An Integrated Framework for Supporting Decision Making During Early Design Stages on End-of-Life Product Disassembly

Abstract

Product life cycle (PLC) is the cycle which every product goes through from introduction to eventual demise. There are several issues with the current life cycle of a product when looked from the environmental impact perspective. These are: 1) depletion of natural resources due to the use of virgin materials for production, 2) Consumption of substantial amounts of energy during manufacturing, assembly and use, and 3) production of large amounts of waste during the lifecycle including those at the End of Life (EoL) phase. These issues impact resource scarcity, adverse effects on the environment and loss of embodied energy as waste. Some of the potential solutions to these issues, as proposed in literature, are: to recycle, reuse and remanufacture products in order to reclaim materials, components and sub-assemblies from used products and make them available for new products. In order to efficiently carry out these recovery processes, a pre-requisite is disassembly. Product disassembly is defined as the processes of systematic removal of desirable constitute parts from an assembly while ensuring that there is no impairment of the parts due to the disassembly process. The following are the major research issues in the field of disassembly. One is the conflict between environmental and economic goals, i.e. as to which should be targeted at in disassembly objectives. These conflicts lead to abandoning non-destructive disassembly techniques so as to favour the profit objective. The other issues, prevalent during EoL phase, are: corrosion due to use, less residual value in the parts, complicated structure and intricacy in parts, which together make non-destructive disassembly a task difficult for automation. This means that disassembly processes have to be carried out by human operators. The manual disassembly processes are effort intensive and pose ergonomic risks to the human operators involved in disassembling. The nature of ergonomic risks and effort spent in disassembly is influenced by the efficiency of disassembly operation. However, little research has been carried out to address the above factors of effort, profit, efficiency, environment and ergonomic risk during disassembly in an integrated manner. These factors form the major motivations for the research work carried out in this thesis. A series of empirical studies have been undertaken to assess these factors and their impact on product disassembly. The studies focus on disassembly processes for consumer electronic products in two major recycling sectors in developing countries, leading to development of metrics with which the above factors can be assessed individually and traded off in an integrated manner during the early design stages of a product. These metrics should help designers understand and improve the major disassembly aspects of a product during designing and help prevent major disassembly problems at the EoL phase while improving efficiency of recovery options. The objective of this thesis, therefore, is to develop an Integrated Framework for supporting decision making during early stages of design to improve disassembly during the EoL phase of the product. The framework is intended to help in evaluating alternative designs for easy (less effort), profitable, efficient and environment-friendly disassembly at the EoL phase of the product life cycle. The Framework constitutes new measures developed for supporting decision making on above aspects of disassembly during the early stage of designing. The Framework has been implemented into a computer based tool called ‘IdeAssemble’ and evaluated for its functionality with the help of a design experiment. The tool can be used at the embodiment stage of the design phase, when on an exploded view of the product, with information on its materials, geometry, disassembly tools and types of disassembly task are available to the designer.