## 3 Industrial Applications
### Aerospace  
One of the earliest adopters of AM technologies is the aerospace industry. All sectors of this industry such as commercial aircraft, military applications, and missile systems are applying AM technologies [10]. The capability of metal AM to perform rapid tooling and repairing, fabricate freeform and complex geometries, and consolidate parts, makes it ideal for the aerospace applications [76]. Moreover, the aerospace components are commonly made of difficult to machine materials such as high resistant super-alloys [77].  
General Electric (GE) Aviation uses Concept Laser and Arcam metal printers to manufacture fuel nozzles for its new LEAP engine [10,78]. Figure 5a shows the LEAP fuel nozzle, which is 25% lighter and stronger than the original nozzle. More importantly, this component boosts the fuel efficiency of the engine up to 15% higher than the previous best CFM56 engines [77]. Figure 5b shows another additive manufactured product, the GE Turboprop engine, which features subassemblies with just 12 parts, in stark comparison to the original engine that had 855 parts. [PERSON] reported that the novel AM Turboprop also boosts the fuel burn efficiency by up to 20%.  
Figure 4: Automotive additive manufactured components: (**a**) Steering knuckle [68], (**b**) Bugatti brake caliper [72], (**c**) Bugatti topology optimised bracket [72], and (**d**) Lightweight structure made in Scalmalloy aluminum [74].  
Figure 5: Aerospace additive manufactured components [77]: (**a**) GE Leap Nozzle, (**b**) GE Turboprop Engine, (**c**) Airbus A350 XWB jet wing bracket, and (**d**) Titanium door hinge.  
Furthermore, Airbus is using EOS and Concept Laser machines to manufacture metal brackets and bleed pipes for its aircrafts. Moreover, this company is producing large-scale AM airframe components in collaboration with Aronic [10]. Figure 5c shows an AM wing bracket that is printed with a Concept Laser machine, for the next generation Airbus A350 XWB jets [77]. Figure 5d shows an AM lightweight Titanium Ti64 turbine cover door hinge, used on an Airbus A380, printed with an EOS laser sintering machine. Another step of this company toward use of metal AM is the development of optimised A320 components and redesigning Titanium parts of the A350 [5].  
In addition to the above, DED technologies have received considerable attention from the aerospace industry in recent years. For instance, LMD technology was used for fabricating the impeller blades of turbomachinery as well as repairing damaged areas [79]. This metal AM process provides 'Near-Net-Shape' geometry [80]. DED technologies are also used for the repair of turbine airfoils, engine combustion chambers, and blisks [10]. In another research study, [PERSON] et al. [81] applied LENS technology to repair defective voids in turbine airfoils. The results showed that the repaired airfoil matched the geometry of the original geometry with the 0.03 mm mean accuracy, improved the carbon footprint by 45% and increased the total energy saving by up to 36%.  
From the above, it can be seen that the aerospace industry has already started to receive benefits from adoption of AM technologies. According to a report published by [PERSON] et al. [82], the aerospace industry benefits from AM technologies in different ways as follow: Lead time is shortened by up to 70%; Non-recurring costs is reduced by up to 45%; and mass is decreased by 35% or more.