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Additive manufacturing (AM) technologies, such as selective laser sintering (SLS) and fused deposition modeling (FDM), have become the powerful tools for direct manufacturing of complex parts. This breakthrough in manufacturing technology makes the fabrication of new geometrical features and multiple materials possible. Past researches on designs and design methods often focused on how to obtain desired functional performance of the structures or parts, specific manufacturing capabilities as well as manufacturing constraints of AM were neglected. However, the inherent constraints in AM processes should be taken into account in design process. In this paper, the enclosed voids, one type of manufacturing constraints of AM, are investigated. In mathematics, enclosed voids restriction expressed as the solid structure is simplyconnected. We propose an equivalent description of simply-connected constraint for avoiding enclosed voids in structures, named as virtual temperature method (VTM). In this method, suppose that the voids in structure are filled with a virtual heating material with high heat conductivity and solid areas are filled with another virtual material with low heat conductivity. Once the enclosed voids exist in structure, the maximum temperature value of structure will be very high. Based upon this method, the simplyconnected constraint is equivalent to maximum temperature constraint. And this method can be easily used to formulate the simply-connected constraint in topology optimization. The effectiveness of this description method is illustrated by several examples. Based upon topology optimization, an example of 3D cantilever beam is used to illustrate the trade-off between manufacturability and functionality. Moreover, the three optimized structures are fabricated by FDM technology to indicate further the necessity of considering the simply-connected constraint in design phase for AM.

Laser Powder Bed Fusion (LPBF) brings the possibility to manufacture innovative near-net-shape part designs. But unfortunately, some designed surfaces suffer from rough surface finish due to characteristics of the LPBF process. This paper explores trends in managing surface roughness and through a space industry case study, a proposed process that uses Additive Manufacturing Design Artefacts (AMDAs) is used to investigate the relationship between design, surface roughness and fatigue. The process enables the identification of design uncertainties, however, iterations of AMDA's can be required.

Purpose This paper aims to review recent research in design for additive manufacturing (DfAM), including additive manufacturing (AM) terminology, trends, methods, classification of DfAM methods and software. The focus is on the design engineer’s role in the DfAM process and includes which design methods and tools exist to aid the design process. This includes methods, guidelines and software to achieve design optimization and in further steps to increase the level of design automation for metal AM techniques. The research has a special interest in structural optimization and the coupling between topology optimization and AM. Design/methodology/approach The method used in the review consists of six rounds in which literature was sequentially collected, sorted and removed. Full presentation of the method used could be found in the paper. Findings Existing DfAM research has been divided into three main groups – component, part and process design – and based on the review of existing DfAM methods, a proposal for a DfAM process has been compiled. Design support suitable for use by design engineers is linked to each step in the compiled DfAM process. Finally, the review suggests a possible new DfAM process that allows a higher degree of design automation than today’s process. Furthermore, research areas that need to be further developed to achieve this framework are pointed out. Originality/value The review maps existing research in design for additive manufacturing and compiles a proposed design method. For each step in the proposed method, existing methods and software are coupled. This type of overall methodology with connecting methods and software did not exist before. The work also contributes with a discussion regarding future design process and automation.

The last few decades have seen rapid growth in additive manufacturing (AM) technologies. AM has implemented a novel method of production in design, manufacture, and delivery to end-users. Accordingly, AM technologies have given great flexibility in design for building complex components, highly customized products, effective waste minimization, high material variety, and sustainable products. This review paper addresses the evolution of engineering design to take advantage of the opportunities provided by AM and its applications. It discusses issues related to the design of cellular and support structures, build orientation, part consolidation and assembly, materials, part complexity, and product sustainability.

This paper reports the study and development case of an innovative application of the Cloud Manufacturing paradigm. Based on the definition of an appropriate web-based application, the infrastructure is able to connect the possible client requests and the relative supply chain product/process development capabilities and then attempt to find the best available solutions. In particular, the main goal of the developed system, called AMSA (Additive Manufacturing Spare parts market Application), is the definition of a common platform to supply different kinds of services that have the following common reference points in the Additive Manufacturing Technologies (DFAM, Design For Additive Manufacturing): product development, prototypes, or small series production and reverse engineering activities to obtain Computer-Aided Design (CAD) models starting from a physical object. The definition of different kinds of services allows satisfying several client needs such as innovative product definition characterized by high performance in terms of stiffness/weight ratio, the possibility of manufacturing small series, such as in the motorsport field, and the possibility of defining CAD models for the obsolete parts for which the geometrical information is missed. The AMSA platform relies on the reconfigurable supply chain that is dynamic, and it depends on the client needs. For example, when the client requires the manufacture of a small series of a component, AMSA allows the technicians to choose the best solutions in terms of delivery time, price, and logistics. Therefore, the suppliers that contribute to the definition of the dynamic supply chain have an important role. For these reasons, the AMSA platform represents an important and innovative tool that is able to link the suppliers to the customers in the best manner in order to obtain services that are characterized by a high-performance level. Therefore, a provisional model has been implemented that allows filtering the technologies according to suitable performance indexes. A specific aspect for which AMSA can be considered unique is related with the given possibility to access Design for Additive Manufacturing Services through the Web in accordance with the possible additive manufacturing technologies.

Metal additive manufacturing (AM) encapsulates the myriad of manufacturing processes available to meet industrial needs. Determining which of these AM processes is best for a specific aerospace application can be overwhelming. Based on the application, each of these AM processes has advantages and challenges. The most common metal AM methods in use include Powder Bed Fusion, Directed Energy Deposition, and various solid-state processes. Within each of these processes, there are different energy sources and feedstock requirements. Component requirements heavily affect the process determination, despite existing literature on these AM processes (often inclusive of input parameters and material properties). This article provides an overview of the considerations taken for metal AM process selection for aerospace components based on various attributes. These attributes include geometric considerations, metallurgical characteristics and properties, cost basis, post-processing, and industrialization supply chain maturity. To provide information for trade studies and selection, data on these attributes were compiled through literature reviews, internal NASA studies, as well as academic and industry partner studies and data. These studies include multiple AM components and sample build experiments to evaluate (1) material and geometric variations and constraints within the processes, (2) alloy characterization and mechanical testing, (3) pathfinder component development and hot-fire evaluations, and (4) qualification approaches. This article summarizes these results and is meant to introduce various considerations when designing a metal AM component.

Metal additive manufacturing (MAM) enables the fabrication of structures with complexity and resolution that cannot be achieved by traditional manufacturing techniques, including lattice structures. However, MAM processes inherently induce local manufacturing defects, resulting in variation between the idealised and as-manufactured geometry and potentially introducing stress concentrations that are detrimental to structural performance. Quantification of these effects on mechanical performance enables the manipulation of intended lattice geometry to enhance structural performance. However, due to the geometric complexity and small scale of geometric defects, experimental testing and numerical simulation of lattice structures are technically difficult and time-consuming. To overcome this limitation, a novel methodology for quantifying the effect of manufacturing defects on the mechanical properties of MAM lattice structural elements is proposed. This method involves the automated analysis of microscope images of as-manufactured lattice structures to generate numerical models that automate the identification of plastic hinge behaviour in node elements based on custom MAM material properties. This method is applied to Ti-6Al-4V lattice structures fabricated by selective laser melting (SLM) with a range of strut and node diameters and cell sizes. This novel method is shown to predict the effect of local manufacturing defects on bulk lattice mechanical response and provides an efficient tool for the optimisation of as-manufactured MAM lattice structures.

Additive manufacturing (AM) of metal parts combined with part redesign has a positive repercussion on cost saving. In fact, a remarkable cost reduction can be obtained if the component shape is modified to exploit AM potentialities. This paper deals with the evaluation of the production volume for which AM techniques result competitive with respect to conventional processes for the production of end-usable metal parts. For this purpose, a comparison between two different technologies for metal part fabrication, the traditional high-pressure die-casting and the direct metal laser sintering additive technique, is done with consideration of both the geometric possibilities of AM and the economic point of view. A design for additive manufacturing approach is adopted. Costs models of both processes are identified and then applied to an aeronautical component selected as case study. This research evidences that currently additive techniques can be economically convenient and competitive to traditional processes for small to medium batch production of metal parts.

Purpose The build volumes of additive manufacturing (AM) technologies are increasing in size. This improvement is associated with the growing reliability of AM processes and is driven by a rise in demand from several industries. Large-format additive manufacturing (LFAM), when referring to polymeric extrusion systems, is quite new in the field of AM. The purpose of this paper is to present a review of large-format (those with build volumes over 1 m3) fused deposition or extrusion-based AM equipment. Design/methodology/approach This paper presents an exhaustive literature review for all the publications in the field of AM in the current decade, as well as technological coverage in the news, specialized blogs and technology fairs since the year 2015. Findings This review reveals growing scientific and industrial activity, as well as in equipment, in the field of LFAM. An increase in research activity is also occurring in parallel with a growing interest, potential and adaptation of these technologies in certain industries. Originality/value This review may be the first publication to collect the majority of existing information on LFAM for polymeric extrusion systems in terms of applied extrusion technologies, commercial products, specific material research and developments, intellectual property, design and simulation solutions, as well as its practical applications.

One challenge with design automation is system transparency with adjustable granularity because of the many different forms of representation from multiple disciplines. Previous research has focused on visualization through the generation of graphs, packaging into electronic books, and model highlighting. The research presented in this paper focuses instead on a visual programming approach, commonly applied in the building industry, where design assets and external references are wrapped into visual components and managed on a canvas with information input/output relations displayed. This entails additional documentation efforts, but the visualization is arguably more useful as groups and levels of granularity are adjusted by the engineers themselves as a part of the development work. To explore visual programming and its potential benefits as a way of enabling transparency with adjustable granularity of DA systems within mechanical manufacturing industry, an existing textual design automation system was transformed into a visual one using Grasshopper® (a visual programming environment) and discussed with respect to DA system transparency, feature-based CAD, and DA system development.