An Environmentally Conscious EvaluatiodDesign Support Tool for Personal Computers

Hong-Chao Zhang, Steven Yue Yu

Department of Industrial Engineering Texas Tech University

Lubbock, TX 79409-3061

Abstract - The life-cycle of personal computers (PCs) has become shorter in recent years. PC companies are undertaking more pressure to improve the recyclability performance of their new designed PC products. The concept of Design For Environment (DFE) has been adopted by many PC companies to assist their designers to consider the environmental performance of their new PC generation at the early stage of designing. In order to support the requirement of PC companies, this paper develops an environmental evaluation/ design support (WD) tool for PC. The proposed E/D tool is capable of evaluating the new designed PC in terms of environmental sustainability, i.e., material selection, recyclability evaluation, and disassembility analyses.

I. Introduction

Over the last few years, personal computers (PCs) have been rapidly taking the place of traditional computer terminals in main-frame based computer systems. The applications range from office automation to home-based entertainment. The life cycle of the PC has become shorter than ever before. In the meantime, PC companies are undertaking more pressure to improve the recyclability performance of their newly designed computers due to the relative short life span of the PC, the stricter legislative regulation on environmental perspective and stronger environmental conscious from customers’ demand.

Traditionally, a PC has a primary life span of no more than five years before it is considered obsolete, even though its components may not be worn out. A representative of Dell computer Corporation and Aurora Electronics claimed that PCs remain technologically current for roughly six months to one year [7]. The shortening of the PC’s life-cycle has caused an increasing quantity of used PCs being discarded. To solve the environmental problems caused by End-Of-Life products like PCs, legislative authority has established a set of regulations regarding the environment. One of the examples is the establishment and development of IS0 14000, the series of Environmental Management Systems (EMS) standards, which provides a framework to direct the use of organizational resources to the full breadth of actual and potential environmental impacts through reliable management processes and a base of educated and committed employees [5] [g]. PC companies will face much stricter legislative regulation in the near future [6].

On the other hand, traditional product design mainly focuses on fulfilling the functional requirement. Now the

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tendency is paying more attention to environmental performance of the products during the early design stage. Design for Environment (DFE), which comprises several design-related issues (i.e. disassembly, recyclability, health influence, safety impact, and hazard material minimization etc.) is becoming the systematic consideration of design performance with the implementing the products’ functions. However, simultaneously dealing with environmental problems, cost, safety in design is difficult. As the result, the environmental evaluatioddesign support tools are required to implement the DFE ideas in the early stage of product design. The PC industry needs these tools to transform from the traditional idea which focuses on products’ functions to the comprehensive design concept includin8 the environmental aspect.

Now most of PC manufacturers have already agreed that the environmental challenge is one of the central issues for designing a new PC model. They have also accepted the DFE strategy as one of their regular design rules. Apple company has regulated its own DFE strategy and developed the Power Macintosh 7200 emphasizing on enhancing the environmental performance. HP’s “Product Stewards” policy played a significant role in the environmental improvement of HP VECTRA personal computers [9]. IBM has the advanced group to research how to implement IS0 14001 as the long- standing policy commitment to the protection of the environment [8 ] .

This paper reviews the requirement of the software-based design support tools and the current status of the existing tools. Then a design support prototype tool is presented. Compared with other tools, the design support tool is capable of evaluating the new designed PC in terms of environmentally sustainability, i.e., material selection, recyclability evaluation, and disassembility analyses.

11. Overview of current Design Support tools

With the development of DFE theory, the sophisticated design support tools are necessary for the early stage of design. These tools are able to provide guidance on designs regarding to environmental impact, thus assisting designers to integrate environmental conscience into functional considerations [2].

The detail requirements of design support tools are following:

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Functional support: Tools are able to provide reliable database on materials with compliance of environmental regulations, recyclability evaluation and disassembly analyses. Easy-to-catch recommendations: The environmental results generated by D E tools are able to provide a clear prospective on how the current product performs on environmental conscious and how to improve its shortcomings. Standard Compatibility: The common acceptable environmental regulations and policies should be aligned with DFE tools. Merging IS0 14000 standard series is preferred as a highlighted function. Integration: Considering the status of current CAD development, the tools should be integrated with CAD packages. The tools ought to access to CAD databases to retrieve the relevant information such as disassembly data and material information. On the other hand, Environmental Material Inventory (EMI) databases have been developed by more companies. The proposed tools should consider that tendency and offer the interface with the EM1 databases.

Material Assessment

Dozens of tools regarding some aspects of design support, ranging from relatively simple checklists to complex integrated software, have been developed. Some have gained success such as DFMA software developed by Boothroyd Dewhurst Inc [I]. Another example is the D E tool for Printed Wiring Borads developed by Savantage Inc. [lo]. The methods used in these tools include: checklists, design guidelines, matrix functions, and databases of materials.

However, several obstacles hinder design support tools from further developing. One is the lack of reliable data on substitute materials for designing choices. The data from other stages of designing are not comprehensive and accurate for environmental consideration and the EM1 databases in most companies are under developed. Another problem is the lack of the common standard for design support tools. DFE is still in infancy that some terms are not clearly defined for each case, thus it is difficult to evaluate how much the system improves in environmental performance by utilizing DFE tools. A possible solution to overcome these obstacles is to apply a multi-disciplinary policy which requires the engineers from different departments to cooperate with each other in order to develop DFE tools 121.

Recyclability Disassembly Evaluation Analyses

111. A design support tool for Personal Computers

An environmental evaluatioddesign support (Em) tool is presented in this paper, especially for supporting early designing stage of Personal Computers. The proposed E D tool is a window-based decision making and database management software. It can provide checklists, guidelines,

I

Fig. 1 System Architecture.

graphs, and tables based on the EM1 database. The main functions include (Fig. 1):

Material assessment and suggestion;

Disassembility analyses; EM1 database connection;

Recyclability evaluation and hazard material index;

The overall assessment of a PC model which is obtained by using multiattribute factor method.

Of the five functions of the software, EM1 database connection function is the data source of the other functions. The overall assessment of a PC model is established by retrieving four indices from Material Assessment and Suggestion function, Recyclability evaluation and hazard material index function, and Disassembility analyses function.

Overall assessment of a PC model

Fig. 2 Overall Assessment.

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By providing the overall assessment, the E/D tool can present PC designers a clear prospective on how the environmental factors affect their new product design (Fig. 2). The indices which are calculated by three functions, have been normalized a uniform format in order to compare different stages of PC models easily. Four indices, which include material assessment, hazard material counting, recyclability evaluation and disassembility analyses, follow the LowerBetter criterion. The criterion means the lower score standing for the less environmental impact, thus performing better in the environmental aspect. By decreasing these scores compared with the original design, PC designers can make their new products more environment-friendly. Because it is difficult to regulate a standard for DFE, the function use the percentage comparison between the original model and the update model.

Another highlight that the Overall assessment function provides -is the comparison of two different models, which can provide designers the track from the current model to old models. The designers can check the progress of the new model on environmental performance and determine which aspect they should improve further.

selection will output the best environmental score. The position of each arrow end is obtained by answering

the different questionnaires including checklists, listboxes and multichoices concerned about material selections, which are connected with the EM1 database. The questionnaire function can withdraw the relevant scores from the EM1 database according to the different answers, then assign the factors to different kinds of questions. The factors and scores are included into a matrix which helps to obtain the final assessment. Moreover, the computerized questionnaires can not only provide the assessment from users’ choices, but give some useful suggestions according to different answers as well (Fig. 4). The position of each arrow end in material target is calculated using following equation:

n

i = I x= c w i x s i

.In the above equation, X stands for the total score for each module in material selection. Wi is the weight factor for each question which is obtained from the user defined matrix. Si stands for the score retrieved from the EM1 database

Material Assessment/Suzgestion

Material AssessmenVSuggestion function, based on the EM1 database, uses the Target Technique to grade the existed materials of each module in personal computers, then provides the suggestions of recommending materials, and evaluates the material compatibility, etc. The Target Technique is presented in Fig. 3. In the figure, each arrow end rcpresents the environmental impact of materials in cach module. Obviously, the nearer to center for each arrow end, the bctter performance regarding to material assessment for the new PC model. By reshooting each arrow on the material target, PC designers may determine which kind of material

Fig. 4 Questionnaires on line.

according to different answers of each question. The material assessment function also provides the on-line

construction function, which allows users to establish their own questionnaires. After establishing the user-defined qucstions, designers can evaluate their new products by using these criteria immediately. Therefore, the software is more flexible for various requirements.

Recvclability Evaluation

Fig. 3 Target Technique.

Typically six retiring methods are needed to recycle the out-of-date products. These methods include: reusing, remanufacturing, recycling to high grade material, recycling to low grade material, incinerating for energy content and

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\ Dump in landfill site / Incinerate energy content

Recycle in l ow grade

Remanufacture

Fig. 5 Retiring hierarchy.

discarding. The retiring hierarchy is presented in fig. 5. The function categorizes the modules/parts of a computer into these methods and assigns each method a weight factor. By establishing the recyclability tables of the EM1 database, different parts are assigned to the different scores in one module. After calculating the whole score, the function can provide designers a clear result on how their product performs in the recyclability aspect. By using the graph, designers can also determine which module contributes the most recycling obstacle, thus they will focus on this module to improve the recyclability performance of the whole product.

Today many companies and associations have established their own Hazard Material (HM) Database for environmental evaluation. To keep this pace, the hazard material table in the EM1 database connection is also constructed. Based on this table, the function can calculate the total number of hazard materials in the whole product and indicate the module which has a significant contribution on hazard materials.

The developed function is shown in Fig. 6. In the figure,

Fig. 6 Recyclability evaluation.

there are twelve components in one computer model. Each component has the recyclability index and the hazard material sum shown below its icon. The total recyclability index and the hazard material number are displayed above twelve icons. To improve the recyclability performance of each component, designers can click the icon and enter into the EM1 database connection function to retrieve the substitute material. The hazard material sum will change automatically according to the different material selection.

Disassembility Analvses

Disassembly relationship is a key factor in environmental evaluation. The disassembility analyses function focusing

Fig. 7 Disassembly table.

various fasteners, provides designers a cross-table

on

to represent the disassembly information of every two modules. In the table, each module occupies in both row 1 and column 1; other columns and rows stand for the assembly information. The different colors in the table mean different disassemble relationships between every two modules and the numbers 1-9 stand for the difficulty degree of disassembly. The higher score, the more difficult to be disassembled (Fig. 7).

Further disassembly explanation is presented by clicking any tabulate. Changing the disassembly relationship of every two modules on line is also available for designers to improve disassembility performance of their new designed PC model. The whole disassembly assessment score is obtained by summing the disassemble score of every two modules. The lower score stands for the better disassembility performance for the whole product. This function also provides graphs to represent the scores clearly.

The disassembly relationship information may be retrieved from the CAD assembly tree, thus all disassembly information can be integrated with CAD database. Actually most CAD

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Fig. 8 Typical assembly tree.

software companies offer standard design exchange files such as IGES, STEP, DXF files. Therefore it is possible to retrieve the necessary disassembly data from these standard files, then translate them into the assembly tree for the disassembly assessment. The typical assembly tree is shown in Fig. 8. From the figure, two types of symbols, including nodes and edges, are summarized if the tree is regarded as a graph. The node represents a component or a sub-assembly in the physical design and the edge contains the relation information between two nodes.

To retrieve data from the CAD software, it is necessary to translate the graph into the mathematics representation as follow:

A =

N I 0 .. .. 0 .. .. 0 .. 0

Eil .. Ni .. 0 .. . . . . . . 0

Enl .. Eni .. N,,

The matrix A contains the information of both nodes and edges. Ni (i=l, ..., n) represents the information of the ith

node. Eij (i=l ... n, j= l ... n, i#j) represents the assemble

relations between the ith node and the jth node. The simplest method to determine if two nodes are

connected is: [ 1 if i , j linked

E.. = ’ \O if i, j unlinked

However, there are more information hidden in edges and nodes, e.g. fastener information, disassembly cost, etc. Therefore three classes are constructed to detail Ni and Eg .

Class Node

Public:

private:

I

Integer NodeID;

String NodeName; //Node name String NodeMaterial; //Node material String NodeRecycleMode;//Recycling mode Real NodeRecycleCost; //Recycling cost Vol NodeVolumn; /me volume of the bound

Real Nodeweight; //The weight of the node Real NodeLandfillCost; //The landfill Cost Boolean Interference[6]; //The interference mode of

//the node in +X,-X,+Y,-Y,+Z,-Z Boolean Interference(); //The function to calculate

//the interference result between this node //and other //nodes, return a Boolean

//The index of the node

//box which is the least box include the node

1

Class Link I

Integer LinkID; //The index of a link Integer FastenerNumber; //Number of fasteners Integer FastenerID[FasternerNumber];

//The indexes of fasteners 1

Class Fastener (

Integer FastenerID; //Fasterner index String FastenerName; //Fastener name String DisassemblyMethod; //Disassemble method String DisassemblyTool; //Disassemble tool Real DisassemblyTime; //Disassemble time

1

After constructing three disassembly classes, it is easy to retrieve the relevant information from the CAD database. If the CAD package cannot provide some environmental data, the class information retrieving from the EM1 database or inputting by manual should be considered.

EMI database connection

Material, recycling and disassembly related information should be stored in a unique EM1 database. It is important to establish the connection between the design support tool and EM1 database. By utilizing the “Datapipe” technology, the

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tool is able to access most compatible databases (Fig. 9). The DataPipe technology is the function provided by some front end database tools to retrieve different types of tables from different databases. Based on the common data platform, the design support tool can extract the environmental information from the different types of the EM1 databases.

Microsoft Access, SQL Sybase, Oracle

Dbase, lnformix ...

3 EM1 Database

Material v Recyclabiltiy

Disassembly

Fig. 9 EM1 database connection.

The integration with CAD packages is considered by extracting the geometry and assemble information from the CAD database.

IV. Conclusion

The paper focused on proposing a PC design support prototype model based on the EM1 database. It is proved to help PC designers considering more environmental impact of the new designed personal computers, and thus can provide more “green” computers to the market. If the database is modified, it can be applicable for other electrical equipment on environmental evaluation.

Nonetheless, the research on design support is in its infancy. Further development both on DFE theory and EM1 database will bring more mature design support tool to improve environmental performance for PCs.

Acknowledgment

This research was supported by Texas Higher Education Foundation under Advanced Technology Program (ATP) #063644-130.

References

[ l ] Geoffrey Boothroyd, et al. Product Design for Manufacture and Assembly, Marcel dekker Inc. 1994 [2] C. Mizuki, P.A. Sandbom, G. Pitts, “Design for Environment - A survey of Current Practices and Tools”, 1996 IEEE International Symposium on Electronics & the Environment, pp. 1-6 [3] Hong C. Zhang, Tsai-Chi Kuo, “Disassembly Model for Recycling- Personal Computer”, Technical Paper, SME 1996 [4] T. A. Hanft, E. Kroll, “Ease-of-Disassembly Evaluation in Design for Recycling”, Design for X : Concurrent Engineering Imperatives, ed. G.Q. Huang, Chapman & Hall, 1995 [5] M. Blazek, B. Dambach, “Integrating fS0 14000 Environmental Management Systems and Design for Environment at AT&T”, 1996 IEEE International Symposium on Electronics & the Environment, pp. 255-259 [6] Brian Rothery, IS014000 and IS09000, Gower Publishing Limited, 1995 [7] G. Mauro, 1995, “Computer Recycling : In Layman’s Term, Texas General Land Office [8] G. Woodside, B. Blam, S . Payne, “Implementing IS0 14001: A Case Study”, 1996 IEEE International Symposium on Electronics & the Environment, pp. 248-254 [9] Tom Korpalski, “The role of the ‘Product Steward’ in Advancing Design for Environment in Hewlett-Packard’s Computer Products Organization”, 1996 IEEE International Symposium on Electronics & the Environment, pp. 37-41 [lo] P. Sandbom, G. McFall, “Performing Design for Environment Concurrent with Interdisciplinary Tradeoff Analysis of Electronic Systems”, 1996 IEEE International Symposium on Electronics & the Environment, pp. 167-172

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