Applied Mechanics and Materials Vol. 660 (2014) pp 1067-1071 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.660.1067 A Sustainable Product Realization Strategy using Decomposition-based Approach Lee Guang Benga and Badrul Omarb Faculty of Mechanical And Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. a b [email protected], [email protected] Keywords: axiomatic design, sustainable product realization, design for EOL management, green supplier selection, sustainable manufacturing Abstract. To achieve sustainable product realization, three essential areas namely end-of-line management, green supply chain and sustainable manufacturing have to be considered during the design/development phase. A framework for product realization (presented as objective-mean hierarchy) is proposed in this paper with the help of decomposition-based approach to serve as a guideline for product development companies/firms to improve their environmental strategies by prescribing the key areas and necessary considerations to be scrutinized. Introduction As a result of population growth as well as the improvement of quality of life, more products are being manufactured to offer services or to be consumed directly by users [1]. This complicates environmental sustainability challenge and hence, it is important to minimize environmental footprints associated with these products in order to address environmental issues [2]. Mounting environmental issues, coupled with public pressure and stricter regulations are the main drivers that motivate worldwide firms/companies to change their ways of designing and releasing new products [3]. Firms/companies are being held responsible for producing products in an environmentally friendly way and seamless integration of sustainability into design practices is seen as an area of future importance [2]. Principles of Axiomatic Design and Decomposition of Functional Requirements Axiomatic design (AD) system is a design model based on product attribute in which two axioms are utilized for design. The first axiom highlights the necessity to maintain independence of functional requirements (FR) while the second one is to minimize the information necessary to meet the FRs. In most design tasks, it is crucial to decompose the problem, because the FRs at top levels are abstract and are not substantially detailed for direct realization by means of implementing DPs. Using a structured and consistent method (“zigzagging” between the FRs and DPs) the FRs and DPs at the top level have to be decomposed at a more detailed level in order to develop a feasible design. First, the top level FR is satisfied by a DP. Then, this top level FR (denoted FR1) is decomposed to the next lower level through zigzagging, leading to the definition of two or more subordinate FRs to FR1. For these, corresponding sub-DPs are to be found. The sub-FRs and the sub-DPs operationalize the FR1-DP1 pair. Decomposing is repeated until the appropriate degree of detail is reached, so that the design can be realized at the operational level. The result of the decomposition is a hierarchy of objectives-means: the FR-DP pairs represent the relationships between objectives and means, which are structured and consistently connected across several levels [4]. Sustainable Product Development: The Key Areas End-of-life management is described as a process of converting EOL products into re-marketable products, components, or materials [2] and product design is the most important factor to achieve profitable EOL management [2,5]. In this aspect, additional FRs can be introduced during problem definition stage to differentiate design objectives that address environmental needs from product 1068 Advances in Mechanical, Materials and Manufacturing Engineering FRs that are related to customer needs [6]. Chen proposed a series of FRs and DPs that favor disassembly and recycling [7]. For instance, the author stated that “easier or more economical disassembly of the parts in the product” should be one of the design requirements to fulfill in order to enable product disassembly with less manpower and costs. Other than end-of-life (EOL) management and recycling of products, sustainable product development requires a shared responsibility to implement and realize sustainability throughout the life cycle. The necessary considerations to be taken account during the design stage to attain sustainable product development include downstream issues such as supply chain and manufacturing [2]. Green purchasing can be defined as an environmentally conscious purchasing practice that reduces sources of waste and promotes the recycling and reclamation of purchased materials [8]. It is a boundary-spanning function within the supply chain [9-11]. Min and Galle [12] also stated that incorporating a company’s environmental goals with purchasing activities is essential because purchasing is at the beginning of the green supply chain. Humphreys et al. proposed a list of environmental criteria which are divided into two broad groups i.e. quantitative and qualitative criteria [13]. The pollutant costs (due to treatment of pollutants) and improvement costs (related to improving environmental performance) are grouped under the quantitative category. On the other hand, the criteria identified under the other environmental category grouping are mainly qualitative criteria such as the environmental management system within a company and its green image which require subjective decisions to be made during evaluation of these criteria. Assuming that the buyer is practicing proactive environmental strategy, alternative/candidate should fulfill both quantitative and qualitative criteria at desired level in order to be qualified as green supplier [13]. Machining processes constitute a major manufacturing activity that contributes to the development of the worldwide economy [14]. In the developed world, it is estimated that machining processes contribute about 5% of the total GDP. Furthermore, the importance of machining is anticipated to increase even further due to shorter product cycle and more flexible manufacturing systems induced by economic factors [15]. Due to the above reasoning, machining is chosen to be the focus of discussion in this paper. For easier visualization on the cause-effect relationship, FRs and DPs in Table 1 can be used to represent types of parameters involved in optimization problem (for sustainable machining) and their respective means of fulfilling the requirements. Proposed Sustainable Product Realization Strategy using Decomposition-based Approach Potentially, axiomatic design can be utilized to achieve the aforementioned purpose owing to its advantages stated as follows (1) differentiates between objectives (or requirements) and means (or solutions), (2) allows structured approach to decomposition, making possible step-wise, consistent operationalization and specification of objectives and means, (3) allows cause–effect relationships and objectives-means hierarchies to be systematized, and (4) aids visualization and communication [16]. Fig. 1 shows potential areas that can be tackled by AD principles in order to attain sustainable product development. A sustainable product development framework (see Fig. 2) is proposed by rearranging essential FRs and DPs discussed in the previous section in hierarchical manner. Note that the chart is constructed by using machining as example of major manufacturing process. One should be aware that this framework is applicable to but not limited to products manufactured by means of machining. FRs and DPs being considered in Fig. 2 are listed in Table 2. The top-level requirement for firms/companies to fulfill is to achieve sustainable product development (FR1). This can potentially be attained by considering EOL management, green supply chain and sustainable manufacturing process (DP1). Hence, FR1 is further decomposed to yield FR11, FR12 and FR13 which dictate requirements for the three key areas. Applied Mechanics and Materials Vol. 660 1069 Table 1: FRs and DPs for optimized machining solution. Function Requirements Design Parameters FR1: To maintain cutting condition within manageable range FR2: To attain satisfactory machining performance FR3: To achieve process sustainability at desired level DP1: Parameters of cutting condition must be set within constraints DP2: Employ adequate cooling method DP3: All sustainability factors to satisfy respective requirement Fig. 1: Application of AD into design for EOL management, green supplier selection and optimization for sustainable manufacturing to achieve sustainable product realization. To increase productivity and thus the profit of a product recovery process, the product must be designed to accommodate simple refurbishment process (DP11) and in order to practice green supply chain strategy, parts/raw material must be purchased from green supplier(s) (DP12). Finally, an optimized manufacturing solution is required with the purpose of meeting process sustainability (DP13). FR11 can be strategically decomposed to properly address requirements regarding product function, customer needs and most importantly, requirements that concern product refurbishment (FR111 and FR112). Ideally, all parts should be purchased from green suppliers in order to properly address environmental issues. Therefore, FR12 is further decomposed to specifically impose such requirement on each item (FR121 - FR12N). Then, suppliers of each item should meet the respective quantitative and qualitative environmental criteria (FR1211 and FR1212). Likewise, all parts/components of a product must be manufactured by means of environmentally conscious process so as to maximize the product’s overall sustainability. Consequently, FR13 is decomposed to another level to particularly state requirements related to sustainable process for each part (FR131). As mentioned beforehand, this study uses machining process as illustrative example and should therefore involve requirements related to cutting conditions and machining performance only (FR1311 - FR1313). Other factors (e.g. molding parameters) shall be included should the product calls for additional types of manufacturing techniques. The chart serves as a general guideline for FRs and DPs related to sustainable product development and therefore, the hierarchy can be expanded by further decomposing the FRs to involve more detailed, assembly-specific requirements. By performing the procedure presented in the previous section, with the aid of the set of proposed FR and DP hierarchy, an environmentally friendly product that considers the recovery procedure, green supply chain and sustainable manufacturing can potentially be developed. Conclusion The use of decomposition-based approach to produce a sustainable product development strategy has been the main focus of this paper. The importance of considering design for EOL management, green supplier selection and optimization for sustainable manufacturing has been highlighted in the 1070 Advances in Mechanical, Materials and Manufacturing Engineering FR1 DP1 Design for EOL Management Optimized Sustainable Manufacturing Green Purchasing FR11 FR12 FR13 DP11 DP12 DP13 FR111 FR112 DP111 DP112 FR1111 … FR111N FR1121 … FR112N FR121 DP1111 DP111N DP1121 DP112N DP121 ⁞ ⁞ ⁞ ⁞ … FR12N FR131 DP12N DP131 FR13N … DP13N ⁞ ⁞ FR1211 FR1212 FR1311 FR1312 FR1313 DP1211 DP1212 DP1311 DP1312 DP1313 ⁞ ⁞ ⁞ ⁞ ⁞ Fig. 2: Hierarchy of FRs and DPs to achieve sustainable product development. Table 2: Essential FRs and DPs to achieve sustainable product development. Function Requirements Design Parameters FR1 FR11 FR12 FR13 FR111 FR112 FR121 FR131 FR1111 FR1121 FR1211 FR1212 FR1311 FR1312 FR1313 : To achieve sustainable product development : Functional product that enables effective product recovery : Sustainable supply chain management : Environmentally conscious manufacturing : Media player to have small-sized body and simplistic appearance (example) : Product to have high recovery potential : To purchase raw material for closed-back housing from green supplier (example) : To adopt optimized manufacturing solution for closed-back housing (example) : Closed-back housing to provide protection for internal components (example) : Easier or more economical disassembly of the parts in the product (example) : Supplier(s) to have adequate qualitative environmental capability : Supplier(s) to show satisfactory qualitative environmental capability : Manageable cutting conditions : Satisfactory manufacturing performance : Desired sustainability performance DP1 DP11 DP12 DP13 DP111 DP112 DP121 DP131 DP1111 DP1121 DP1211 DP1212 DP1311 DP1312 DP1313 : To consider EOL management, green supply chain and sustainable manufacturing during design stage : Design for EOL management : Purchase from green supplier(s) : Adopt optimized manufacturing solution : To use closed-back housing with overall dimensions of 50mm×30mm×7mm and button-less control (example) : Fewer parts (or less material volume) in product and more economical replacement of parts in discarded product (example) : Raw material supplier to be assessed based on qualitative and quantitative environmental criteria (example) : Cutting conditions, sustainability and machining performance to be considered during optimization (example) : Maintain substantial housing wall thickness (example) : Defective window to be replaced by minimal recovery operations (example) : Supplier(s) to meet pollutant and improvement costs requirement : Supplier(s) to have acceptable capabilities in terms of management competencies, green image, design for environment, environmental management systems and environmental competencies : Cutting condition to be set within realistic/achievable range : Employ adequate cooling method : All sustainability factors to satisfy respective requirement Applied Mechanics and Materials Vol. 660 1071 content. 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