The advent of 3D printing, technically known as additive manufacturing (AM), has taken the hobbyist world by storm in recent years. It is a fairly simple concept where polymers, metals, concrete, paper, or ceramics are formed into complex shapes by the use of digital files. Unlike a subtractive process like CNC milling and machining, which removes material from a raw stock, additive manufacturing through printing successive layers of the aforementioned materials into the desired product. This is obviously a vast oversimplification of the process, but it does capture the basic idea around it. The aerospace industry is an excellent market to develop and manufacture parts and components which are often made from composite materials to begin with. Let’s take a look at some of the projects which have been completed, and where it is headed in the future.
Origins of 3D printing and additive manufacturing (AM)
Additive manufacturing was originated back in the 1980s, although the manufacturing processes and automation were archaic by modern standards. Still, the basic premise was the same then as now: a computer automated drawing (CAD) file provides the framework dimensions of the product which is fed into the machine.
In the early years, due to limitations in materials available which could be used in the process, the products were suitable for cosmetic applications. Methods using CAD files for automated construction were relatively commonplace but they were generally geared towards subtractive processes, i.e., removal of material via milling or lathe to get the desired shape. Additive manufacturing builds up the shape from literally nothing, virtually eliminating waste material in the process.
Where is 3D printing applied in aviation?
The great thing about 3D printing is its ability to be adapted to basically anything which the filaments available can create. It can make three dimensional shapes of any level of complexity imaginable, making it an ideal solution for rapid prototyping for a number of markets, notably aerospace, defense, and the automobile industries. It is reasonable to surmise 3D printing as a viable prototyping method for a number of components for ground support equipment prototypes. It can be used to build full-scale mockups of sun drives, gear reductions, and even circuit boards; any assembly or sub-assembly mockup can be easily built to exacting specifications.
3D printing in aviation and aerospace
So what exactly does additive manufacturing bring to the table for aerospace? There are a few areas where it can be of immediate usefulness with the use of polymers. As of 2015, aerospace and defense industries (A&D) contributed over 15% of the estimated nearly $5 billion in revenue generated by additive manufacturing. In fact, the A&D has been using 3D printing for three decades for weapon systems like missiles and rockets, and also satellites.
Rapid prototyping is an excellent application of additive manufacturing for the A&D industries. Consider the extensive process involved in creating dies for a trial modification on a given component. An exact replica can be made of non-certified polymer which offers all of the fit and finish of the final project for the sake of a non-functioning mockup at a tiny fraction the price. More importantly, it gets a scale model of the product on the showroom floor incredibly fast.
Tooling for injection molded parts does not need to be made of metal, necessarily. This is particularly important during the pre-production phase when a manufacturer only needs to make a small run of parts for the prototype aircraft or component. Once the proof of concept has been validated, they can then tweak the design if necessary and then build permanent tooling for the production line.
It is important to understand what additive manufacturing is good for, and what it is not. It is incredible at transferring a raw file into a finished model and infinite complexity. It is not particularly well suited for mass production. Each project is time consuming because it is intended to build intricate designs rather than rapid production of identical components. This is the reason why it has traditionally been used for rapid prototyping where parts are a one-off production. As the process and technology continues to improve, though, AM printers will only continue to increase in speed and efficiency.
It is not likely that AM printers will ever reach the level of productivity of tooling and die, but they will not be cast into that role, either.
What is the advantage of 3D printing?
In some applications, though, AM is a superior process than tooling. AM printing allows for a single, large component to be built from the ground up in a single unit rather than a lot of small parts being assembled for a single component. In doing so, it will allow manufacturers to reduce material waste, weight, and bulk.
There is another key advantage in AM processes which may very well trump all other applications put together. See, when legacy airframes are done being produced, particularly in defense contracts, oftentimes the manufacturer is legally obligated to destroy the dies and tooling. This is a contractual obligation which must be abided. Unfortunately, as aircraft are reaching milestones far beyond what preceding generations did or these aircraft were ever meant to do, structural components wear out.
Metal additive manufacturing offers solutions to this predicament. Exact replicas of structural components are now in reach built on an as-needed basis. Since this type of repair does not require extensive tooling and die production, the turnaround time will be absolutely unheard of. It could be measured in hours or days rather than weeks.
Also, if the weight savings associated with the Airbus A380 and the Lockheed Martin F-35 programs are any indicator, metal AM could end up cutting up to 25% in weight for replacement components. With major structural components, this could end up being in the ballpark of hundreds of pounds in weight saving, maybe even thousands depending on the size and scope of the component.
Proof of Concept
The concept checks out and has some really wonderful fanfare with it, but is it really going to work? And if so, who is doing it already and what is the scope of completed, fully functioning component repair and replacements?
The U.S. Air Force, for one, is using this method. The C-5 Super Galaxy is an unbelievable aircraft, but it has also been a chronic maintenance nightmare. It has a terrible supply chain, and has been an unreliable and troublesome platform since inception. To help ease the logistics burden of this difficult aircraft, the USAF’s Rapid Sustainment Office (RSO) have procured interior and cabin components for the C-5 fleet. As previously stated, lead times for printed components are extremely short, and interior parts can be manufactured using the exact coloration of the paintend part they are replacing, which even further reduces lead times. Think of it this way: a new interior part can be manufactured from a data file in the same evening the broken part is discovered. Even express services cannot generally deliver that quickly, and oftentimes replacement parts are not new at all but are instead stripped from an aircraft which has been decommissioned.
Boeing quite literally owns the record on the largest 3D printed item of any type. Although not technically an aircraft part, it does directly impact the production of parts. It is a gigantic jig, a wing trim and drill tool, which is to be used in the manufacture of the B777X.
The jig is about the size of a Range Rover in length and width, and about the same weight. It was produced in just about 30 hours; a comparable jig manufactured from traditional methods and products would have been somewhere around three months.
So even if this jig were manufactured in only one location, it would still be shipped easily to anywhere in the world probably within a week, certainly less than two; it would beat the expected manufacture of a traditional jig still by well over two months. This is real production value which is available right now, and it works.
Conclusion to 3D printing in aviation
While AM is not as new as it might seem, considering it’s futuristic concept and execution. The idea that lines of filament can be transformed into any shape conceivable, or metal can be formed into any sort of three dimensional object within the scope of the machine is unbelievable, yet here it is.
We are witness to a seismic shift in manufacturing process. While this is not a replacement for mass production, it will shear untold periods of time off of short notice repairs and likely add strength and save weight in the process.
It’s use in aerospace is not limited to aircraft either. GSE will surely benefit for AM technology; replacement parts can easily be printed on location by anyone with capable machinery. Manufacturers of GSE can now own and sell access rights to the construction files rather than holding onto large inventories of stock; the owner may opt to purchase the construction file and produce it on location. It is conceivable that a replacement part could be ready within the hour of purchasing plans, rather than minimums measured in days. AM stands to utterly revolutionize the MRO industry, as well as the GSE industry.