The past few decades have seen substantial growth in Additive Manufacturing (AM) technologies. However, this growth has mainly been process-driven. The evolution of engineering design to take advantage of the possibilities afforded by AM and to manage the constraints associated with the technology has lagged behind. This paper presents the major opportunities, constraints, and economic considerations for Design for Additive Manufacturing. It explores issues related to design and redesign for direct and indirect AM production. It also highlights key industrial applications, outlines future challenges, and identifies promising directions for research and the exploitation of AM's full potential in industry.Design, Manufacturing, Additive Manufacturing

Depositing large components (.10 kg) in titanium, aluminium, steel and other metals is possible using Wire þ Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire þ Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti-6Al-4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed.

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With increasing emphasis on sustainability, Additive Layer Manufacturing (ALM) offers significant advantages in terms of reduced buy-to-fly ratios and improved design flexibility. Plasma Wire Deposition is a novel ALM technique in which plasma welding and wire feeding are combined. In the present work, a working envelope for the process using Ti-6Al-4V was developed, and regression models were calculated for Total Wall Width, Effective Wall Width and Layer Height. The Plasma Wire Deposition process is able to produce straight walls of widths up to 17.4 mm giving a maximum effective wall width after machining of 15.9 mm, which is considerably wider than competing processes. In addition, for Ti-6Al-4V the deposition efficiency averages 93% and the maximum deposition rate is 1.8 kg/h. Coarse columnar grains of β phase grew from the base during deposition, which transformed into a Widmanstätten structure of α

Mechanical property anisotropy is one of the issues that are limiting the industrial adoption of additive manufacturing (AM) Ti-6Al-4V components. To improve the deposits' microstructure, the effect of high-pressure interpass rolling was evaluated, and a flat and a profiled roller were compared. The microstructure was changed from large columnar prior b grains that traversed the component to equiaxed grains that were between 56 and 139 lm in size. The repetitive variation in Widmansta¨tten a lamellae size was retained; however, with rolling, the overall size was reduced. A ''fundamental study'' was used to gain insight into the microstructural changes that occurred due to the combination of deformation and deposition. High-pressure interpass rolling can overcome many of the shortcomings of AM, potentially aiding industrial implementation of the process.

Nowadays, there is a great manufacturing trend in producing higher quality net-shape components of challenging geometries. One of the major challenges faced by additive manufacturing (AM) is the residual stresses generated during AM part fabrication often leading to unacceptable distortions and degradation of mechanical properties. Therefore, gaining insight into residual strain/stress distribution is essential for ensuring acceptable quality and performance of high-tech AM parts. This research is aimed at comparing microstructure and residual stress built-up in Ti-6Al-4V AM components produced by Wire + Arc Additive Manufacturing (WAAM) and by laser cladding process (CLAD). 2 Introduction Additive manufacturing, often called 3D printing is nowadays among the most studied processes. AM is a key technique of a great potential in reducing high cost of producing conventional components made from relatively expensive materials such as titanium alloys. The worldwide Ti component production is constrained due to the high cost of Ti in comparison to other materials. Therefore, AM techniques aiming towards zero waste manufacturing are identified as potential prosperous routes in broadening Ti parts fabrication that are usually affected by often difficult and extensive machining. Ti is very broadly used in space, aerospace, nuclear, marine and chemical industries by virtue of its desirable properties such as high specific strength combined with excellent corrosion and oxidation resistance [1]. Although Ti is a very cherished material, its use in AM processes is also relatively challenging because of its low thermal conductivity which results in drawbacks such as uneven temperature field and poor interlamination integration [2]. Avoiding extensive machining by a near netshape successive layers fabrication can reduce the Ti parts production cost significantly. The buy-tofly ratio for a part machined from forged billet is typically 10-20 [3] and can potentially drop to nearly 1 when produced by AM techniques. There are numerous AM techniques that are capable of producing complex geometries close to their net-shape. Simply, AM techniques can be classified according to feeding technique, heat source or feedstock material. Powder bed, blown power and wire feed are the main AM techniques using heat sources such as electron beam, laser or electric arc, while the most common feedstock materials are powder or wire. Despite the similarity of AM

The applications of Additive Manufacturing (AM) have been grown up rapidly in various industries in the past few decades. Among them, aerospace has been attracted more attention due to heavy investment of the principal aviation companies for developing the AM industrial applications. However, many studies have been going on to make it more versatile and safer technology and require making development in novel materials, technologies, process design, and cost efficiency. As a matter of fact, AM has a great potential to make a revolution in the global parts manufacturing and distribution while offering less complexity, lower cost, and energy consumption, and very highly customization. The current paper aims to review the last updates on AM technologies, material issues, postprocesses, and design aspects, particularly in the aviation industry. Moreover, the AM process is investigated economically including various cost models, spare part digitalization and environmental consequences. This review would be helpfully applied in both academia and industry as well.

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