# Would it be possible to use 3D printed node based structures to make cheaper GA planes?

A car boasting 700HP and under the U.S LSA weight limit was just announced by Divergent Technologies. I was curious on peoples thoughts on using this technique in planes. Obviously there are some issues with the surface of the structure bearing load, but I imagine these could be overcome.

3D printing is unlikely to make anything cheaper in the near future. With current printing technologies it's an order or magnitude or two more expensive per unit than volume manufacturing techniques such as extrusion or injection moulding.

It's notable that the company you link to chose to make a supercar rather than a low-cost small car. There's little price competition in that market, as brand loyalty dominates. Most supercars are bought as status symbols or for fun rather than for their actual road performance. Most of the incumbents manufacture very small runs with a lot of hand assembly: exactly the kind of manufacturing that 3D printing is competitive for. On top of that, because of the status symbol marketing, there's huge room for new players to differentiate based on a green image. Tesla has done this in the last few years, which is why some of DMF's marketing material focuses on dissing electric cars.

Runs are small in GA too, so there's potentially a wider niche for these techniques to fit into. The market that would most closely fit IMO is kit aircraft. A kit that's primarily 3D printed parts joined by standard spars, with a flexible outer shell, could have shorter lead times and less tooling cost.

After discussing this with some mechanical engineer colleagues today, they pointed out how 3D printing of metals is now being used as a complement to CNC machining in the rocket industry. For a part that has to be machined from a single piece of metal, they 3D print a shell that's slightly larger than the required shape, and then machine it to the correct shape. It allows you to achieve the tolerances you get from machining (which 3D printing can't yet deliver), but without the waste you get from cutting down a solid block.

It's an aside to the main question, but it's a way that 3D printing could be used to reduce the cost of some components and allow designs that would have been economically infeasible.

• If I read your first paragraph it seems like your answer is "no". But GA aircraft are, as you mention further down, produced in small numbers. It seems that 3D printing as a competitive production technology when the production volume is low. The lower tooling costs offset the higher unit costs. In the end your answer tends to be a "yes", but I am not sure. – DeltaLima Jun 26 '15 at 21:14
• @DeltaLima There's small numbers and small numbers. Even a run as small as a few hundred units can be a lot more expensive with 3D printing. While some 3D printing techniques could make even smaller runs feasible from a manufacturing point of view, it wouldn't reduce the one-off cost of designing and certifying a new type. That's why I say it could find a niche in kit aircraft, which mostly fly on a Permit to Fly rather than a type certificate. – Dan Hulme Jun 27 '15 at 7:00

3D printing is still an emerging technology. It's far from practical as a primary manufacturing method, but it is certainly possible as parts production - it is vastly cheaper to maintain a database of instructions than a warehouse of parts. Printers capable of making 1000cm$^3$ parts out of structural plastics like ABS are readily available on Amazon for \$600. If you need bigger, the price goes up. A lot.

Airbus at one point was experimenting with 3D printing of sintered metals. If that ever works out it will revolutionise the spare parts industry, probably not in a good way.

As Dan said, kit and model aircraft will be early adopters.

Obligatory xkcd

I work at a company that routinely uses 3D printers for design of new components - although not for the aviation industry. As the other posters have said, these parts are not cheaper than parts produced using other technologies. However, our 3D printers have vastly increased the efficiency (and decreased cost) at which we can design new products. Although 3D modeling of new parts in software goes a long way, being able to actually use the part in a prototype is a complete game changer. And by printing out modified designs we can dramatically shorten the feedback loop to arrive at the "right" design.

I would suspect that use of this technology by aircraft manufactuers could therefore decrease the cost of design which might result in decreased costs overall.

The comments here are on point however I would like to mention that its very actively being looked into. GE successfully 3D printed a full working mini jet engine. That in and of its self is a pretty cool accomplishment. However it should be noted that the cost may not have been fully considered for that particular project.

GE also has at least one FAA cleared part that is 3D printed. It is a part for the GE90-94B jet engine.

The only kind of 3D printing process which produces structures fit for the load/weight ratios usual in aviation is electron beam printing. It uses titanium, stainless steel or aluminium grains (feels and looks much like sand) and heats that up locally to the melting point in an inert atmosphere, layer by layer. The advantages are:

• Very fine structure, better than what is achievable by casting.
• No molds.
• Geometries which would be impossible to mold by casting or milling.

• Rough surface; minimum roughness is given by grain size.
• The surface imperfections translate into a notching effect, so the actually usable cross section is smaller than what is produced, which reduces material efficiency.
• Manufacturing cost hardly goes down with the number of parts.

The only areas where this has been used gainfully so far are special cases:

• Titanium implants, where replacements for bone structures can be custom-made within less than 24 hours. The rough surface is an advantage here, because it allows better integration into the body.
• Replacement parts in case a JIT assembly line is compromised by one part missing.
• Impossible geometries like hollow core pins for injection molding. The channels for the cooling water inside can have a corkscrew shape, one for the inflow, and one interleaved for the outflow. The gains in process efficiency can be immense.

In general, a 3D printed airplane is possible. Cost savings can be realized for a few special parts, but the general structure would certainly be more expensive. Consider that the surface roughness means that at least aerodynamic surfaces and contact areas with other parts need to be planed (e.g. by milling) after 3D printing.

While a single-issue sports car might be cheaper to produce this way, I very much doubt that GA manufacturing will benefit from 3D printing soon, even with the reduced production volume of today, except for some special parts.