disassembly and recycling analysis are listed and discussed. (1) Body module. As shown in Fig. 8, the body module comprised of five components, v1, v2, y, v5. The graph analysis indicates that v5 was the cut vertex linked with component v6 in the base module. To disassemble the base and body modules easily, the connection between Table 4 Material analysis Material
Weight (g)
%
Recyclable material Un-recyclable material Potential Recyclable
1055.5 1581.6 405
26.4 73.6 15.4
Table 5 Material type Material Type
Weight (kg)
%
Remarks
Polypropylene Dry PU composite leather Billet Production Nylon 66/glass fibre composite EVA foaming Al–Mg Alloy Nylon 66 fibre Thermoplastic rubber (TPE)–ROC
PP PU FE Nylon+fiber glass
0.19 0.94 0.2704 0.504
8 38 11 21
EVA AL Nylon-66 Plastic TPE
0.04 0.374 0.047 0.088
2 15 2 4
LCA calculation (b) Summarization
2453.4 93
POM is not calculated in the LCA
427
v5 and v6 should be easily disconnected or disassembled. Additionally, the disassembly procedure and tools should be easily processed to simplify the disassembly process. (2) Base module. Although only two components v5 and v6 were composed in this module, the aim of this module is to protect safety during the skating exercise. The base module is closely connected with the wheel, body and break modules. (3) Break module. The break module should generally be easily separated from the main body of the roller blade, since it is changed regularly. Moreover, some users take the break module out from the main body. Therefore, the fasteners between the break and wheels should be designed to allow easy separation from the body. (4) Wheel base module. The critical component in this module is the v11, since it is connected not only with the wheel base, but also with the break pad by rivets. Additionally, the break supports (v12) and the break pads (v13) are connected together (by OR with OR using) screws.
5. Conclusions Disassembly of used products is well understood to be needed to make recycling economically and environmentally viable in the current state of the art of reprocessing technology, because most complex products cannot be recycled directly. This study presents a graph-based heuristic method to perform disassembly analysis for rollerskate products. A disassembly tree is generated based on modularity analysis (disassembly oriented) and disassembly precedence analysis. By examining the disassembly tree, designers can evaluate how easily a designed product
Table 6 Environmental impact by using LCA Environmental impact
CML criteria indices
Eco-indicator 95 charact. criteria indices
Eco-indicator 95 val. criteria indices
Value
Unit
Value
Unit
Value
Unit
Green house effect Eutrophication Ozone depletion Acid precipitation Eco-toxicity aquatic ECA Eco-toxicity terrest. ECT Human toxicity nonbio resource depletion Heavy metals Carcinogens Winter smog Summer smog Pesticide Energy Solid waste Water
2.31E+01 2.90E02 3.07E01 2.83E+02
Kg CO2 Kg (PO4)3 Kg CFC11 Kg SO2 mg Cr
2.31E+01 2.79E02 2.39E05 2.99E01
Kg Kg Kg Kg
CO2 (PO4)3 CFC11 SO2
4.40E03 3.66E03 2.59E03 2.65E02
minipoint minipoint minipoint minipoint
3.09E01
g 2.27E06 1.62E07 2.50E01 1.20E03
Kg Pb Kg PAH Kg SO2 PCOPkg C2H4
5.53E04 1.49E04 1.38E02 7.26E04
minipoint minipoint minipoint minipoint
4.73E+02 2.01E+03 4.48E+02
MJ kg kg
4.73E+02 2.01E+03 4.48E+02
minipoint minipoint minipoint
4.73E+02 2.01E+03 4.48E+02
MJ kg kg
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
428
References
Body Module
1
2
5
3
4 8
Base Module
6
9
7
10 11 12
13 Wheel Module
Break Module Fig. 8. Modular analysis.
can be disassembled, and can then make changes to group components with similar life cycle and similar material type into the same disassembly module. Finally, the proposed disassembly model provides the environmental impact indication and design support for newly designed products. The disassembly model supports the designer early in the design cycle to allow determining the probable effects of prospective design decisions before adverse environmental impacts occur. The information needed in this disassembly model can be found in the proposed database and database management systems which are the first to fully incorporate the product structure, impact on the environmental life cycle, environmental material, and cost into the disassembly and recycling process.
Acknowledgment The authors would like to thank the National Science Council of the Republic of China, Taiwan for financially supporting this research under Contract no. NSC 89-2213E-159-029.
[1] Fishbein BK, McGarry LS, Dillon PS. Leasing: A Step Toward Producer Responsibility. Inform Inc.; 2000. [2] Sony, Sony Green Partner Activities, Developments in the Green Partner Environmental Quality Approval Program, Sony Corporation Procurement Center, February 1, 2003. [3] DEC, Department of Environment and Conservation, 2004. Extended Producer Responsibility Priority Statement, Waste Management Science of the Department of Environment and Conservation. [4] Alting L. Designing for a lifetime. Manufacturing breakthrough, May/ June 1993:29–33. [5] Kuo TC, Zhang HC, Huang SH. A graph-based disassembly planning for end-of-life electromechanical products. Int. J. Prod. Res. 2000;38(5):993–1007. [6] Roy R. End-of-life electronic equipment waste, technical report. Center for the Exploitation of Science and Technology (CEST); 1991 November. [7] Ishii K, Eubanks F. Life Cycle Evaluation of Mechanical Systems. Proceedings of the 1993 NSF design and manufacturing systems conference/SME 1993;1:575–9. [8] Brennan L, Gupta SM, Taleb KN. Operations Planning Issues in an Assembly/Disassembly Environment. Int. J. Oper. Prod. Manage. 1994;14(9):57–67. [9] Jovane F, Alting L, Armillotta A, Eversheim W, Feldmann K, Seliger G, Roth N. Key issue in product life cycle: disassembly. Ann. CIRP 1993;42(1):1–13. [10] Seliger G, Zussman E, Kriwet A. Recycling consideration in the system life-cycle. Proceedings of the Seminar on Life cycle engineering Arw 1993. [11] Liu ZF, Liu XP, Wang SW, Liu GF. Recycling Strategy and a Recyclability Assessment Model Based on an Artificial Neural Network. J. Mater. Process. Technol. 2002;129:500–6. [12] Simon M. Design for dismantling. Professional engineering 1991:20–2. [13] Das SK, Yedlarajiha P, Narendra R. An approach for estimating the end-of-life product disassembly effort and cost. Int J Prod Res 2000;38(3):657–73. [14] Thulasiraman K, Swamy MNS. Graphs: theory and algorithms. New York: Wiley; 1992. [15] Zhang D, Kuo TC, Zhang HC. Life Cycle Engineering: Concepts and Researches, Manufacturing Science and Engineering. American Society of Mechanical Engineers 1995;2–2:827–46. [16] Kuo TC, Zhang HC, Huang SH. A graph-based disassembly planning for end-of-life electromechanical products. Int. J. Prod. Res. 2000;38(5):993–1007. [17] Fiksel J. Design for environment: creating eco-efficient product and processes. New York: McGraw-Hill; 1996.
Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428 www.elsevier.com/locate/rcim
Enhancing disassembly and recycling planning using life-cycle analysis Tsai C. Kuo Department of Industrial Engineering and Management, Ming Hsin University of Science and Technology, Hsinchu, Taiwan, ROC Received 7 October 2005; accepted 14 November 2005
Abstract Both the general public and governmental agencies highly prioritize resource optimization (energy and material) and environmental issues such as ozone, acid rain and global warming in the life-cycle context. Disassembly and recycling are also increasingly important in most industrial countries due to the significant increase in the quantity of used products being discarded. Disassembly of used products has been recognized as necessary to make recycling economically viable in current state-of-the-art reprocessing technology. This emerging trend requires incorporating environmental considerations into design strategies. This study presents a graph-based heuristic method for disassembly analysis of end-of-life products, which incorporates the Eco-Design concept. Product components and their assembly relationships from the bill of material BOM are adopted to split the graph into sub-graphs denoting modular sub-assemblies. The life-cycle analysis LCA is then used to analyze disassembly trees, from which a disassembly sequence can be derived. Designers can use the analytical results to evaluate the dis-assemblability and recyclability of products when they are designed. r 2006 Elsevier Ltd. All rights reserved. Keywords: Life-cycle analysis; Disassembly planning; Recycling; Bill of material
1. Introduction Products were traditionally designed mainly to meet functional requirements, generally without considering recycling or environmental issues during the design process. That is, most companies did not consider methods of retiring end-of-life (EOL) products (e.g., reuse, disposal and recycling) and how they impacted on the environment. Modern environmental regulations and product take-back programs have led to a trend towards increasing the production, distribution, usage, and disposal of economically and ecologically sound products [1–3]. The environmental impact of these products results from interrelated decisions made at various life-cycle stages. Alting [4] first addressed recycling and environmental problems specifically within the life-cycle design (LCD) concept [also known as the life-cycle analysis (LCA), or environmentally conscious design and manufacturing (ECD&M)]. LCA is an effective means of identifying Tel.: +886 3 5593142 2149; fax: +886 3 5593142 3212.
E-mail address: [email protected]. 0736-5845/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.rcim.2005.11.014
environmental burdens during each phase of the whole product life cycle, which can reduce the environmental impact, such as global warming, and ozone problems [5]. The LCA emphasizes that products must be produced, distributed, used and disposed of or recycled without harming the environment in any phase. However, most products have previously considered the disassembly, recycling and environmental impact analysis separately. Thus, the aim of this study is to develop a full modeling technique that can provide effective and efficient disassembly analysis and recycling strategies to meet the requirements of current developments in recycling. This study presents an integrated disassembly and recycling model within LCA to perform disassembly and recycling planning for a product design. The components of a product and their assembly relationships are first obtained from the assembly bill of material (BOM) and transformed into a component-fastener graph. Second, the graph is split into sub-graphs representing modular subassemblies by a disassembly sequence and tree. Third, the disassembly BOM is presented and analyzed by LCA Finally, designers use the analytical results to evaluate the
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
421
Both LCA and ECD&M emphasize the urgency of starting to recycle EOL products, because recycling turns waste into useful products by reusing whole parts or subassemblies. For instance, electronic materials (gallium, germanium, silicon and indium) can be profitably recycled because of their high production cost. Many industrial processes have been presented for extracting these valuable elements from components on PCBs [6]. Two engineering technical problems, disassembly planning and recycling analysis, are inevitably confronted when systematically recycling these EOL products [7]. Disassembly planning and recycling strategies are two closely related tasks in recycling EOL products. Disassembly of used products is known to be needed to make recycling economically and environmentally viable in reprocessing technology, because most complex products cannot be recycled directly. Therefore, products must be disassembled, or dismantled into separate components or materials, to be recycled as secondary materials.
shredding. Scrap is compressed in shredders and fed into a drum, where it is ripped apart by a set of rotating hammers until it is sufficiently small to drop out of an output grid. Light-weight materials (e.g., textile or some plastics) are then separated from heavy weight materials (e.g., steel or other ferrous metals). The nondestructive disassembly process, allows complete material recycling of products, along with possible part and subassembly reuse or remanufacture [9]. However, some technical problems involved in the non destructive disassembly processes, such as the disassembly sequence, tools, process termination and cost, make the process difficult to implement systematically. Adequately reusing parts or subassemblies and recycling material can both significantly reduce waste generation, thereby increasing product environmental compatibility. Therefore, a comprehensive disassembly and recycling model must be developed to support real-world disassembly. This model should integrate disassembly planning, recycling strategies and the environmental impact of EOL products. Specifically, this model should identify the termination of the disassembly process, generate disassembly sequences, identify recycling methods, calculate recycling costs, evaluate the environmental impact, and provide design support for new products.
2.1. Disassembly planning
2.2. Recycling strategy
Disassembly attempts to increase the efficiency and economy of recycling. Brennan et al. [8] defined disassembly as ‘‘the processes of systematic removal of desirable constitute parts from an assembly while ensuring that there is no impairment of the parts due to the process’’. Components and materials can be removed in either of two ways, by destructive or non-destructive disassembly. The most common destructive disassembly method is
Seliger et al. [10] defined recycling as ‘‘recovering materials or components of a used product to make them available for new products.’’ Recycling can also be thought of as practical recycling technology, or remanufacturing EOL products into useful products. Recycling is different from reuse and remanufacturing, as indicate in Fig. 1 [11]. Recycling can reduce environmental strains caused by product use and production. On the input side, using
dis-assemblability and recyclability of products that they are designing. Desirable changes can then be made at an early design stage. 2. Background
Fig. 1. Different forms for recycling (Liu et al., [11]).
ARTICLE IN PRESS 422
T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
Table 1 The DEI scoring card
recycled goods reduces the amount of material needed. On the output side, recycling of unwanted output of production (internal recycling), and of scrapped products, both reduce the amount of waste resulting from production or consumption processes. Two engineering problems associated with design of recyclability (DFR) are dismantling techniques and recycling costs. Simon [12] noted that dismantling requires knowledge of the destination or recycling possibility of the component parts disassembled. However, recycling and reengineering techniques will have advanced between the time a product is designed and the time it reaches the end of its life. Simon suggested two solutions to this problem: (1) removing the most valuable parts first, and (2) maximizing the ‘‘yield’’ of each dismantling operation. Designing for ease of disassembly and recycling is a challenging problem to researchers and practitioners in the automotive industry. Das et al. [13] adopted the six disassembly costs, and formulated the disassembly effort index (DEI) to analyze the disassembly planning. These six costs are included in the disposal and disassembly processes: (1) product collection; (2) sorting into disassembly families; (3) product handling; (4) disassembly worker training and instructions; (5) product disassembly, and (6) part and material handling. Das et al. adopted the
DEI to consider the cost of categories (3) and (6) based on the following Table 1. 3. Disassembly and recycling-integration model This study presents an integrated approach to disassembly and recycling planning to perform disassembly and recycling planning based on the LCA. This method focuses on the disassembly and recycling planning during the product design stage, resulting in a disassembly tree. While the disassembly tree can be adopted to derive a series of disassembly and recycling plans, its major aim is to help designers evaluate the disassemblability and recyclability of the product being designed. Fig. 2 shows a flowchart of the proposed method. 3.1. Data input Several databases—BOM, material, assembly, and assembly tool—should be included when executing the disassembly and recycling planning model. (1) Assembly BOM. A production BOM is a part listing with specifications, and is a reference displaying the part name, code, specification and cost. In practice, this
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
423
Fig. 2. LCA based disassembly and recycling planning.
A
A (1, fAB (t)) 1
2
4
B
B
D
C
3
3
100
E
F
G 20 J
H
K
2 C
D 1
50
1
2
4
H
I 5 L
(20, fHJ (t))
10
J
M
(2, fHK (t)) K
(50,0) I (5, fHL (t)) L
(b)
(a)
Fig. 3. (a) Production BOM as a tree. (b) Recycling BOM as a tree.
information is adopted for system design, purchasing and inventory control. However, the counterparts of production BOMs are recycling BOMs, which are needed to calculate the quantities of fractions and materials resulting from disassembly. An arrow in a recycling BOM thus denotes the relationship type ‘‘is decomposed into’’. Figs. 3(a) and (b) show a production BOM and its recycling counterpart. The recyclable parts of the production BOM that are recyclable are shaded grey in Fig. 3(a). The two BOMs differ as follows. Part Code—Numbers or letters corresponding to a specific part. The code should match a code appearing on the working drawing, and is also adopted in inventory and data base management. Quantity—Number of parts needed to produce one unit. Description—Name of the part. Like the code, the name should correspond to the name that appears on the working drawing.
Dimensions—Finished dimension of the part. A standard format should be followed consistently when entering dimensions. (2) Material profile. Material containment is a very serious problem for the environment. An important aspect of sustainable development is conserving nonrenewable resources. To sustain the environment, manufacturers are encouraged to use environmentally friendly material or recycled content. This approach is feasible as long as substitution of recycled material with potential impurities is cost effective and does not compromise the quality of the final product. (3) Assembly relationship and method. The assembly relationship can be defined as a design element whose intended function or purpose is to maintain two design elements (e.g., components and subassemblies) together. Examples include screws, rivets and welding. Table 2 shows the assembly method. The current industry utilizes three connections material, friction, and positive connections. The effect of the assembly
ARTICLE IN PRESS 424
T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
Table 2 Common disassembly activities (Das et al. [13]) Unfastening processes (removal of the following) 1. Nail 2. Rivet 3. Screw 4. Retaining ring 5. Staple 6. Nuts and Bolts 7. Push on fastener 8. Spring toggle 9. Zipper and velcro 10. Cantilevered snapfit 11. Seam 12. Glue 13. Tape Disassembly process 1. Self removal of part 2. Axial part pull out 3. Levered removal 4. Hammered removal 5. Adhesive separation 6. Shearing cut 7. Saw cutting 8. Flame cutting 9. Crushing and bending 10. Shredding 11. Chemical dissolution 12. Suction and drainage 13. Drilling 14. Solder breakage 15. Drilling 16. Weld and solder breakage
rivets and inserts. The component-fastener graph is an undirected graph. While the vertices of the graph consist of component information, including its name, weight and material type, the edges consist of fastener information, including the number of fasteners, fastener type and the assembly method. Let M ¼ [mij] denote G’s adjacency matrix. Since G denotes an undirected graph, M denotes symmetric. Matrix M is defined as follows: 3 2 m11 m12 ::: m1n 7 6 6 m21 m22 ::: m2n 7 7 6 6 : : 7 : 7, M¼6 6 : : 7 : ::: 7 6 7 6 4 : : 5 : mn1 mn2 ::: mnn where mij ¼
8 > < 1;
if component i is connectedðassembledÞ to component j; otherwise:
> : 0; 2
3
E 1;1
E 1;2
::: E 1;j
6 E 2;1 6 6 6 : Ec ¼ 6 6 : 6 6 4 : E i;1
E 2;2 : :
::: E 2;j 7 7 7 : 7 7; : 7 ::: 7 7 : 5 ::: E i;j
: E i;2
where Eij ¼ 1 if Vi and Vj are connected, otherwise 0. method was evaluated. The assembly database included in this model was adopted to perform the disassembly analysis. (4) Disassembly activities. The disassembly activities were based on the assembly methods. Table 2 shows the unfastening and disassembly processes based on the assembly methods. The disassembly and recycling methods should be considered in order to disassemble efficiently and effectively when performing the disassembly and recycling planning.
Level 0
Level 1 E 211
V 211
V 21m
.. .
E 221
V 221
.. .
V 222
.. ... .
1
E11
V 12
E 222
3.2. Network analysis . E1k
Level q-1
Level q
.. .
E 2km
1
E12
...
. . .
V11
V0
The components of a product and their relationships can be represented by a component-fastener graph G ¼ (V,E). A component is a part of a product required for the product to function properly. The components are denoted using vertices V ¼ {v1, v2,y, vn}, where n denotes the number of components. Their relationships are represented by edges E ¼ {e1, e2,y, em}, where m denotes the number of edges. If two components vi and vj (i6¼j) are assembled together, then (vi, vj)AE; otherwise (vi, vj)eE. If i ¼ j, then (vi, vj)eE. Fasteners connect components together for the purpose of assembly. Examples of fasteners include screws,
Level 2
E 22m 2
q Eq (σq)1 E(σq)1 . q−1 V( ) . q−1 p .
Eq (σq)i
. . .
V 22m
2
.
E q−1 (q−1)p
.. .
.
.. .
.. .
Vq (σq)i
(CP)V q
(σq )
i
(CM−CS)
i
(CD)V q
(σq )
i
.. .
V 2k1 . . .
E 2k1 V 1k
E 2km V 2 km k
k
.. .
Fig. 4. A representation of the disassembly tree.
Vq (σq )
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
3.3. Disassembly sequence analysis To perform the disassembly planning and recycling analysis of an EOL product, a disassembly tree is constructed based on modularity analysis. A tree is defined as ‘‘a connected graph without circuit’’ [14]. A disassembly tree is defined as ‘‘a group of feasible disassembly sequences and the state of disassembly’’ [15]. In this proposed disassembly model, a disassembly tree not only denotes the disassembly sequences and stages, but also consists of the recycling method for each component. Specifically, the disassembly tree denotes the hierarchy of disassembly relationships and recycling methods for each part. A disassembly tree comprises of a parent component and children components. When the product’s structure has been clarified, not every disassembly operation is suitable
Ozone layer Depletion
Damage Fatalities
Heavy Metals Carcinogens CFC Pb Cd PAH VOC Dust DDT CO2 SO2 NO2 P
Health Impairment
Summer Smog
Ecoindicator
425
for it. Some disassembly operations are not possible because there are no physical relationships existing between the components, and others cannot be performed because the joints are fixed, e.g., welding or soldering making physical separation impossible. The sequence of disassembly can be denoted hierarchically by a disassembly tree, which identifies all major modules and components in the product. Each sub-graph denotes a module from the modularity analysis. These modules are the child vertices of the parent vertex. The fasteners that must be removed to obtain a child vertex (a module) are embedded in the edge connecting the child vertex to its parent. The componentfastener graph indicates that the most complex assembly relationship cut vertex is found and will be chosen as the base for the whole assembly. Then, the component-fastener graph and disassembly precedence matrices will be decomposed according to the modularity analysis. By evaluating the disassembly matrices based on the modularity analysis, the component will be disassembled from an un-constrained direction by using the graph-matrix algorithms (GMA), shown in Fig. 4. For further information about the network analysis and disassembly sequences generation, please refer to the Kuo et al. [16]. 3.4. LCA
Winter Smog Pesticides
The most significant challenge within the LCA framework is the assessment of the impact associated with environmental releases during the manufacturing, transport, usage and disposal of products. Impact analysis is a vast subject concerning the environmental health, or safety effect upon humans and ecosystems (e.g., land use restriction and resource depletion). The assessment of impacts is problematic because knowledge of complex physical and chemical phenomena is fairly poor. Impact analysis has in the past focused on risk analysis. Risk is the
Ecosystem
Green House Effect
impairment
Acidification Eutrophication
Fig. 5. LCA. Table 3 The product BOM of pair of roller skate (unit:g/pair) Part Name
Material
Forefoot Cuff Receiver
PP PU Fe:90% POM:10%
Strap
Fe:90% POM:10%
Nail, screw, pad Cradle Insole pad Chassis PU wheel Bearing Bearing spacer Brake support Brake pad Total weight (A)
Fe Nylon+glass fiber EVA Al PU Fe Al Nylon Rubber
Weight 190 236 27 3
% 7.20 8.95 1.02 0.11
59.4 6.6
2.25 0.25
174.1 504 40 358 704 184 16 47 88 2637.1
6.60 19.11 1.52 13.58 26.70 6.98 0.61 1.78 3.34
Remark Polypropylene Dry PU composite leather Billet Production
Nylon 66/glass fiber composite EVA foaming Al–Mg Dry PU composite leather Billet Production Al–Mg Nylon 66 fiber Thermoplastic Rubber (TPE)–ROC
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
426
possibility of an adverse outcome associated with an event or activity [17]. Indexing and scoring are the most common methods of impact analysis. Indexing and scoring are evaluated by subjective judgment to derive a numerical rating. These ‘‘scores’’ are rarely physically meaningful in an absolute sense, but can be adopted to distinguish between the relative environmental impact of alternative methods. Although these methods are very useful, they have often been faulted for inaccuracy and failure to account for important site properties Fig. 5. 4. Illustrations–Roller blades This study analyzed the disassembly and recycling planning of a pair of roller blades. The roller blade was separated into four modules based on the network analysis—body, base, breaks and wheels. Each module included the component name, number, material and weight, and the module data was be retrieved from the BOM database, as shown in Table 3. The data in Table 3 were retrieved from the assembly BOM including the part name, material and weight.
The part information could also be obtained from the CAD shown in Figs. 6 and 7. 4.1. Environmental impact analysis Table 4 shows the analysis of the contents of the assembly BOM based on the recyclable, potential recyclable and un-recyclable material. Therefore, the disassembly and recycling BOM (D&R BOM) was built and analyzed. The analysis indicates that the assembly BOM contained only 26.4% recyclable material, and hence 73.6% unrecyclable material, because the roller blade mainly comprised of polyurethane (PU) (about 38%), which cannot be re-melted or remolded, making it difficult to recycle. Additionally, the glass-fiber composite material is not suitable for recycling, since it reduces the safety and regeneration ability of the part. The recycled material comprised of about 32.2% metal and only 8% PP. Therefore, the design team should consider how to substitute the PU with PP since PP is easy to be recycled. The LCA was performed by Simpro 5.1. Only 93% of the material in the roller blade was used for the LCA calculation in this study, because the material, POM, used in the roller blade produced in Taiwan does not appear in the relevant LCA database. Therefore, the LCA for this material was not included in the Simpro 5.1 database, and the environmental impact analysis could be calculated only for 93%, as presented in Tables 5 and 6. 4.2. Modularity network analysis Fig. 8 shows the roller blade de-modularized based on the component fastener graph described by Kuo et al. [5,16]. The components C6, C7, and C12 denote the cut vertices that are the most connected parts in the roller blade, because once each component is removed, the graph can be separated as two or more modules. The fastener
Fig. 6. The roller-skate representation.
Roller Skate 1
1
Upper Wheel 1
Hard Content 1 5 Forefoot
(a)
1 3 Bottom foot
Upper Wheel
Base Wheel
Hard Content
Chassis Base
Break 1
1
1
Base Wheel 1
1
1 4 Soft Content
1 Receiver
1
1
1
1
1
1
1
4
1 Receiver
4 Soft Content
1
Chassis Base
Break 4
2
2
1 2 Cuff
13 Break Pad
Production BOM
12 Break Support
8-11 Wheel 1
6-7 Chassis
8-11 Wheel 1
(b) Fig. 7. Assembly BOM of roller skate.
Disassembly BOM
6-7 Chassis
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
data are also shown as follows. All modules base on the disassembly and recycling analysis are listed and discussed. (1) Body module. As shown in Fig. 8, the body module comprised of five components, v1, v2, y, v5. The graph analysis indicates that v5 was the cut vertex linked with component v6 in the base module. To disassemble the base and body modules easily, the connection between Table 4 Material analysis Material
Weight (g)
%
Recyclable material Un-recyclable material Potential Recyclable
1055.5 1581.6 405
26.4 73.6 15.4
Table 5 Material type Material Type
Weight (kg)
%
Remarks
Polypropylene Dry PU composite leather Billet Production Nylon 66/glass fibre composite EVA foaming Al–Mg Alloy Nylon 66 fibre Thermoplastic rubber (TPE)–ROC
PP PU FE Nylon+fiber glass
0.19 0.94 0.2704 0.504
8 38 11 21
EVA AL Nylon-66 Plastic TPE
0.04 0.374 0.047 0.088
2 15 2 4
LCA calculation (b) Summarization
2453.4 93
POM is not calculated in the LCA
427
v5 and v6 should be easily disconnected or disassembled. Additionally, the disassembly procedure and tools should be easily processed to simplify the disassembly process. (2) Base module. Although only two components v5 and v6 were composed in this module, the aim of this module is to protect safety during the skating exercise. The base module is closely connected with the wheel, body and break modules. (3) Break module. The break module should generally be easily separated from the main body of the roller blade, since it is changed regularly. Moreover, some users take the break module out from the main body. Therefore, the fasteners between the break and wheels should be designed to allow easy separation from the body. (4) Wheel base module. The critical component in this module is the v11, since it is connected not only with the wheel base, but also with the break pad by rivets. Additionally, the break supports (v12) and the break pads (v13) are connected together (by OR with OR using) screws.
5. Conclusions Disassembly of used products is well understood to be needed to make recycling economically and environmentally viable in the current state of the art of reprocessing technology, because most complex products cannot be recycled directly. This study presents a graph-based heuristic method to perform disassembly analysis for rollerskate products. A disassembly tree is generated based on modularity analysis (disassembly oriented) and disassembly precedence analysis. By examining the disassembly tree, designers can evaluate how easily a designed product
Table 6 Environmental impact by using LCA Environmental impact
CML criteria indices
Eco-indicator 95 charact. criteria indices
Eco-indicator 95 val. criteria indices
Value
Unit
Value
Unit
Value
Unit
Green house effect Eutrophication Ozone depletion Acid precipitation Eco-toxicity aquatic ECA Eco-toxicity terrest. ECT Human toxicity nonbio resource depletion Heavy metals Carcinogens Winter smog Summer smog Pesticide Energy Solid waste Water
2.31E+01 2.90E02 3.07E01 2.83E+02
Kg CO2 Kg (PO4)3 Kg CFC11 Kg SO2 mg Cr
2.31E+01 2.79E02 2.39E05 2.99E01
Kg Kg Kg Kg
CO2 (PO4)3 CFC11 SO2
4.40E03 3.66E03 2.59E03 2.65E02
minipoint minipoint minipoint minipoint
3.09E01
g 2.27E06 1.62E07 2.50E01 1.20E03
Kg Pb Kg PAH Kg SO2 PCOPkg C2H4
5.53E04 1.49E04 1.38E02 7.26E04
minipoint minipoint minipoint minipoint
4.73E+02 2.01E+03 4.48E+02
MJ kg kg
4.73E+02 2.01E+03 4.48E+02
minipoint minipoint minipoint
4.73E+02 2.01E+03 4.48E+02
MJ kg kg
ARTICLE IN PRESS T.C. Kuo / Robotics and Computer-Integrated Manufacturing 22 (2006) 420–428
428
References
Body Module
1
2
5
3
4 8
Base Module
6
9
7
10 11 12
13 Wheel Module
Break Module Fig. 8. Modular analysis.
can be disassembled, and can then make changes to group components with similar life cycle and similar material type into the same disassembly module. Finally, the proposed disassembly model provides the environmental impact indication and design support for newly designed products. The disassembly model supports the designer early in the design cycle to allow determining the probable effects of prospective design decisions before adverse environmental impacts occur. The information needed in this disassembly model can be found in the proposed database and database management systems which are the first to fully incorporate the product structure, impact on the environmental life cycle, environmental material, and cost into the disassembly and recycling process.
Acknowledgment The authors would like to thank the National Science Council of the Republic of China, Taiwan for financially supporting this research under Contract no. NSC 89-2213E-159-029.
[1] Fishbein BK, McGarry LS, Dillon PS. Leasing: A Step Toward Producer Responsibility. Inform Inc.; 2000. [2] Sony, Sony Green Partner Activities, Developments in the Green Partner Environmental Quality Approval Program, Sony Corporation Procurement Center, February 1, 2003. [3] DEC, Department of Environment and Conservation, 2004. Extended Producer Responsibility Priority Statement, Waste Management Science of the Department of Environment and Conservation. [4] Alting L. Designing for a lifetime. Manufacturing breakthrough, May/ June 1993:29–33. [5] Kuo TC, Zhang HC, Huang SH. A graph-based disassembly planning for end-of-life electromechanical products. Int. J. Prod. Res. 2000;38(5):993–1007. [6] Roy R. End-of-life electronic equipment waste, technical report. Center for the Exploitation of Science and Technology (CEST); 1991 November. [7] Ishii K, Eubanks F. Life Cycle Evaluation of Mechanical Systems. Proceedings of the 1993 NSF design and manufacturing systems conference/SME 1993;1:575–9. [8] Brennan L, Gupta SM, Taleb KN. Operations Planning Issues in an Assembly/Disassembly Environment. Int. J. Oper. Prod. Manage. 1994;14(9):57–67. [9] Jovane F, Alting L, Armillotta A, Eversheim W, Feldmann K, Seliger G, Roth N. Key issue in product life cycle: disassembly. Ann. CIRP 1993;42(1):1–13. [10] Seliger G, Zussman E, Kriwet A. Recycling consideration in the system life-cycle. Proceedings of the Seminar on Life cycle engineering Arw 1993. [11] Liu ZF, Liu XP, Wang SW, Liu GF. Recycling Strategy and a Recyclability Assessment Model Based on an Artificial Neural Network. J. Mater. Process. Technol. 2002;129:500–6. [12] Simon M. Design for dismantling. Professional engineering 1991:20–2. [13] Das SK, Yedlarajiha P, Narendra R. An approach for estimating the end-of-life product disassembly effort and cost. Int J Prod Res 2000;38(3):657–73. [14] Thulasiraman K, Swamy MNS. Graphs: theory and algorithms. New York: Wiley; 1992. [15] Zhang D, Kuo TC, Zhang HC. Life Cycle Engineering: Concepts and Researches, Manufacturing Science and Engineering. American Society of Mechanical Engineers 1995;2–2:827–46. [16] Kuo TC, Zhang HC, Huang SH. A graph-based disassembly planning for end-of-life electromechanical products. Int. J. Prod. Res. 2000;38(5):993–1007. [17] Fiksel J. Design for environment: creating eco-efficient product and processes. New York: McGraw-Hill; 1996.