a framework for virtual disassembly analysis

A framework for virtual disassembly analysis

HARI SRINIVASAN, N. SHYAMSUNDAR and RAJIT GADH

I-CARVE Lab, Department of Mechanical Engineering, University of Wisconsin-Madison,Madison, WI 53706, USA

Received September 1996 and accepted March 1997

Product reuse or recyclability is enhanced by designing the product for inexpensive and e�-cient disassembly. However, accomplishing enhanced product design requires design for dis-

assembly (DFD) tools. This paper presents a disassembly framework that consists of designmodules; both of these are embodied in the geometric DFD tool. These modules consist ofdi�erent tasks including: selection of the appropriate disassembly method; producing an op-

timized disassembly sequence; evaluating a disassembly sequence for cost; producing designchange recommendations. These considerations make a product easier to disassemble andtherefore have potential bene®t to the environment.

Keywords: De-manufacturing, design for disassembly, design for environment and product

design

1. Introduction

Today, both consumer demand and government legislationrequire that manufacturers reduce the quantities of man-ufacturing waste generated. Both environmental concernsand rising product disposal cost have triggered customerpressure for more environmentally friendly products(Wittenberg, 1992). In recent years, product disposal costshave increased signi®cantly as land®ll and incinerationcapacities are rapidly depleted. Governmental action en-compasses both legislation and purchasing programs.Legislative actions include disposal bans for speci®cproducts. Conversely, purchasing programs favor productswhich are reusable or which have recycled content. How-ever, as a result of both these economic and legislative re-strictions, a ®rm's future competitiveness in world marketsdepends upon making environmental issues a central con-cern (Hoo et al., 1990; Byrne and Deeb, 1993).

1.1. Environmental impact of products

Signi®cant emphasis is being placed worldwide on thestudy of the environmental impact of products (Enviro-sense, 1995a). For example, the Dutch have implementedan assertive national environmental policy called the GreenPlan. They are also ®nding that development of e�cientand environmentally sound products may boost theircompanies' ability to compete in international markets

(GNET, 1995). Generally, governments attempt to makeindustry responsible for disposal of their products by re-quiring auto manufacturers to build auto-disassemblyplants. For example, in 1991 the Japanese Ministry of In-ternational Trade and Industry issued a regulation pro-moting not only the use of recycled materials in speci®cdurable items but also the recyclability of those items(Envirosense, 1995a, b). Signi®cant emphasis on reuse/re-cycling in the USA is realized by several research reports(Pohlen and Theodore, 1992; RHW News, 1993; Enviro-sense, 1995a).Given that the emphasis on recycled products will only

increase in the future (Kochan, 1995), organizations muststart becoming conscious of the need to design productsthat are environmentally friendly (CenCITT, 1995). Theapplication domains ± recycling, reuse, refurbishing andmaintenance ± bene®t if products can be disassembledeasily and cheaply (Thierry et al., 1993).

1.2. Software tool for designers

Design-for-environment (DFE) follows the engineeringconcepts of concurrent engineering, design for manufac-turing (DFM) and design for disassembly (DFD) (USEPA,1997). In DFE initiatives, environmental considerations arethe main focus of product design (Parker et al., 1995).However, before products can be developed in an envi-ronmentally sound way, designers must understand therelationship between a product and the environment. Theyalso need to use recycled materials and make recyclable

Journal of Intelligent Manufacturing (1997) 8, 277±295

0956-5515 Ó 1997 Chapman & Hall

products. A designer can increase the chances of a productbeing reused/recycled by initially designing the product fordisassembly (Zussmann et al., 1994; Olsen and Sutherland,1996; SUN, 1996).Disassembly is de®ned as the process of separating

components of a product. Demanufacturing is the processof disassembling products and then reusing, recycling orrefurbishing them. There are two ways to analyze for de-manufacturing. Figure 1a shows mode 1 of de-manufac-turing analysis where the product is not analyzed for dis-assembly before production. Because the product is notdesigned for disassembly, the disassembly evaluation has tobe performed at the end of its life-cycle (Ishii, 1995; Zhanget al., 1995). This could result in uneconomical and time-consuming disassembly. The end-cycle application inFig. 1a refers to de-manufacturing applications such asrecycling and reuse.Figure 1b shows mode 2 of de-manufacturing analysis.

In this case, the virtual prototype, the computer-aided de-sign (CAD) model of the product, is analyzed for disas-sembly before production (virtual disassembly). Thisanalysis could result both in the reduction of the product'sdisassembly cost and time spent on maintenance, and alsoincrease its recyclability at the end of its life.Until recently, mode 1 was the most commonly used

industrial practice despite mode 2 being a more e�cientmeans of disassembly. Mode 2 allows designers to evaluate

design options in a virtual environment without buildingan actual prototype. Therefore, a disassembly software toolneeds to be developed which integrates ease of disassemblyinto product design to e�ectively reuse and recycle mate-rials (Wittenberg, 1992). Our research work is on the de-velopment of a disassembly tool that relies on geometricinformation.

2. Related work

This section discusses the state of (1) industrial de-manu-facturing practice; (2) research into de-manufacturing anddisassembly.

2.1. Current state of industrial practice

Each step of industrial production generates waste thatcould be reused (GNET, 1995). To o�set this waste, man-ufacturers are beginning to implement environmentallyresponsible processes such as DFD and product steward-ship. In addition, smaller entrepreneurs make money bybrokering waste from one company as input to another.Another approach recycles existing waste into new prod-ucts and is being explored extensively (Motorola, 1996).IBM has established initiatives for designing disassembl-

able products, with reusable components and recycled ma-

Fig. 1. De-manufacturing analysis. (a) Mode 1; (b) mode 2.

278 Srinivasan et al.

terials. For example, the time required to disassemble thenew IBM Thinkpad laptop models is measured and trackedagainst target times (IBM, 1996). Xerox has also adopted aDFE approach. The recycling management organizationdeveloped guidelines which include materials selection andengineering techniques to facilitate disassembly for re-manufacturing purposes (Envirosense, 1995b).In 1992, the Chrysler Corporation, Ford Motor Com-

pany and General Motors Corporation joined forces in avehicle recycling partnership (VRP). The VRP's objectivesinclude benchmarking existing dismantling technology,development of improved dismantling protocols, anddemonstration of promising recycling technologies(Chrysler, 1995). Vehicle manufacturers have speci®callytargeted plastics ± approximately 30% of the automotiveshredder residue (ASR) ± for special recycling attentionbecause plastics are becoming the most commonly usedautomotive material (GM, 1994). Designers and engineersanalyze new car and truck development for virtual disas-sembly and recyclability (Ford, 1996).Industries analyze products for easy disassembly in order

to reuse/recycle the components. However, unlike researchinstitutions, they remain focused on developing guidelinesfor speci®c products rather than covering products of thesame domain. In addition, they tend to emphasize manualrather than automated disassembly.

2.2. Current research status

Both the potential for assembly modeling in product de-velopment (Whitney, 1996) and the growing importance ofenvironmentally conscious product design have resulted ina signi®cant amount of research into the areas of DFA,DFD and DFE. This section reviews state-of-the-art re-search into:

(1) Assembly/disassembly;(2) Disassembly sequence generation;(3) Disassemblability analysis;(4) Path generation;(5) Disassembly evaluation;(6) Other DFD-related areas such as DFE tools, end-of-

life disassembly, design for material recovery and roboticdisassembly.

The work to date has focused on disassembly sequencing,disassembly path planning and the evaluation toolsdevelopment. Boothroyd and Alting (1992) have reviewedDFA methods that have been developed over the past 15years and discuss the current research trends in DFD.Gupta and McLean (1996) and Jovane et al. (1993) haveprovided an overview of the ongoing research in productdisassembly and also present the topics and trends for fu-ture activities. Penev and Ron (1996) have reviewed theexisting theories for disassembly sequences and analyze themethods for the creation of an e�ective disassembly strat-

egy. Hrinyak et al. (1996) have examined the existing dis-assembly software tools available to designers for inclusionin their design processes. Kirby and Wadehra (1993) havediscussed the DFE factors that should be considered indesign of plastic parts for disassembly. In addition, theyreviewed the material selection, design concepts, fasteningand joining for disassembly.There exists extensive research on disassembly/assembly

sequence analysis. A disassembly/assembly sequence isde®ned as the order in which the components are disas-sembled/assembled. Researchers have suggested severalapproaches to determine disassembly/assembly sequences:

(1) Non-directional blocking graphs (Wilson and La-tombe, 1994);

(2) Constraint and contact geometry (Woo and Dutta,1991; Dutta and Woo, 1992; Mattikalli and Khosla, 1992;Wolter et al., 1996);

(3) Planners speci®cally designed for assembly se-quencing (Yan and Gu, 1995);

(4) Unconstrained directed graphs (Lapemere and ElMaraghy, 1992);

(5) Precedence relations (Yokota and Brough, 1992).

However, key di�erences between assembly and disassem-bly, such as irreversible operations including welding, riv-etting or breakage of components (Lee and Gadh, 1996),and selective disassembly, which requires only a portion ofan assembly to be disassembled (Srinivasan and Gadh,1997), suggests that the most economical assembly se-quence need not be the most economical disassembly se-quence. Moreover, the di�erences between assembly anddisassembly analysis make a separate study of productdisassemblability essential.Several approaches have been developed to determine the

disassemblability of product geometry and generation ofdisassembly sequence. Disassemblability refers to whether aselected component is removable from an assembly. Wooand Dutta (1991) have developed an algorithm to determinethe disassemblability of a 1-disassemblable component byconsidering the faces of the component which mate with therest of the assembly. In a later disassembly study, Dutta andWoo (1992) describe identifying a sub-assembly to initiatethe disassembly process for a 2.5-dimensional (2.5D) par-allel assembly. Beasley and Martin (1993) considered thegeneration of disassembly motion for voxelized models ofobjects. Other disassemblability and disassembly sequencetechniques include:

(1) Knowledge-based rules (Feldman and Scheller, 1994;Shin and Cho, 1994);

(2) Arti®cial intelligence approach (Spicer and Wang,1995b);

(3) Simulation (Li et al., 1995; Vujosevic et al., 1995);(4) Disassembling in a virtual environment (Siddique

and Rosen, 1996);

A framework for virtual disassembly analysis 279

(5) Contact geometry and metrics for non-destructivedisassembly (Shyamsundar et al., 1996a, b: Srinivasanet al., 1997);

(6) Layered graph and metrics for selective disassembly(Srinivasan and Gadh, 1997);

(7) Interlocking and contact geometry for destructivedisassembly (Lee and Gadh, 1996)

These existing approaches aim to minimize the disassemblycost by optimizing the disassembly sequence.Several approaches are suggested by researchers to de-

termine the disassembly path. The disassembly path is de-®ned as the 3D path along which a component isdisassembled from an assembly. Xu et al. (1995) have ad-dressed the problem of geometric path determination re-quired to remove a portion of the assembly contained in acavity within the parent assembly. In this work, all possiblegeometric paths are identi®ed by generating the partialmedial axis of the free space within the assembly. An op-timal path is found using a graph search technique. Hal-perin (1994) has studied partitioning an assembly intoseveral sub-assemblies. The concept of non-directionalblocking graph is extended to handle a compound removalpath for assembly partitioning. Other noted work in as-sembly/disassembly sequence and path planning ®elds islisted in the assembly planning bibliography (IEEE Ro-botics and Automation Society, 1996; Robotics Resources,1996; Wilson, 1996; Wolter, 1996).Once the disassembly sequence and paths are known, the

disassembly process needs to be evaluated for either cost,time or design e�ectiveness. This evaluation assesses theproduct design for disassembly and design for environ-ment. Several existing evaluation schemes are listed below.Kroll (1996) has developed a rating scheme for disassemblyevaluation based on the di�culty scores of each task inorder to determine the overall design e�ectiveness of aproduct. Bras and Emblemsvag (1995) have estimated thecost incurred by di�erent designs based on activity-based-costing (ABC). The suitability of ABC is explored in thecontext of design for product retirement. Other evaluationtechniques are based on:

(1) Energy and entropy for disassembly (Suga et al.,1996);

(2) Analytical hierarchy process approach (Lou et al.,1996)

(3) Simulation techniques (Boks et al., 1996);(4) Time standard data charts (Subramani and Dew-

hurst, 1994);(5) Scoring method (Lowe and Niku, 1995).

These evaluation techniques are useful to the designer inidentifying weaknesses in the design and comparing alter-native designs.On the other hand, several applications speci®c to recy-

cling/service and DFD related approaches have been pro-posed including:

(1) Software tools for DFE (Navin-Chandra, 1991,1993; Chen et al., 1993; Spath et al., 1995; Spicer andWang, 1995a);

(2) Robotic disassembly (Ansens et al., 1994; Tani, 1995,1996; Weigl, 1996);

(3) End-of-life approaches for disassembly (Zussmannet al., 1994; Girard and Boothroyd, 1995; Shu and Flowers,1995; Geiger and Zussmann, 1996; Harjula et al., 1996;Zhang et al., 1996);

(4) Product retirement analysis (Amezquita et al., 1995;Ishii et al., 1995; Ishii and Lee, 1996);

(5) Recyclability and material recovery (Spath, 1994;Johnson and Wang, 1995a, b; Wang and Johnson 1995;Coulter et al., 1996).

Although DFD is a strong and growing ®eld, the existingresearch still has several important limitations. Researchershave focused on the development of DFD research withoutsigni®cantly analyzing the 3D geometric disassembly ofproducts. Furthermore, the design modules and the prob-lem areas in building an automated geometry-based dis-assembly tool have yet to be analyzed. The designrequirements for de-manufacturing include guidance onmaterial selection and engineering techniques to facilitatedisassembly (CenCITT, 1995). This paper presents a dis-assembly framework that consists of design modules; bothof these are embodied in the geometric DFD tool. More-over, this virtual disassembly tool can be applied to 3Dassembly design.The rest of the paper is organized as follows: Section 3

presents the DFD framework and Section 4 de®nes thedi�erent disassembly methods. The design modules forvirtual disassembly analysis are discussed in Sections 5 to 8followed by an illustration of DFD modules in Section 9,with an example. Section 10 presents the discussion onDFD framework.

3. DFD framework

This section presents a geometric design for disassemblyframework. The DFD framework, shown in Fig. 2,identi®es the abstract design modules that need to be de-veloped to build a geometric virtual disassembly tool.These modules (software programs) are: (I) knowledge-base creation; (II) disassembly method selection; (III) dis-assembly analysis; (IV) design analysis. A brief introduc-tion to the design modules are presented in this sectionfollowed by a detailed analysis in Sections 5 to 8. Thenomenclature used in the current research is shown inFig. 2.

3.1. Module I. Knowledge base creation

The ®rst design module in the disassembly analysis of Aconsists of the formation of the knowledge base rules, R,


from the user requirements, UR, and a pre-existing data-base, DB. The knowledge base, R, de®nes: (1) the com-ponents to be disassembled, CS; (2) the Ôobjectivevariables', OV; (3) Ôrelative importance', RI, of objectivevariables; and (4) constraints, C, on the given disassemblyrequired for analysis.

3.2. Module II. Disassembly method selection

The input to this design module is R and A; the output isthe disassembly method DM. The selection of the appro-priate DM is based on: (1) disassemblability analysis; (2) R.The possibility of di�erent DMs for a given A is done by a

Fig. 2. DFD framework.


disassemblability analysis, whereas R imposes restrictionson DM selection.

3.3. Module III. Disassembly analysis

During disassembly analysis, the component optimal dis-assembly sequence DSo and disassembly path DPo aredetermined, followed by the evaluation of disassemblyparameters such as disassembly cost and time.

3.4. Module IV. Design analysis

During design analysis, the product design is rated fordisassembly which is followed by design change recom-mendations DR. These recommendations are for thepurpose of making the product easy to disassemble (andtherefore bene®cial to the environment).

4. Classi®cation of disassembly

This section de®nes the various DMs needed in this re-search. There are several DMs (Fig. 3a) based on the dis-assembly of a component Ci from A. They are: (1) 1- orm-disassembly; (2) direct or indirect disassembly; (3)sequential or parallel disassembly; (4) monotonic or non-monotonic disassembly; (5) complete or selective disas-sembly; (6) destructive or non-destructive disassembly.These classi®cations are presented in detail below.

4.1. 1-vs m-disassembly

Ci in A is classi®ed as m-disassemblable or 1-disassembl-able based on the number of linear motions required todisassemble Ci. Ci is m-disassemblable if m-continuouslinear motions are needed to remove Ci from A. In Fig. 3b,disassembling C2 from A cannot be performed in one linearmotion. A single linear motion would result in the collisionof C2 with C1. Therefore, C2 is m-disassemblable. InFig. 3c, disassembling C3 from the assembly can be per-formed in one single linear motion. Hence C3 is 1-disassemblable.

4.2. Direct vs indirect disassembly

Ci is classi®ed as directly or indirectly disassemblable basedon the number of components that need to be removed todisassemble Ci. Ci is directly disassemblable if it can beremoved from A without removing other components.Otherwise it is indirectly disassemblable. Disassembling C4

from A (Fig. 3d) requires no disassembly of other compo-nents. Thus C4 is directly disassemblable. Disassembling C3

from A, however requires disassembly of C4 before disas-sembly of C3. Therefore C3 is indirectly disassemblable.

4.3. Sequential vs parallel disassembly

Based on the number of components that are disassembledat a time, the disassembly sequence is classi®ed as se-quential or parallel disassembly. In a sequential disassem-bly sequence, only one component is removed from A at atime. In a parallel disassembly, several components areremoved from A simultaneously. For example, to disas-semble C3 from A shown in Fig. 3d, if C4 is disassembled®rst followed by C3 then the disassembly sequence is se-quential. Instead, if the sub-assembly fC2; C3; C4g is dis-assembled as a single group, followed by disassembly of C3

from the sub-assembly, then the disassembly sequence isparallel. For the disassembly of A shown in Fig. 3e, allthree components must be removed simultaneously todisassemble C1 or C2 or C3. This example illustrates theneed for parallel disassembly because it is the only practicalmethod to disassemble this A.

4.4. Monotonic vs non-monotonic disassembly

A disassembly sequence is classi®ed as monotonic or non-monotonic depending upon whether disassembling Ci in Arequires total or partial disassembly of other Cis in A. Adisassembly of Ci from A is total if Ci is removed out of theconvex hull of A. In monotonic disassembly, the compo-nents are totally removed from A. Conversely, non-monotonic disassembly requires partial disassembly of oneor more components. For example, in the A shown inFig. 3f, C3 can be disassembled after removing the hinge,followed by removing C1 and C2. This type of disassemblysequence is monotonic. Component C3 can also be disas-sembled by moving C1 and C2 to an intermediate position,followed by the disassembly of C3. This type of disassemblysequence is non-monotonic.

4.5. Complete vs selective disassembly

A disassembly sequence is classi®ed as selective or completebased on whether all components fCig of A or a subset offCig in A are disassembled. Complete disassembly occurswhen all fCig are disassembled. Selective disassembly oc-curs only when a subset of fCig are removed from A.

4.6. Destructive vs non-destructive disassembly

A disassembly method is classi®ed as destructive/non-de-structive depending upon whether any component is de-stroyed/not destroyed. In non-destructive disassembly, noneof the components of A are destroyed during disassembly.However, if one or more components are destroyed then thedisassemblymethod is destructive disassembly. For examplein Fig. 3d, disassembling C3, by disassembling C4 ®rst fol-lowed by C3 is non-destructive disassembly, as no compo-


Fig. 3. (a) Disassembly classi®cation; (b) m-disassembly; (c) 1-disassembly; (d) sequential; (e) parallel; (f) non-monotonic; (g) destructive.


nents are destroyed. Disassembly of C2 from A, shown inFig. 3g, by destroying C3 is destructive disassembly.

5. Design module I. Knowledge base creation

The ®rst design module (Fig. 2) is for the purpose of au-tomatic creation of a knowledge base, which requires theformation of R from A, DB and UR.A contains the geometric information about the com-

ponents and includes information about the mating faces,®ts and fasteners between the components. The DB con-sists of an MD, ED and AD. The MD contains informa-tion concerning material cost and material properties. TheED contains information about: (1) hazardous materialsand their environmental impact; (2) whether a material canbe either recycled or reused. The AD contains informationabout: (1) components requiring grouping (for example,disassembling the automotive engine as a single subas-sembly to disassemble a component inside the engine); (2)the speci®c hierarchy of the components (for example,disassembling the pipe before disassembling the enginevalve); (3) joints and fasteners. The UR may include re-quirements such as minimal cost and time.R consists of: (1) CS, component set or sub-assemblies

that need to be disassembled; (2) OVs, such as disassembly

cost and time; (3) RI of OVs (for example, the disassemblycost is of higher precedence compared to disassembly time,hence RI value of disassembly cost will be higher than RIof disassembly time); (4) C, such as constraints on disas-sembly method selection and disassembly path.The R is modeled in terms of CS, OV, RI and C which

ensures that component disassembly satis®es both user andenvironmental requirements. An example of R for Ashown in Fig. 4, is (partial listing):

(1) CS: bushing (brass) wears quickly and needs frequentmaintenance. Hence the component for maintenance ap-plication for disassembly analysis is C2;

(2) OV: the component should be easily accessible;(3) C: no component can be destroyed.

Automation of knowledge base creation requires the use ofexpert systems or neural-network-based systems.

6. Design module II. Disassembly method selection

The second design module (Fig. 2) is for the selection of anappropriate DM satisfying: (1) assembly geometry; (2) R.The possibility of di�erent DMs for a given A is done bydisassemblability analysis, which depends on the geometryof A. The R impose restriction on DM selection. The se-

Fig. 3f-g

Fig. 4. Exploded view of left-end bearing assembly (from Earle, 1996, p. 350).


lection of the appropriate DM is required as the disas-sembly analysis di�ers for various DMs. The inputs of thismodule are R and A; the output is DM.Prior to the selection of the appropriate DM, a discus-

sion is required on the de®nition of disassemblability �D�,i.e. the geometric consideration used to disassemble acomponent. Sections 6.1, and 6.2 present the disassem-blability analysis and the selection of the appropriate DMfor disassembly analysis.

6.1. Disassemblability

Ci is disassemblable (D is TRUE) if it can be removed fromthe rest of A. Disassemblability of Ci depends on the stateof A. For example in Fig. 4, D is TRUE for C3 and for C2 itis FALSE. C2 can be disassembled only after disassemblingC3. Similarly for Fig. 5a, D is TRUE for C2.

The geometrical information, such as mating faces andvisibility maps (Woo, 1994), is used to determine D of Ci

(Woo and Dutta, 1991). The disassembly directions for Ci

with respect to its mating faces are mapped onto aGaussian sphere for 3D assemblies (and for 2D assembliesthe disassembly directions are mapped onto a Gaussiancircle). The disassembly directions for each mating faceintersect to obtain the resultant disassembly direction for a1-disassemblable component. Figure 5b shows the disas-sembly directions of C2 from the mating faces M1 and M2 ofC1 (Fig. 5a). When considering only M1, the disassemblydirection for C2 is d1. When considering M2, the direction isd2. The resultant disassembly direction for C2 is the inter-section of d1 and d2. This is shown as dr. If dr is null then Dis FALSE for the component. In general, if a componentcan be disassembled from A consisting of m-disassemblablecomponents without disturbing other components then thecomponent is disassemblable.

Fig. 5. (a) Test assembly; (b) disassemblability of C2.

Fig. 6. (a) 1-disassembly; (b) 2-disassembly; (c) Interlocking property between C2 and C3.


6.2. Selection of appropriate disassembly

The criteria in selection of the appropriate DM are: (1)disassemblability analysis; (2) R.The component disassemblability is used as a tool to

identify all possible DMs for a given A. Some of the criteriafor identi®cation of possible DMs basedon disassemblability analysis of a component are discussedbelow:

(1) For Ci to be disassembled, if D is FALSE then Ci canbe disassembled only by indirect disassembly. Otherwiseeither direct or indirect DMs are possible;

(2) If the disassembly directions of Ci, computed, basedon Gaussian sphere abstraction (also termed local acces-sibility directions), are also global disassembly directions,then Ci is 1-disassemblable. This can be identi®ed bymoving Ci along the computed local disassembly direc-tion(s) and checking for possible intersection with A. If Ci

can be removed outside the convex hull of A without anyintersection with A, then Ci is 1-disassemblable. Figures 6(aand b) illustrate this analysis for 1- and 2-disassembly;

(3) Destructive disassembly is the only option if Ci to bedisassembled is: (i) welded or riveted (this information isavailable from the CAD model); (ii) interlocking with other

components. Determination of the interlocking propertybetween two components (D is FALSE between these twocomponents) is illustrated in Fig. 6c.

Identi®cation of non-monotonic and parallel disassemblybased on disassemblability analysis are presented in Mat-tikalli and Khosla (1992) and Dutta and Woo (1992) res-pectively.Once the geometric analysis for possible DM choices is

performed, the appropriate DM for disassembly analysis isselected based on R. An example of a simpli®ed car modelcontaining an instrument panel, car seats, door and rest ofthe body is shown in Fig. 7a in which the di�erent possibleDM choices to disassemble the front panel and car seatsare illustrated. The possible DM choices are:

Case 1. Selective, monotonic, non-destructive, indirectand 1-disassembly: Fig. 7b shows the non-destructivemonotonic disassembly of car seats and front panel aftercompletely disassembling the side door of the car;

Case 2. Selective, non-monotonic, non-destructive, in-direct and 1-disassembly: Fig. 7c shows the non-monotonicnon-destructive disassembly of the car front panel and carseats after opening (non-monotonic disassembly) the car'sside door;

Fig. 7. (a) Conceptual design of a car; (b) DM: case 1; (c) DM: case 2; (d) DM: case 3.

(a) (b)

(c) (d)


Case 3. Selective, monotonic, destructive, indirect and 1-disassembly: Fig. 7d shows the monotonic destructive dis-assembly of car seats and front panel after cutting (de-stroying) the car roof and disassembling the seats and panelfrom the top.

From the possible DM choices, the one that best satis®es Ris selected. For example, with R being `component shouldbe easily accessible' and `minimum possible disassemblycost', the preferred DM is case 3. The DM 's shown inFig. 7b (case 1) and 7c (case 2), are the less preferred so-lutions due to the low component accessibility.The general criteria of selection between 1- or m-disas-

sembly, direct or indirect disassembly, sequential orparallel disassembly, monotonic or non-monotonic disas-sembly, selective or complete disassembly, destructive ornon-destructive disassembly, when both options are pos-sible, depend on R. Some of the general criteria are asfollows:

(1) A 1-disassemblable component will be disassembledas an m-disassemblable component, if advantage exists byincreasing the complexity of the disassembly path. Forexample, in Fig. 8a, 2-disassembly is preferred as it pro-vides better clearance for C1;

(2) A component requires indirect disassembly if its di-rect disassembly might result in interaction with hazardousmaterial along the direct disassembly path (Fig. 8b);

(3) Parallel disassembly is chosen only if a set of com-ponents can be disassembled by parallel disassembly. Thiswould of course require that facilities be available to dis-assemble more than one component at a time. In othercases, sequential disassembly is selected;

(4) A non-monotonic disassembly is preferred overmonotonic disassembly sequence, if the component of in-terest can be disassembled easily by non-monotonic disas-sembly;

(5) Choosing between complete and selective disassem-bly depends on application requirements. For example, inFig. 8c for recycling application the requirement is toseparate the materials, i.e disassembly of C3 and C5 fromA. In this case selective disassembly remains a better optioncompared to complete disassembly as the number ofcomponents that need to be disassembled from A are lessthan the number of components in A;

(6) A destructive disassembly sequence is preferred overnon-destructive, if by destroying cheap component (e.g. afastener), components can be disassembled with minimalexpense/time.

7. Design module III. Disassembly analysis

The disassembly analysis module (Fig. 2) consists of twosub-modules: (1) optimum disassembly sequence and pathgeneration; (2) disassembly parameter evaluation. The in-puts to this module are A;DM ;CS;OV ;RI and C. Theoutput is DD, which contains information about DSo andDPo and the evaluated disassembly parameter values.

7.1. Optimum disassembly sequence and path generation

This sub-module generates the DSo and DPo for the se-lected DM. As the DSo generation (in general) is combi-

Fig. 8. (a) 1-and m-disassembly; (b) direct and indirect disassembly; (c) lifting device assembly (from Earle, 1996, p. 344).


natorial (Wilson and Latombe, 1994), knowledge-basedapproaches are used to reduce the complexity. The disas-sembly sequence for the selected DM is optimized withrespect to an objective function OF. An OF is formulatedfrom the metrics ± a non-dimensional parameter ± con-structed for every OV and RI of OV. An example A isshown in Fig. 9a to illustrate our approach for DSo gen-eration. The DM selected is complete disassembly.

Metric Me1 � Ac=Tc �1�Metric Me2 � �Wt ÿ Wc�=Wt �2�

Objective function OF � f1 �Me1 � f2 �Me2 �3�where

Ac: accessibility of the component of interest;Tc: maximum possible accessibility;Wc: weight of the component of interest;Wt: total weight of the assembly or sub-assembly;f1; f2: RI for accessibility and weight.

Equations 1 and 2 are the metrics formulated with theOV being `accessibility' and `weight'. Equation 3 de®nesthe OF. A component with maximum Me1 is one that hasmaximum Ac. Similarly, a component with maximum Me2value has the minimum Wc. The DSo selected is one thatmaximizes the OF value (the component that is disassem-bled is the one with maximum OF value). The DSo with f1

and f2 being 0.8 and 0.2 is fC6; C5; C4;C3; C2; C1g, whichis shown in Fig. 9b.

7.2. Disassembly parameter evaluation

The DSo and DPo generation is followed by the disas-sembly parameter evaluation. This sub-module evaluatesdesigns for parameters, such as disassembly cost and time.The inputs to this disassembly evaluation sub-module areDSo and DPo. The evaluated parameters, such as disas-sembly cost and time, are the outputs from this sub-mod-ule. An equation to evaluate the disassembly time fromKroll (1996) is Equation 4. The DRo includes di�culty incomponent accessibility, positioning, force, base time andother factors. The summation sign in Equation 4 refers tosummation over component accessibility, positioning,force, base time and other factors:

DT ��X�

DR� TR�ÿ 5�

XTR�� 1:04

� �TM � 0:9��4�

where

DT : disassembly time;DR : di�culty rating;TR : number of task repetitions;TM : number of tool hand manipulations.

Fig. 9. (a) Flange coupling assembly; (b) complete DSo and DPo for ¯ange coupling.


The disassembly sequence typically a�ects the cost ofdisassembly. Depending upon the DM the cost of DSocould vary. Two typical cost models, one for complete andone for selective DSo are shown in Equations 5 and 6:

CDC � Function of �AC;CP ; TI ;ED; . . .� �5�SDC � Function of �ND;AC; VO;CP ; TI ; . . .� �6�

where

CDC : complete disassembly cost;SDC: selective disassembly cost;AC : accessibility;CP : complexity of the disassembly path;TI : time required for disassembly operation;ED : ease of disassembly;VO : volume of the components;ND : number of components disassembled.

Based on observation, the CDC increases with CP ; TIand decreases with AC;ED; SDC increases with ND;VO;CP ; TI and decreases with AC;ED.

8. Design module IV. Design analysis

The design analysis module (shown in Fig. 2) consists oftwo sub-modules: (1) design rating for disassembly; (2)design change recommendations. The inputs, to this mod-ule are A and DD. The outputs, are RV and DR.

8.1. Design rating

The product design is rated based on how well the productis designed for ease of disassembly operations. A typicalrating index is the disassemblability index �DI�, which isshown in Equation 7. The RV allow designers to establishhow well the product is designed for disassembly.

DI � Function of �ND;ED;CP ; TD; . . .� �7�

where

ND : number of components disassembled;ED : ease of disassembly;CP : complexity of path;TD : time taken for disassembly.

8.2. Design change recommendations

The design change recommendations, DR allow modi®ca-tion of product at the design stage. The aim of the designrecommendation step is to increase DI. The DI value is usedto suggest possible design changes in the geometric designof the product, material selection and fastener design.For example, Fig. 10 shows a sub-assembly of two

components riveted to each other. At its end of its lifecycle, the disassembly of this product can only be done bydestructive means. Its components cannot be used at theend of its life. One recommendation for this design is tosubstitute riveted joints with screws or snap-®ts in order tomore easily recycle/reuse the component.Design change recommendation rules should be auto-

mated by generating DFD rules such as those found inDFM/DFA rules. (Boothroyd and Alting, 1992). Thegeneration of DFD rules for better product design is beingresearched.

9. Example

This section presents an example illustrating the designmodules involved in the virtual disassembly analysis. Theexample assembly taken for analysis is the heel pad clampassembly (from Earle, 1996), which is shown in Fig. 11.

9.1. Module I. Knowledge base creation

The product DB is analyzed and the product informationR available from the knowledge-base creation module arelisted below:

Fig. 10. Subassembly of a telephone.


(1) The materials (steel, stress proof steel, 1010 CRS,Ledloy and gray iron) need to be separated for recyclingapplication;

(2) The 1010 CRS washer needs frequent replacement;(3) Components C3 and C11 must not be separated while

disassembling;(4) No component should be destroyed;(5) Disassembly path should be geometrically simple;(6) The product contains no hazardous or chemically

reactive material;(7) The components disassembled should be easily ac-

cessible;(8) The heavier component should be clamped;(9) Disassembly cost should be the lowest possible.

The CS is obtained from the product information (1), (2)and (3). The information in (4), (5) and (6) is modeled as Cfor disassembly process. The information in (7), (8) and (9)is modeled as OV. The derived CS;OV and C from R arelisted below:

(1) Component set, CS:

(i) Disassemble all components in a heel pad clampassembly for recycling application;

(ii) Disassemble C7 and C9 for maintenance appli-cations;

(iii)Disassemble C3 and C11 as a subassembly;

(2) Objective variables, OV:

(i) Accessibility of components;(ii) Weight of components;(iii)Cost of disassembly;

(3) Constraints, C:

(i) Destructive disassembly is not allowed;(ii) 1-disassembly should be preferred;(iii)As there are no hazardous components, special

precautions are not required.

9.2. Module II. Disassembly method selection

The disassemblity analysis is performed on the given heelpad clamp assembly (details not shown) and the possibleDMs are listed below:

(1) Recycling application: parallel, monotonic, destruc-tive/non-destructive, complete, 1-m-disassembly;

Fig. 11. Heel pad clamp assembly (from Earle, 1996, p. 381).

Fig. 12. (a) Complete DSo and DPo; (b) Selective DSo and DPo.


(2) Maintenance application: sequential, destructive/non-destructive, monotonic, selective and 1-disassembly.

Once the geometry of the assembly is analyzed and allpossible DMs are obtained the DM that satis®es the userand environmental requirement is selected based on R. Thepreferred DM for both recycling and maintenance appli-cations are listed below;

(1) Recycling application: parallel, monotonic, non-de-structive; indirect, complete, 1-disassembly;

(2) Maintenance application: sequential, monotonic,non-destructive, indirect, selective, 1-disassembly.

9.3. Module III. Disassembly analysis

The OV obtained from the product analysis module isformulated as an OF for each disassembly method. Themetrics for each DM are listed below. For selective disas-sembly the minimum disassembly cost is modeled as min-imizing the number of components disassembled.

(1) OF for complete disassembly:Metric 1: heavier components should be removedlast (RI =0.5);Metric 2: accessibility should be maximumpossible (RI =0.5);

(2) OF for selective disassembly:Metric 1: the number of componentsdisassembled should be minimum (RI =0.7);Metric 2: the weight of the componentdisassembled should be minimum (RI =0.3);

(3) Optimal disassembly sequence and path: The DSofor complete (all components) and selective disassembly(C7 and C9) for heel pad clamp assembly are:

Complete DSo: fC14; C12;C4; C13; C7; C8; C10;C9; C2; C6; fC11; C3g; C5; C1g

Selective DSo : fC13; C7gfC8; C10; C9gFigure 12(a and b) show the complete and selective DSoand DPo. The design of the heel pad clamp assembly (de-sign A) shown in Fig. 13 can then be evaluated for pa-rameters such as disassembly cost and time for theidenti®ed complete DSo and DPo as discussed in Section7.2 (the values are not presented here).

9.4. Module IV. Design analysis

The parameter DI is computed to compare the heel padclamp assembly design with alternatives as discussed inSection 8.1. As an example, four possible alternatives heelpad clamp assembly designs for the highlighted window(Fig. 13) are shown in Fig. 14;

(1) The DI value for design A is better than design B, asC7 in design A can be more easily disassembled (accessi-bility is more) than design B;

(2) To selectively disassemble C7; the DSo for design Ais fC13;C7g. However, in design C, as the joint is perma-

nent, the DSo is fC8;C10;C9;C6;C7g. Hence the DI valuefor design A is higher than design C;

(3) The DI value for design D is better compared todesign A as the number of components that need to bedisassembled to remove C7 is two in design A, but in designD it is only one;

(4) The DI value of design E is better than that of designA as C7 can be disassembled non-monotonically in designE compared to monotonic disassembly in design A. Thisresults in disassembly of C7 without disassembling com-pletely other components. Therefore both the cost of dis-assembly and hence the maintenance is cheap for design E.

Thus design E is preferred for selective disassembly andrated as the better design compared to design A.

10. Discussion

This section presents the main strengths and weakness ofthe proposed DFD framework. An important strength ofthe proposed DFD framework lies in its knowledge-basedapproach, which at every step, prunes the search spaceusing domain-speci®c rules. For example, the DM selectionmodule discussed in Section 6.2 as applied to the car modelassembly (Fig. 7a), prunes down the solutions, case 1(Fig. 7b) and case 2 (Fig. 7c) and selects the appropriateDM (Fig. 7d), which satis®es assembly geometry and R.An alternative would be to list all possible variables andformulate an objective function of all possible variablesand subsequently to optimize this objective function.However, the problem with this approach is that we willnever get an optimal solution in ®nite time (solution will becombinatorial). This shows the advantage of the proposedapproach, which prunes down the search space using rulesat every step (modules). However, it could also be a dis-advantage. The disadvantage is that we may prune out anentire solution set, which could be signi®cantly more op-timal than the solution found. Thus, a tradeo� exists usingknowledge-based approaches.Another important advantage is that our DFD frame-

work provides the best results when the product domain isreasonably ®nite. The pre-existing product DB is for theclass of products of a particular domain (for example,domains like automotive products or a CRT tube). Henceseparate DBs need not be analyzed for individual productsand di�erent product designs of the same domain are an-alyzed with the available DB.

11. Summary

This paper presents a DFD framework consisting of severaldesign modules: (I) knowledge base creation; (II) disassem-bly method selection; (III) disassembly analysis; (IV) designanalysis. The strength of this framework lies in its applica-


Fig. 13. Design A for heel pad clamp assembly.

Fig. 14. Alternative heel pad clamp assembly designs.


bility to a given class of products. Future work should in-clude the analyses of components requiring complex mo-tions for disassembly, optimal disassembly sequencegeneration for di�erent disassembly methods and designchange recommendations based on disassembly ratings.

References

Amezquita, T., Hammond, R., Salazar, M. and Bras, B. (1995)

Characterizing the remanufacturability of engineering sys-tems, in 21st Advances in Design Automation Conference, DE-vol. 82, pp. 271±278.

Ansems, A. M. M., Fugger, E. and Scheidt, L. (1994) Automation

of disassembly process of consumer goods, in IEEE Inter-national Symposium on Electronics and the Environment, pp.343±347.

Beasley, D. and Martin, R. R. (1993) Disassembly sequences forobjects built from unit cubes. CAD Journal, 25(12), 751±761.

Boks, C. B., Kroll, E., Brouwers, W. C. J. and Stevels, A. L. N.

(1996) Disassembly modeling: two applications to a Philips21¢¢ television set, in IEEE International Symposium onElectronics and the Environment, pp. 224±229.

Boothroyd, G. and Alting, L. (1992) Design for assembly anddisassembly. CIRP Annals, 42(2), 625±636.

Bras, B. and Emblemsvag, J. (1995) The use of activity basedcosting, uncertainity and disassembly action charts in

demanufacture cost assemblies, in ASME Design EngineeringTechnical Conference, DE-Vol. 82, Vol. 1, pp. 285±292.

Byrne, P. M. and Deeb, A. (1993) Logistics must meet the green

challenge. Transport and Distribution, February, 33±35.CenCITT, (1995) Environmentally conscious manufacturing; in-

dustrial design for environment via design for disassembly ±

an automotive focus, Center for Clean Industrial andTreatment Technologies (http://es.inel.gov/centers/cencitt/9534.htm).

Chen, R. W., Navin-Chandra, D. and Prinz, F. (1993) Productdesign for recyclability: a cost bene®t analysis model and itsapplication, in IEEE International Symposium on Electronicsand the Environment, pp. 178±183.

Chrysler, (1995) Recycling and conservation. Environmental re-port (http://www.Chrysler.com/environment/recycling.html).

Coulter, S., Bras, B., Winslow, G. and Yester, S. (1996) Designing

for material separation: lessons from automotive recycling, inProceedings of the 1996 ASME DET and CIE Conference, 96-DETC/DFM-1270.

Dutta, D. and Woo, A. C. (1992) Algorithms for multiple disas-sembly and parallel assemblies. ASME Concurrent Engi-neering, PED-59, 257±266.

Earle, J. H. (1996) Graphics for Engineers, AutoCAD Release 13,

Addison-Wesley.Envirolink (1995) Design for disassembly for environmentally

conscious products, (http://www.envirolink.org/issues/disas-

sembly/overview.html).Envirosense (1995a) Newsletter for the nuclear weapons complex.

The Pollution Prevention Advisor, 5(1), also http://es.inel.gov/

new/contacts/newsltrs/pzadv/pzadv.html.Envirosense (1995b) Asset recycling at Xerox (http://es.inel.gov/

techinfo/case/comm/assest-d.html).

Feldmann, K. and Scheller, H. (1994) Disassembly of electronicproducts, in IEEE International Symposium on Electronics

and the Environment, pp. 81±86.Ford (1996) We are learning to disassemble. in Automotive

Recycling (http://www.ford.com/corporat-info/environment/Recycling.htm).

Geiger, D. and Zussmann, E. (1996) Probablistic reactive disas-sembly planning. CIRP Annals, 45(1), 49±52.

Girard, A. and Boothroyd, G. (1995) Design for disassembly.

Report #90, Department of Industrial and ME, University ofRhode Island.

GM (1994) Product life cycle and recycling, in Product Steward-

ship, environmental report (http://www.gm.com/edu_rel/environm/environ3.htm).

GNET (1995) The Netherlands radical, practical green plan. In-

ternational News; Global Network for Environment Technol-ogy (htpp://www.gnet.org/gnet/NEWS/Summary/back_is-sues/1995/NSNOV24.HTM).

Gupta, S. M. and McLean, C. R. (1996) Disassembly of products.

Computers and Industrial Engineering, 31(1±2), 225±228.Halperin, D. (1994) Assembly partitioning with a constant num-

ber of translations. Technical report, Sandia National Labs,

SAND94-1819, pp. 1±17.Harjula, T., Rapoza, B., Knight, W. A. and Boothroyd, G. (1996)

Design for disassembly and the environment. CIRP Annals,

45(1), 109±114.Hoo, S. D., Brezet, H., Curl, M. and Dieleman, H. (1990)

PRISM: Industrial success with pollution prevention, in 2ndEuropean Conference on Technology Assessement, People and

Technology, Italy, pp 27±53.Hrinyak, M. J., Bras, B. and Ho�mann, W. F. (1996) Enhancing

design for disassembly: a benchmark of DFD software tools,

in Proceedings of the ASME DET and CIE Conference, 96-DETC/DFM-1271.

IBM (1996) IBM and the environment; design initiatives and

product advancement, in Product Stewardship, (http://www.ibm.com/ibm/Environmental/annual/06Prod.htm).

IEEE Robotics and Automation Society (1996) Assembly and

task planning technical committee, (http://casper.beckman/uiuc.edu/vr-sharma/tc_atp_home.html).

Ishii, K. (1995) Life-cycle engineering design. ASME Journal ofMechanical Design, 117, 42±47.

Ishii, K. and Lee, B. H. (1996) Reverse ®shbone diagram: a tool inaid of design for product retirement, in Proceedings of theASME DET and CIE Conference, 96-DETC/DFM-1272.

Ishii, K., Lee, B. H. and Eubanks, C. F. (1995) Design for productretirement and modularity based on technology life-cycle, inASME International Mechanical Engineering Congress and

Exposition, Manufacturing Science and Engineering, Vol. 3±2,pp. 921±933.

Johnson, M. R. and Wang, M. H. (1995a), Planning product

disassembly for material recovery. International Journal ofProduction Research, 33(11), 3119±3142, 1995.

Johnson, M. R. and Wang, M. H. (1995b) Product disassemblyanalysis: a cost/bene®t trade o� approach. International

Journal of Environmentally Conscious Design and Manufac-ture, 4(2), 19.

Jovane, F., Alting, L., Armillotta, A., Eversheim, W., Feldmann,

K., Seliger, G. and Roth, N. (1993) A key issue in productlife cycle: disassembly. CIRP Annals, 42(2), 651±658.


Kirby, J. R. and Wadehra, I. (1993) Designing business machinesfor disassembly and recycling, in 1993 IEEE International

Symposium on Electronics and the Environment, pp. 32±36.Kochan, A. (1995) In search of a disassembly factory. Assembly

Automation, 15(4), 16±17.Kroll, E. (1996) Development of a disassembly evaluation tool, in

Proceedings of the ASME DET and CIE Conference, 96-DETC/DTM-1509.

Lapemere, L. and El Maraghy, H. A. (1992) Planning of products

assembly and disassembly. CIRP Annals, 41(1), 5±10.Lee, K. and Gadh, R. (1996) Destructive disassembly to support

virtual prototyping. IIE Journal of Design and Manufactur-

ing, in press.Li, W., Zhang, C., Wang, H. P. B. and Awoniyi, S. A. (1995)

Design for disassembly analysis for ECDM, in ASME In-

ternational Congress and Exposition, Manufacturing Scienceand Engineering, Vol. 2, pp. 969±976.

Lou, S., Leu, J. and Jorjani, S. (1996) Comparing di�erent dis-assembly strategy, in IEEE International Symposium on

Electronics and the Environment, pp. 73±77.Lowe, A. S. and Niku, S. B. (1995) A methodology for design for

disassembly. ASME, Design for Manufacturability, DE-81,

47±53.Mattikalli, R. S. and Khosla, P. (1992) Motion constraints from

contact geometry: representations and analysis, in IEEE In-

ternational Conference on Robotics and Automation, pp.2178±2185.

Motorola (1996) Life cycle solution; Motorola new enterprisesseeking opportunities, in Environmental Interests, (http://

www.mot.com/MNE/env.html).Navin-Chandra, D. (1991) Design for environmentability. DTM

ASME, Design Engineering Division, 31, 119±125.

Navin-Chandra, D. (1993) Restar: A design tool for environ-mental recovery analysis, in 9th ICED, Switzerland, pp. 780±787.

Olsen, W. W. and Sutherland, J. W. (1996) Selection of process tosupport ECM, CenCITT, (http://es.inel.gov/centers/cencitt/9533.htm).

Penev, K. D. and Ron, A. J. (1996) Determination of a disas-sembly strategy. International Journal of Production Re-search, 34(2), 495±506.

Parker, J. E., Boyd, B. L. and Lacy, L. E. (1995) An introduction

to EPA's design for environment program, (http://es.i-nel.gov/dfe/dfeintro.html).

Pohlen, T. L. and Theodore, H. F. M. (1992) Reverse logistics in

plastics recycling. International Journal of Physical Distribu-tion and Logistics Management, 22(7), 35±47.

RHW News (1993) Intelligent Products; News and Resources for

Environmental Justice, no. 360, 21 October (http://www.en-virolink.org/pubs/rachel/rhwn360.htm).

Robotics Resources (1996) UMass Laboratory for Perceptual

Robotics, (http://piglet.cs.umass.edu:4321/robotics.html).Shin, K. and Cho, H. S. (1994) On the generation of robotic

assembly sequences based on separability and assemblymotion stability, in Robotica 94, Vol. 12, pp. 7±15.

Shu, L. H. and Flowers, W. C. (1995) Considering remanufactureand other end-of-life options in selection of fastening andjoining methods, in IEEE International Symposium on Elec-

tronics and the Environment, pp. 75±80.

Shyamsundar, N., Ashai, Z. and Gadh, R. (1996a) Virtual designfor disassembly methodology. Journal of Engineering Design

and Automation, in press.Shyamsundar, N., Srinivasan, H. and Gadh, R. (1996b) Virtual

de-manufacturing via virtual disassembly to design environ-mentally conscious products. International Journal of Envi-

ronmentally Conscious Design and Manufacturing, in press.Siddique, Z. and Rosen, D. (1996) An approach to virtual

prototyping for product disassembly, in Proceedings of the

1996 ASME DET and DIE Conference, 96-DETC/CIE-1345.Spath, D. (1994) The utilization of hypermedia based information

systems for developing recyclable products and for disas-

sembly planning. CIRP Annals, 43(1), 153±156.Spath, D., Hartel, M. and Tritsch, C. (1995) Tools to support

environmental product design and economical disassembly

of technical consumer products, in 10th ICED 95, Praha, pp.1066±1072.

Spicer, A. J. and Wang, M. H. (1995a) A software tool for end oflife cycle consideration within a DSS approach to ECDM.

Computers and Industrial Engineering, 29(1±4), 501±505.Spicer, A. J. and Wang, M. H. (1995b) Optimal disassembly se-

quence generation for complex products: an arti®cial intelli-

gence approach, in Proceedings of the 3rd InternationalCongress on Environmentally Conscious Design and Manu-facturing, Las Cruces.

Srinivasan, H. and Gadh, R. (1997) Virtual selective disassembly:a geometric tool to achieve net positive environmental value,30th ISATA, Florida, Italy, June, accepted.

Srinivasan, H., Shyamsundar, N. and Gadh, R. (1997) A virtual

disassembly tool to support environmentally consciousproduct design, IEEE International Symposium on Electronicsand the Environment, 5±7 May, California, accepted.

Subramani, A. and Dewhurst, P. (1994) Repair time estimationfor early stages of product development. Journal of Designand Manufacturing, 4(2), 129±137.

Suga, T., Saneshige, K. and Fujimoto, J. (1996) Quantitativedisassembly evaluation, in IEEE International Symposium onElectronics and the Environment, pp. 19±24.

SUN (1996) Product stewardship, Corporate Overview, SUNMicrosystems (http://www.sun.com/corporateoverview/ehs/steward.html).

Tani, K. (1995) A concept of a robotic disassembly system for

disused products. International Journal of EnvironmentallyConscious Design and Manufacturing, 4(1), 91±97.

Tani, K. (1996) Some considerations on a robotic disassembly

system for disused products ± in search of the science ofdisassembly, in 1996 Japan/USA Symposium on FlexibleAutomation, ASME, Vol. 2, pp. 815±818.

Thierry, M. C., Salomon, M., Nunen, V. and Wassenhove, L.N. V. (1993) Strategic production and operations manage-ment issues in product recovery management, Management

Report Series, no. 145/1993, Erasmus University, TheNetherlands.

USEPA (1997) Pollution Prevention News, EPA 742-N-97-001,December 1996±January 1997.

Vujosevic, R., Raskar, R., Yetukuri, N. V., Jothishankar, M. C.and Juang, S. H. (1995) Simulation, animation and analysisof design disassembly for maintainability analysis. Interna-

tional Journal of Production Research, 33(11), 2999±3022.


Wang, M. and Johnson, M. (1995) Product disassembly analysis:a case study, in Proceedings of the 3rd International Congress

on Environmentally Conscious Design and Manufacturing,March, Las Cruces, NM.

Weigl, A. (1996) Requirements for robot assisted disassembly ofnot appropriate designed electronic products: lessons from

®rst studies, in Proceedings of the 5th International FAIMConference, pp. 306±316.

Whitney, D. E. (1996) The potential for assembly modeling in

product development and manufacturing. MIT report(http://web.mit.edu/ctpid/www/Whitney/papers.html).

Wilson, R. (1996) Directory of assembly planning research. As-

sembly sequence planning resource directory (http://www.-sandia.gov/2121/archimedes/APing.html).

Wilson, R. H. and Latombe, J. (1994) Geometric reasoning about

mechanical assembly. Arti®cial Intelligence, 71(2), 371±396.Wittenberg, G. (1992) Life after death for consumer products:

designing for disassembling. Assembly Automation, 21(2), 21±25.

Wolter, J. D. (1996) Assembly sequence planning bibliography.Department of CS, Texas A&M (http://www.cs.tamu.edu/research/robotics/wolter/asp/bib.html).

Wolter, J. D., Chakrabarty, S. and Tsao, J. (1995) Mating con-straint languages for assembly sequence planning. IEEETransactions on Robotics and Automation, in press.

Woo, T. C. (1994) Visibility maps and spherical algorithms. CADJournal, 26(1), 6±16.

Woo, T. C. and Dutta, D. (1991) Automatic disassembly andtotal ordering in three dimensions. ASME Journal of Engi-neering for Industry, 113, 207±213.

Xu, Y., Mattikalli, R. and Khosla, P. (1995) Generation of partial

medial axis for disassembly motion planning. Journal ofDesign and Manufacturing, 5(2), 89±102.

Yan, X. and Gu, P. (1995) Assembly/disassembly sequence

planning for life cycle cost estimation, in ASME InternationalMechanical Engineering Congress and Exposition, Manufac-turing Science and Engineering Conference, Vol. 2, pp. 935±

956.Yokota, K. and Brough, D. R. (1992) Assembly/Disassembly

sequence planning. Assembly Automation, 12(3), 31±38.

Zhang, H. C., Kuo, T. and Huang, S. H. (1996) Recycling modelfor end-of-life products, in Japan/USA Symposium on Flex-ible Automation, ASME, Vol. 2, pp. 1127±1130.

Zhang, D., Kuo, T. and Zhang, H. C. (1995) Life cycle engineer-

ing: concepts and researches, in ASME International Me-chanical Engineering Congress and Exposition, ManufacturingScience and Engineering Conference, Vol. 2, pp. 827±841.

Zussmann, E., Kriwet, A. and Seliger, G. (1994) Disassemblyoriented assessement methodology to support design for re-cycling. CIRP Annals, 43(1), 9±14.


a framework for virtual disassembly analysis

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