This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

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Metal Additive Manufacturing: A Review

Thirty years into its development, additive manufacturing has become a mainstream manufacturing process. Additive manufacturing build up parts by adding materials one layer at a time based on a computerized 3D solid model. It does not require the use of fixtures, cutting tools, coolants, and other auxiliary resources. It allows design optimization and the producing of customized parts on-demand. Its advantages over conventional manufacturing have captivated the imagination of the public, reflected in recent mainstream publications that call additive manufacturing “the third industrial revolution.” This paper reviews the societal impact of additive manufacturing from a technical perspective. Abundance of evidences were found to support the promises of additive manufacturing in the following areas: (1) customized healthcare products to improve population health and quality of life, (2) reduced environmental impact for manufacturing sustainability, and (3) simplified supply chain to increase efficiency and responsiveness in demand fulfillment. In the mean time, the review also identified the need for further research in the areas of life-cycle energy consumption evaluation and potential occupation hazard assessment for additive manufacturing.

Additive manufacturing and its societal impact: a literature review

Environmentally conscious manufacturing and product recovery (ECMPRO): A review of the state of the art

Sustainability assessment is being increasingly viewed as an important tool to aid in the shift towards sustainability. However, this is a new and evolving concept and there remain very few examples of effective sustainability assessment processes implemented anywhere in the world. Sustainability assessment is often described as a process by which the implications of an initiative on sustainability are evaluated, where the initiative can be a proposed or existing policy, plan, programme, project, piece of legislation, or a current practice or activity. However, this generic definition covers a broad range of different processes, many of which have been described in the literature as 'sustainability assessment'. This article seeks to provide some clarification by reflecting on the different approaches described in the literature as being forms of sustainability assessment, and evaluating them in terms of their potential contributions to sustainability. Many of these are actually examples of 'integrated assessment', derived from environmental impact assessment (EIA) and strategic environmental assessment (SEA), but which have been extended to incorporate social and economic considerations as well as environmental ones, reflecting a 'triple bottom line' (TBL) approach to sustainability. These integrated assessment processes typically either seek to minimise 'unsustainability', or to achieve TBL objectives. Both aims may, or may not, result in sustainable practice. We present an alternative conception of sustainability assessment, with the more ambitious aim of seeking to determine whether or not an initiative is actually sustainable. We term such processes 'assessment for sustainability'. 'Assessment for sustainability' firstly requires that the concept of sustainability be well-defined. The article compares TBL approaches and principles-based approaches to developing such sustainability criteria, concluding that the latter are more appropriate, since they avoid many of the inherent limitations of the triple-bottom-line as a conception of sustainability.

Conceptualising sustainability assessment

Design of sustainable supply chains under the emission trading scheme

Disassembly modeling, planning, and application

Design methods for sequence controllers play a very important role in advancing industrial automation. The increasing complexity and varying needs of modern discrete manufacturing systems have challenged the traditional design methods such as the use of ladder logic diagrams (LLDs) for programmable logic controllers. The methodologies based on research results in computer science have recently received growing attention by academic researchers and industrial engineers in order to design flexible, reusable, and maintainable control software. Particularly, Petri nets are emerging as a very important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems. This paper identifies certain criteria to compare LLDs and Petri nets in designing sequence controllers and responding to the changing control requirements. The comparison is performed through a practical system after introducing "real-time Petri nets" for discrete-event control purposes. The results reported in this paper will help: (a) further establish Petri net based techniques for discrete-event control of industrial automated systems; and (b) effectively convince industrial practitioners and researchers that it is worthy and timely to consider and promote the applications of Petri nets to their particular discrete-event control problems. >

Comparing ladder logic diagrams and Petri nets for sequence controller design through a discrete manufacturing system

This paper presents a method for analyzing the environmental performance of solid freeform fabrication (SFF) processes. In this method, each process is divided into life phases. Environmental effects of every process phase are then analyzed and evaluated based on the environmental and resource management data. These effects are combined to obtain the environmental performance of the process. The analysis of the environmental performance of SFF processes considers the characteristics of SFF technology, includes material, energy consumption, processes wastes, and disposal. Case studies for three typical SFF processes: stereolithography (SL); selective laser sintering (SLS); and fused deposition modeling (FDM) are presented to illustrate this method.

Environmental performance analysis of solid freedom fabrication processes

Industrial demanufacturing is a practice of growing importance due to increasing environmental and economic pressures. However, very little research focuses on it from a system perspective. This paper presents a disassembly planning and demanufacturing scheduling method for an integrated flexible demanufacturing system. Workstation Petri net and Product Petri net are proposed for its hierarchical and modular modeling in order to derive the disassembly path with the maximal end-of-life value. Scheduling Petri net is introduced to schedule the demanufacturing resources. The proposed methodology and algorithms are demonstrated through the disassembly of personal computers in an integrated flexible demanufacturing system.

An integrated approach to disassembly planning and demanufacturing operation

This paper presents a mathematically sound model for the design and optimization of supply chains in terms of such important performance indexes as product cost, cycle time, quality, energy and environmental impact in the context of global and Internet-based manufacturing. The two layer model is a hyper-network of material flows overlaid with an e-business information network. It extends from a traditional supply chain having suppliers, distributors, and users to include end-of-life product collectors and de-manufacturers. Furthermore, it extends the performance considerations from cost and productivity to include environmental performance. Such extensions allow one to develop Internet-based manufacturing systems that are agile and can produce desired products with the minimum environmental impact over their life cycles. Fuzzy logic-based optimization goals are used in the proposed multiobjective optimization model. A personal computer containing such mechatronic components as hard disk driver, keyboard, and mouse is used as an example to illustrate the application of the proposed integrated e-supply chain model.

Reggie J. Caudill

Papers

Disassembly modeling, planning, and application

Comparing ladder logic diagrams and Petri nets for sequence controller design through a discrete manufacturing system

Environmental performance analysis of solid freedom fabrication processes

An integrated approach to disassembly planning and demanufacturing operation

An integrated e-supply chain model for agile and environmentally conscious manufacturing