Metal Additive Manufacturing. Ehsan Toyserkani

components are widely used in the aerospace industry. Any weight reduction is translated into a considerable amount of money saved in terms of the part price itself as well as fuel consumption (Figure 1.4).

Figure 1.3 Complex parts made by AM. The spherical nest has three spheres inside.

Figure 1.4 Lightweight structure made by AM. In this typical bracket, the weight has been reduced by 60% when the mechanical strength and stiffness remain the same.

       Parts consolidation: Mechanical assemblies are common in industrial products. In complex mechanical machines, there are more than tens, hundreds, or even thousands of components that are either welded, or bolted, or press‐fit to each other. Parts consolidation offers many advantages due to the reduction of the number of individual parts needed to be designed, manufactured, and assembled to form the final system. Part consolidations offer multiple benefits: (i) design simplification; (ii) reduction of overall project costs; (iii) reduction of material loss; (iv) reduction of weight; (v) reduction of overall risk where the number of risks associated with too many suppliers of individual parts drops; (vi) better overall performance, as it enables geometries that are desirable but cannot be made with conventional manufacturing.

AM allows for parts consolidation, even removing the need for assembly in some cases. Several applications of AM have obvious benefits for fostering product performance through lightweighting/consolidation without compromising high strength are: optimizing heat sinks to dissipate heat flux better, optimizing fluid flow to minimize drag forces, and optimizing energy absorption to minimize energy consumption. Figure 1.5 shows an example conducted by GE Additive. Almost 300 parts were consolidated in one part for the A‐CT7 engine frame. This consolidation also reduced the seven assemblies to one where more than 10‐pound weight was chopped off.

Figure 1.5 Consolidation of around 300 parts to one part printed by AM.

      Source: Courtesy of GE Additive, open access [7], reproduced under the Creative Commons License.

       Functionally graded materials (FGMs) and structures (FGSs): The integration of multiple advanced materials into one component is one of the most rapidly developing areas of AM technology. The capability to create multiphase materials with gradual variations in compositions is one of the important features of AM. During the layer‐by‐layer step of AM processes, the material composition can gradually be altered to obtain the desired functionality. AM also enables the development of FGSs with a single‐phase material, where the density is gradually changed through the addition of cellular/lattice structures; and embedding objects (e.g. sensors) within structures. Among AM processes, DED is the most promising technology to develop such structures, where different powders can be switched insitu to develop desired composition and alloys. Figure 1.6 shows different FGMs that can effectively be developed by DED. Figure 1.7 shows a cutting tool with an embedded fiber optic, as an FGS, developed by an AM‐based process.

       Parts with conformal cooling channels for increased productivity: Cooling systems play a vital role in the productivity and performance of many parts. For example, in an injection molding process, the cooling period of a production cycle counts for more than 40% of cycle time. If this period drops by means of taking the heat out of the mold, the productivity increases dramatically. In an active antenna, developing conformal channels will be very important as the generated heat can be dissipated from the zone much effectively, not to affect the antenna performance. With AM, designers can have much more freedom to incorporate conformal cooling channels into their designs that facilitates uniform cooling over the entire surface. Sub‐conformal channels can be included in the optimization process. Figure 1.8 shows a design of an insert used in molds. The design includes a conformal cooling channel wherein the support cells are used to enhance the heat transfer.

       Parts repair and refurbishment: Machining errors or last‐minute engineering changes can affect on‐time delivery of tooling and potentially impact the introduction date of a new product. AM, especially DED processes, can be applied as a safe technology to repair tooling, especially on critical contacting surfaces. AM increases tool life and, in many cases, can save a high‐value tool that would otherwise need to be replaced. Figure 1.9 shows an LDED process used in the in‐situ repair of turbine blades.

Figure 1.6 Functionally graded materials (FGMs); (a) Laser DED with multiple powder feeders is widely used for FGMs; (b) FGM with two alloys with gradual interface (c) FGM with two alloys with one sharp interface, (d) FGM with multiple interfaces, (e) FGM with three alloys, (f) FGM with selective deposition of secondary alloy.

      Source: Redrawn and adapted from [8].

Figure 1.7 A fiber optic embedded in a metallic cutting part using a combined AM‐based process.

      Source: Republished with permission from Elsevier [9].

Figure 1.8 A mold insert with (a) conformal cooling channels, (b) conformal and lattice structures to improve heat dissipation.

      Source: Republished with permission from Elsevier [10].

Figure 1.9 LDED used to rebuild turbine blades.

      Source: Courtesy of Rolls Royce [11].

       A solution to supply shortages in critical crises: Interruption to the global supply chain during crises can be catastrophic to