Abstract
Additive manufacturing is a strategy to produce parts with complex geometries whose process is prohibitive in cost or impossible through subtractive or formative techniques. Research groups are optimizing additive manufacturing processes to improve their performance and reduce the cost of aerospace parts. One of the emerging design techniques is self-assembly which seeks to reduce the number of parts to produce best design practices and rules. Self-assembly represents a comprehensive strategy that improves process time, product quality, cost of materials, and printability. The purpose of this chapter is to review the technological contributions that self-assembly has had in the additive manufacturing of aerospace parts. Future perspectives of the role of self-assembly in additive manufacturing are proposed. According to what was found in this research, self-assembly will facilitate the additive manufacturing of parts in various technological sectors where the manufacture of lightweight parts with high added value and restrictive regulations are required.
TopIntroduction
In the search for techniques and technologies for the low-volume production of innovative, customized, and sustainable products, the manufacturing industry has introduced additive manufacturing in the last decades (Uriondo, 2015). Additive manufacturing is the process of joining materials to produce objects from three-dimensional model data that are additively placed layer upon layer. It is regularly used to make rapid prototypes, but thanks to the optimization of processes and material properties, it is now feasible to build aerospace parts for direct assembly purposes to systems operating in the field. Until now many techniques applied in additive manufacturing have been developed, such as stereolithography (SL), inkjet printing (IJP), fused deposition modeling (FDM), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), direct metal deposition (DMD), among others, as shown in Figure 1. However, not all of them can produce metal parts. SLS, SLM, laser metal deposition (LMD), EBM, and wire and arc additive manufacturing (WAAM) processes are the most versatile processes for producing complex functional and metallic components to meet stringent requirements from the aerospace industry (Herzog, 2016; Ligon, 2017; Yusuf, 2019; Sanchez-Rexach, 2020; Alghamdi, 2021).
Figure 1. Additive manufacturing processes
The aerospace industry consists of different players including original equipment manufacturers (OEMs), maintenance, repair, and overhaul (MRO) organizations, and commercial aerospace operators (CAOs) (Singamneni, 2019). In the manufacturing process, aircraft parts manufacturers such as Boeing, Airbus, GE Aviation, Lockheed Martin, BAE Systems, and Rolls-Royce Holdings are the main interested in bringing additive manufacturing to certification standards. Aerospace components consist of many parts, but their demand is unpredictable as they replace dispersed parts required only in scheduled or unscheduled maintenance events. This brings inventory levels to the limit of 10% for spare parts, which results in unpredictable exchange times and makes them expensive. Replacement parts are of four types: rotatable, repairable, expendable, and consumable. Each type has a different replacement policy. The policy is associated with the volume of the repair and the delivery times of the supply and needs to be updated regularly to adapt to changes in the market. Traditional manufacturing mechanisms have already reached the limits of weight reduction, but the need for better and lighter designs keeps the search for manufacturing methods to tighten these limits. Until now, significant research in terms of assembly has been focused on the design of additive manufacturing principles and their integration into design generation tools such as topology optimization, while research on part consolidation has been restricted to heuristic guidelines (Crispo, 2020).
Key Terms in this Chapter
Additive Manufacturing: A 3D printing used in industrial production that allows the creation of lighter and stronger systems or parts.
Smart Memory Alloys (SMAs): Class of materials that produce a change in shape or property (rigidity, color, texture, transparency, volume) when exposed to an external stimulus.
3D Printing: A technique of manufacturing objects through the deposition of materials through a print head, nozzle, or other printing technology.
Self-Assembly: A process at which a disordered system constituted of similar or different pre-existing elements forms an organized structure or pattern through local or specific physical or chemical interactions among its elements without external stimulus.
Polyjet: 3D printing technology that produces smooth, accurate parts, prototypes, and tooling with microscopic layer resolution and accuracy down to 0.014 mm, which can produce thin walls and complex geometries using the widest range of materials available with any technology.
Binder Jetting: An additive manufacturing process where a liquid bonding agent is selectively deposited to bind powdered materials.
Powder Bed Fusion: An additive manufacturing process where heat energy selectively melts regions of a powder bed.
Material Jetting: An additive manufacturing process that uses selectively deposited droplets as building materials.
Stereolithography: A photopolymerization process that produces parts of photo-polymeric materials in a liquid state using one or more lasers to selectively cure layer upon layer of a material to a predetermined thickness, hardness, and shape.
Material Extrusion: An additive manufacturing process where a flowable material is selectively dispensed through a nozzle or orifice into a die producing a constant cross-section.