Hi all! Just wanted to share a project I have been involved with since last September. I was the TA for a class of students at Purdue University and we collaborated with students from Brigham Young University and Georgia Tech to create an almost entirely additive manufactured UAV for agricultural surveying. Boeing funded the program through their education wing and Stratasys was a huuuuuuuuuuuuuge help with printing our aircraft.
Wingspan is 89" from winglet to winglet and we are running an APM 2.6 with all the fixings as our autopilot. We are going to be flying the model in a few days but we have flown a 75% scale foam and fiberglass version and gotten all the waypoint navigation working.
Here is a top-down view of the aircraft. It is a blended wing body done almost entirely in FDM except for a small carbon spar and some hardware (hinges, nuts, bolts, etc)
Here is a cutaway schematic view of what the guts look like.
Even though we are heavier than anticipated (and what university aircraft doesn't have weight problems?), we are still around 12 lbs which is not bad for the amount of ABS we used.
We have an NDVI generating camera on board so hopefully we should be able to start spitting out some good data soon.
This project has really made us think about the value proposition that 3D printing poses. The other teams that were building aircraft at the same time went with more traditional composite layups and made gorgeous aircraft but they took forever to create all the plugs and molds and do the layup and assembly. Their airframes are much more robust than ours and can really take a beating but the amount of time sunk into fabrication is really thought provoking.
Look for a flight video in a couple weeks! I'll try to put together some more info if people are interested.
Comments
Hi Chris,
Thanks!
There were a few limitations with AM that made it a bear in some respects. The first would be that there was a sharp learning curve to efficiently make use of the process. To get the single walled structures we used, everything had to be modeled as a surface instead of a solid. That was a big change to the way that we were used to doing CAD. Those surfaces then were not supposed to connect! We needed to leave certain gaps between surfaces to let the extrusions meld together. Lots of little things like that. There is currently no software that helps you take an existing design and optimize it for AM. Well, plenty of people promise that but I haven't seen anybody really deliver, certainly not for SUAS design. So the big drawback is alllll of the experience you need to efficiently use the technology. We could have modeled the aircraft as solid extrusions but it would have doubled the skin weight (not trivial!). We had a lot of great dialogue directly with Stratasys so they deserve a big shoutout for helping us over the course of this project.
As to the internal design, all of those ribs and spars are self supporting to take advantage of the FDM process. It isn't one of the more "advanced" infills but it is very efficient. Again, it comes back to CAD work and being able to do it simply and efficiently as well as not being scared to go in and change things in the parts!
Hey Eli,
Nice work! What was the most significant limitation of using additive manufacturing to fabricate an aircraft? Is there a reason the team decided on a 'traditional' wing design (ribs and spars) over something that might exploit the benefits of additive manufacturing (I'm thinking of more organic shapes for infill)?
Thanks, Chris
Haha, Bojan, that might be slightly optimistic! It's good to dream big, though.
It would still require proper mold release just like composite molds, however it could be machined at a lower cost.... Granted, composite molds aren't exactly expensive in the first place.
I see what you're saying Eli, but you're comparing the DIY AM, no labor costs approach with paying skilled people to make a composite airframe. If you're looking at comparing apples with apples, then you have to factor in the labor (and capital!) costs of running the AM process. If you just look at material costs and not machine time, then I can probably get you a set of moulds for maybe 1000 bucks of Al, then the airframe may be USD100 or so of actual material cost each - how many did you want...?
I can see when people have this technology sitting in the lab/on the desk etc, then the incremental cost of churning out the part is attractively low (and with little mess), however the same is true of a CNC mill (except the mess...) The only difference I see is that the machining centre is a fearsome beast to tame, whereas the AM printer is a cuddly teddy bear in comparison. The capital cost of the latter is still pretty high and also probably has a short-ish useful life compared to a full blown machining centre.
I agree that the people pushing this technology are handing out favors like water to prove their point. This, in fact, proves my point, that the technology is (so far) commercially uncompetitive...
Why not just have both. I think that two axis rotary build surface is the way of the future, btw. So much less effector head movement, and no need for support material in many instances.
Andrew, I hope you didn't get the impression that I wanted to fire all machinists everywhere and replace them with AM machines :)
If you go on material costs alone, and not the cost to pay someone to do it for you, going from CAD to aircraft with AM in this particular instance would most likely have been less expensive than paying skilled workers to put it together, even if molds already existed. Then you get into the whole robustness/repairability discussion and things stop going so well for AM. It's a very, very complex issue and it's constantly changing.
I bet, at this stage, you could make a few cases for AM where it makes sense over traditional manufacturing. As our capabilities increase, however, I'm curious to see what happens. There is some great work going on at UTEP right now into integrating electronics directly into FDM parts during manufacturing and I think that opens up a whole new set of design options. Here's a link to their website: http://keck.utep.edu/advanced-additive-manufacturing-applications.html
There are a lot of people that think AM is a panacea and it can certainly be annoying when they show up on the news touting the miraculous "new" technology that's going to change everything forever, but those people also tend to be generous with funding for actual applications :)
I'm still pretty conflicted as to the merit of additive manufacturing. I see it's advantages at small scales and for complex geometry, but if this airframe would cost USD8000 in the real world, I could machine a set of Al moulds for a (lighter!) composite airframe for that kind of money!
I think the people who reckon additive manufacturing is going to revolutionize things are slightly delusional. It will make some changes, but "old-school" technologies still have many advantages!
Don't forget, the advantage of throwing it into beta and coming to a quick stop. You can make a nice belly flop from half a meter up.
I've always been curious about designing a wireless remote system at this scale. A small actuator built into the hub, controlled via bluetooth(or?), powered via ?. No slip rings or mechanical linkages.
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