Design for Disassembly Tracy Dowie-Bhamra Designing products in order to minimise their impact on the environment is becoming increasingly important. Many designers are beginning to recognise this fact and are therefore demanding tools and techniques which enable them to design more responsibly. One technique which can be used is Design for Disassembly - this enables the product and its parts to be easily reused, re-manufactured or recycled at end of life. This paper not only presents this technique but also illustrates its use with a case study. It is hoped that this will encourage designers to consider product disassembly early in the product's design stage. Introduction In the past two decades environmental concern has focused on production processes, and environmental regulation has concentrated on pollution from industry. However, there is growing awareness that this may not be sufficient and it is increasingly recognised that the use and disposal phases, as well as the production phase of the product life cycle, are important. Environmental regulation and consumer pressure are forcing manufacturers to become more responsible for the safe disposal and recycling of used products. This requires a new approach to product design, one which results in a product designed for all the stages of its life-cycle. Traditionally issues considered in design have related only to function, appearance and financial concerns. As the decisions made by designers have a direct effect on the amount of raw material used, the amount of energy consumed and pollution produced by a product during its lifetime it is important that designers are given the right information and tools to enable them to minimise the effect their products will have on the environment. This is where the discipline of Design for the Environment (DFE) has an important role to play. In recent years the information on Design for the Environment has greatly increased allowing designers to gain some understanding of the subject. Fiksel 1 has defines Design for the Environment (DFE) as a systematic consideration of design issues related to environmental and human health over the life cycle of the product. Hill 2 identified eight aspects which should be included in design for the environment:
These eight aspects can involve lengthy analysis of the design and may therefore deter many from considering using such a technique. Design for the Environment can therefore be divided into three parameters for design 3:
Process design focuses on the reduction of energy consumption and the minimisation of wastes and pollution processes. Material design is concerned with the selection and use of raw materials to minimise; hazardous wastes, amount and type of pollution emitted, and total amount of materials required. Energy consumption design is the selection of materials and processes which result in a reduction of the product's energy requirement when been manufactured or used. Design for the environment Many companies are introducing the Design for the Environment principles into their product designs. For example AT&T 4 began introducing these principles into engineering design but limiting the scope of their application. Initially only the impacts associated with product manufacture and disposal were addressed. The other issues will be addressed as the company's knowledge base expands. IBM began undertaking a programme of Design for the Environment (DFE) in 1989. The designers were asked to consider DFE characteristics along with traditional criteria such as cost, quality and performance 5. Design for the Environment encompasses many issues including Design for Disassembly and Design for Recycling. The importance of Designing for Disassembly became apparent as recovering parts and materials from end-of-life products increased in popularity. There are a number of benefits of achieving efficient disassembly of products as opposed to recycling a product by shredding, which include 6:
Although most products can be disassembled eventually, lengthy disassembly does not make for economic recycling as the cost of disassembly is likely to be much larger than the revenue gained through recycling the parts and materials from the product. It is for this reason that designing products for easy disassembly has increased in popularity enabling more of the product to be recycled economically. Research into design for disassembly Research into Design for Disassembly is taking place at many Universities and companies throughout Europe, Scandinavia and North America. Many of these institutions have produced work suggesting ways in which Design for Disassembly should take place. Jovane et al 7 in a review of research into Design for Disassembly identified thirteen research groups who were active in this area. Kahmeyer and Leicht 8, at the Fraunhofer Institute in Germany (FhG) highlight disassembly as an area for examination in light of impending waste disposal legislation which would encourage the 'take back' of products by the original equipment manufacturer (OEM). This work has been contributing to a change in thinking in some design departments in Germany by presenting designers with design rules which are listed in order of preference. This has been developed into a methodological approach at the FhG to be used to assess the potential ease of disassembly of products 9. Beardsley et al 10 have approached the disassembly problem from a design for assembly point of view, conducting similar analysis of products to analyse their theoretical minimum number of parts before redesign takes place. There are other research groups also looking at Design for Disassembly by taking the DFA approach at the University of Rhode Island 11,12 and also at Ohio State University 13. At Carnegie-Mellon University a great deal of work has been undertaken to address the problem of 'designing for recycling'. They have proposed two approaches for designing for recycling 14, one involves a 'cost benefit analysis model' of recycling, the other encourages designers to design for disassembly by supplying them with two sets of design rules. These rules are concerned with material selection and ease of disassembly. The most comprehensive work on Design for Disassembly has been carried out by Beitz 15 and VDI 16 who have identified the more detailed areas associated with Design for Recycling, these are:
Beitz argues that when a product reaches the end of its life it should be dealt with in such a way that much of it could be used again in some form. Designing using all of the above methods would ensure that the product could be reused to its full potential. From the list above it can be seen that disassembly plays an important role not only in enabling parts and materials to be removed for recycling but also enabling reconditioning, refurbishment, re-manufacture, repair and service of the product and components extending their useful life. This brief review has shown that whilst the information on Design for the Environment, Recycling, Refurbishment and Re-manufacture is becoming more widely available to designers there is one issue which is central to all these principles, Design for Disassembly. The hierarchy of the 3R's , Reuse, Re-manufacture (or Refurbishment) and Recycling, is one which is now recognised as one which should be followed when ever possible and illustrates just how important ease of disassembly is. Figure 01 below shows that there are actually two levels of the 3R's, product level and part level. Principles of design for disassembly Throughout the research into product design for disassembly I believed that one of the easiest way to give information on new design principles to designers was in the form of design guidelines. These can be used in two ways, firstly full training using the guidelines and case study material enables designers to understand why particular guidelines are needed, and secondly giving each designer access to the guidelines whilst they are designing enables them to apply the principles whenever possible. The guidelines I have developed are concerned with disassembly for recycling but can be used (with the addition of extra guidelines) for disassembly for re-manufacture or reuse. They are divided into three categories which are related to the three important areas of disassembly and recycling, these are:
Table 1 in the previous column presents all the proposed designers guidelines. Analysis of a variety of existing products has taken place using these guidelines enabling redesign suggestions to be made to improve their disassembly and recycling performance. Some of these will now be discussed to illustrate the guidelines, however, a full discussion and explanation of each guideline is given by Dowie 17. Redesign of a telephone The following case study illustrates only one of the many products examined using the guidelines. Further illustrations can be found in numerous technical reports published by Manchester Metropolitan University 18, 19, 20, 21 all of these illustrate products which are typical of those which may have to be recycled in the future as they are contain, plastic casings containing wiring, circuit boards, electric motors and similar parts. In order to assess these a product it is necessary to either, disassemble a product to examine each part or, study the original designs to identify those areas where improvements could be made. Often these areas do not become clear until the potential disassembly time has been calculated, this can be done by estimating the time taken for each stage of the disassembly 22. The telephone, shown in Figure 02 below is a mixture of a number of different materials but does have substantial quantities of ABS which can be recycled. As the figure shows there are a number of small parts which must be removed if the ABS casings are to recovered uncontaminated for recycling. The base casing contains four incompatible feet which are slow to remove and are therefore an ideal candidate for redesign. Unfortunately, due to anti-slip regulations, it is necessary to have another material on the base to prevent the telephone slipping and therefore this feature cannot be eliminated completely. However, it was realised that the telephone already had parts of another material protruding from the base casing, these are the line cord and the handset cord which are coated in PVC. Through redesign of the moulding it was felt that these parts could easily replace the need for additional feet, this is illustrated in Figure 03 over the page. Other areas of the phone which were targeted as candidates for redesign were the ringer and the number of screws. The ringer is currently a separate part which is attached to the base casings and connected to the circuit board via a wire and can often be awkward to remove. One idea for design is to combine the ringer with the PCB thus eliminating the need for a separate part and additional wires, this is fully illustrated in Figure 04 below. The number of screws tends to be a problem with many products - screws are often slow to disassemble. Therefore the number of screws used to attach the top and base casings of the telephone were ideal candidates for redesign. A good way to reduce the number of screws is to replace two of them with retaining lugs, as illustrated in Figure 04 below, which would make disassembly much quicker and easier. The telephone case study illustrates that many of the designer's guidelines can be regarded as 'common sense' and easy to apply. By re-educating designers to consider all these issues products can be designed which are easy to disassembly and therefore enable parts and materials to be reused, re-manufactured or recycled. However, it is important to note that before the designers can begin to design a product it is essential that they are aware of the intended route for the product when it reaches its 'end of life'; that is, whether the product and its parts will be reused, refurbished, re-manufactured, recycled or incinerated. Designing for these different end of life options requires the consideration of different design criteria for each. Therefore it is extremely difficult to design a product which would meet all of the criteria for all possible end of life options. It is also important to note that it is very difficult to design a product which will perform well at end of life if only general environmental criteria have been followed at the design stage. Therefore the specific guidelines presented here can only be used for designing for disassembly and recycling, and additional ones should be added for reuse or re-manufacture. In recent years there is one underlying factor which has become apparent, recycling of electronic and electrical goods is currently a very marginal (in terms of resulting profit) activity but one which needs to be encouraged more in the future. For this to happen it is important to ensure that products are designed in a way so as attractive as possible to recyclers. There is one way which will ensure that products will be recycled in greater quantities in the future, and that is to make products very quick and easy to disassemble. Of course, products should also be made from recyclable material. However, they will only be recycled if they can be disassembled and sorted very quickly. Because the majority of materials have a relatively small recycling value it is important that the disassembly cost is even smaller. This will mean that there is a positive profit after disassembly and this can only happen if disassembly is quick and easy. References 1)Fiksel
J., (1993) Design
for the Environment: An integrated systems approach, IEEE
International Symposium on Electronics and the
Environment, Virginia, IEEE. 2)Hill
B., (1993)
Industry's integration of environmental product design,
IEEE International Symposium on Electronics and the
Environment, Virginia, IEEE. 3)Wang
M. H., Johnston M.R. and Dutta S., (1993) Design for the Environment: An
imperative concept in concurrent engineering, CE &
CALS, Washington. 4)Glantschnig
W. J., (1993) Green
Design: A review of issues and challenges, IEEE
International Symposium on Electronics and the
Environment, Virginia, IEEE. 5)Ashley
S., (March 1993)
Designing for the environment, Mechanical Engineering,
52. 6)Wittenberg
G., (1992) Life
after death for consumer products, Assembly Automation,
12(2). 7)Jovane
F., Alting L., Armillotta A., Eversheim W., Feldmann K.,
Seliger G. and Roth N., (1993) A key issue in product life cycle:
disassembly, Annals of the CIRP 42(2). 8)Kahmeyer
M. and Leicht T. (1991) Dismantling facilitated, Kunststoffe German
Plastics 81(12). 9)Schmaus
T. and M. Kahmeyer (1992) Design for disassembly - challenge of the
future, DFMA 1992, RI, USA, BDI. 10)Beardsley
B., Parulian A., Berners D. and Kroll E. (1993) Product evaluation for ease of
disassembly, Texas A & M University. 11)Boothroyd
G. and Alting L. (1992) Design for assembly and disassembly, Annals
of CIRP, 41(2). 12)Dewhurst
P. (1993) Design
for disassembly, Boothroyd Dewhurst Inc.. 13)Burke
D.S., Beiter K. and Ishii K. (1992) Life-cycle design for
recyclability, Design Theory & Methodology, 42. 14)Chen,
R. W., Navin-Chandra D. and Prinz F. (1993) Product Design for recyclability: A
cost benefit analysis model and its application, IEEE
International Symposium on Electronics & the
Environment., Virginia, IEEE. 15)Beitz
W. (1993)
Designing for ease of recycling, Journal of Engineering
Design, 4(1). 16)VDI 2243, Konstruieren recyclingerechter technischer
produkte, Dusseldorf, VDI, 1991. 17)Dowie
T. (1995) A
disassembly and optimisation methodology for design, PhD
Thesis, Manchester Metropolitan University. 18)Dowie
T. and Simon M. (Nov 1993) Disassembly
and recycling analysis of telephones, Technical Report
DDR/TR9, Manchester Metropolitan University. 19)Dowie
T. and Simon M. (Jan 1994) Disassembly and recycling analysis of a
vacuum cleaner, Technical Report DDR/TR10, Manchester
Metropolitan University. 20)Dowie
T. and Simon M. (Mar 1994) Disassembly and recycling analysis
of a cylinder vacuum cleaner, Technical Report DDR/TR11,
Manchester Metropolitan University. 21)Dowie
T. (Jan 1995)
Disassembly and recycling comparison of a Hoover
Turbopower 1000 and Electrolux Z1490, Technical Report
DDR/TR20, Manchester Metropolitan University. 22)Dowie
T. (Oct 1994)
Estimation of disassembly times, Technical Report
DDR/TR15, Manchester Metropolitan University.
|
