How is AM being implemented in the aerospace industry?
According to the report from the Royal Academy of Engineering in 2013, “the largest adopter has been the aerospace industry with the entrance of metals-fed AM machines into the industry in 2011, resulting in good take-up of the technology owing to advantages of speed, cost and materials rationalization.”
In 2015, there are certain companies that have already implemented AM technology. For example, according to the McKinsey report, Boeing has employed 3D printers to produce 200 part numbers for ten different types of aircraft (http://www.mckinsey.com/insights/manufacturing/3-d_printing_takes_shape). The Advanced Manufacturing Research Centre (AMRC) at the University of Sheffield has already produced and successfully tested a 3D printed drone. FILTON, GE, and BAE Systems are some other examples of AM used in aerospace industry.
AM enables remarkable weight reduction by optimizing design characteristics and outcomes. One of the examples of this is the seat buckle used in aircraft. In terms of the savings from AM technology in aerospace industry, lightness is one of the most critical quality characteristics. A seat buckle produced with traditional manufacturing methods weighs 155 grams while a seat buckle produced with AM is about 70 grams. In conclusion, considering that the Airbus 380 contains 853 economy class seats, a 72.5 kg reduction is possible thanks to AM. One kilogram saved in an aircraft results in approximately USD3,000 of savings of fuel per year. According to Boeing research, a one pound weight reduction from each aircraft of a 600+ fleet of commercial aircraft could save about 11,000 gallons of fuel annually. Considering that fuel absorbs 35% of an airline’s annual revenues, AM has a huge potential to reduce costs in airline services. As a summary, AM is seen as one of the most effective ways to produce lighter components and parts in the aerospace industry.
According to Brimley et al.’s  report, the US Army’s Rapid Equipping Force utilizes mobile AM labs in Afghanistan to manufacture quick replacements for products.
Made In Space, the producer of Portal, the first 3D Printer to go to space on board of the International Space Station (ISS, accumulate over 30,000 hours of 3D printing technology testing and 400+ parabolas of airborne microgravity test flights. Now the Additive Manufacturing Facility on board of the ISS is successfully producing simple tools and test parts opening a new research gate to produce in space, namely in-space manufacturing.
Furthermore, Crandall  reports that NASA also used 70 additively manufactured parts (such as flame-retardant vents, camera mounts, and housings) with Fused Deposition Modeling technology for the Mars Rover test vehicles.
As another example, in 1990s, Boeing's Rocketdyne propulsion and power section utilized selective laser sintering (SLS) to manufacture low volumes of parts such as for the space lab and space shuttles (Rapid Prototyping Report, 1999). NASA's Jet Propulsion lab has also used SLS for producing parts launched into the upper atmosphere .
AM has been accepted as an effective manufacturing method for several reasons in the aerospace industry. First, using AM techniques, it is possible to decrease the “buy to fly ratio”, which is a ratio of the sum of material consumed to produce one unit of the final part. Within traditional methods, this ratio is around 20:1 while AM results in approximately 1:1 . Second, the utilization of material consumption is maximized through AM. As stated by Horn & Henrrysson , the raw material (powder metal in most cases) may be recycled several times when AM is implemented as the main manufacturing approach. In addition to this advantage, especially, direct metal additive manufacturing results in a better cost-effective route for manufacturing complex parts made of gamma phase titanium aluminide in the aerospace industry. It is also stated that it is possible via AM to manufacture some products that were impossible in the past .
Lyons  from Boeing Research and Technology reports that SLS is implemented in producing lightweight, highly integrated systems and payload components at Boeing, considering the light weight as one of the most critical quality characteristics in the aerospace industry. Lyons also asserts that before applying AM in aerospace industry, the material and process should be analyzed in-depth. Lyons  underlines that “Typical SLS machines use 75-Watt carbon dioxide (CO2) lasers that have a 500-μm spot size. The laser spot moves at speeds of up to 10 meters per second over layers of nylon powder only 100 μm thick; each layer is completed in approximately 60 seconds”.
Lyons  reports that Boeing and its partners developed a method using SLS for controlling the temperature in part-building platforms. Similarly, Lyons  indicates that AM is used in flame-retardant polyamides, as another research area for the aerospace industry. Boeing implemented SLS in order to optimize temperature related quality characteristics and to pass flammability tests.
The aerospace industry is required to meet very strict and complex requirements and regulations for all materials, components, and parts used in the final products. Lyons  expresses that complicated manufacturing processes motivated Boeing to implement AM. Considering the complexity in the production processes, Lyons  gives some of the quality characteristics employed in the aerospace industry even for the simplest components as specific strengths, fatigue resistance, creep resistance, use temperature, survival temperature, several tests of flammability, smoke release and toxicity, electric conductivity, multiple chemical sensitivities, radiation sensitivity, appearance, processing sustainability, and cost. Lyons  and Shinbara  state that three new performance characteristics were developed for SLS polymer materials in the aerospace industry. They are 1) operating at higher temperatures, 2) better flame resistance, and 3) adjustable electrical conductivity. In addition to those characteristics, Lyons  also adds other physical performance characteristics such as mechanical toughness, resistance to chemical attack, resistance to ultraviolet radiation, dimensional fidelity, and viable economics.
In a different application, as reported by NASA on its web site, NASA's Advanced Food Technology program, with its partners, investigates the opportunities of using 3D printers for making food in space especially for long-term missions, considering that refrigeration and freezing consumes significant spacecraft resources. NASA has funded USD25,000 on the first phase of this program so far.
In July 2016, NASA’s Juno spacecraft entered Jupiter’s orbit during a very difficult 25 minute Jupiter Orbital Insertion (JOI), later NASA received several radio tones throughout the night that indicated successes, and eventually Juno signaled that it had entered orbit – one second off from predictions. But it was also a huge event for the 3D printing world, as Juno is the first ever spacecraft to fly 3D printed parts – a dozen or so titanium waveguide brackets made by Lockheed Martin.