At a glance, that looks like worse than merely the negligence of using a new technology.
The whole point of 3D printing is that the material is moldable when hot but rigid when it cools. And people really should be aware that engines get hot.
Also it's insane that they used a bolted joint with plastics on a critical place, the plastic will creep under the clamp load and will lose clamp force.
This is the mechanical equivalent of vibe coding. 3D printing itself isn't exactly to blame but the negligence of the company that created and sold this part and omitted it's use from an inspection.
Just because a part has the shape of an engineered part does not make it compatible, strong, safe, and fit for purpose. This part could have likely been fine if it used a different material such as Ultem.
The part was claimed to be ABS-CF. UK AAIB tested the part and found it to have a Tg of approximately 53C. The Tg of ABS is far higher, around 100C. I suspect that the part may have been accidentally printed with PLA-CF (which has a Tg of approximately 55C.)
The original part was fiberglass/epoxy with the epoxy having a Tg of 84C.
The person that installed should have thought more carefully about it. But the person that printed it and sold it should face some legal repercussions. Totally irresponsible what they did.
so, if you were thinking "who would use a 3D-printed part", remember that it may otherwise also have been made with some liquid material, but using a mold, and perhaps two parts using a mold that are joined with re-heating etc. - and now it no longer sounds so outlandish.
Taken at face value, this is engineering negligence. I've done industrial design with plastics and 3D printed parts. Regardless of the forming techniques, with plastics you still need to consider properties like minimum melting temperatures, tensile stress, and so forth. Then you must test that rigorously. This is all standard procedure. That information is in the data sheet for the material.
I did a quick search and found that many plastics are governed by ISO 11357 test standard [1]. Some of the plastics I have worked with used this standard.
And this is why (at least for the US) aviation parts have such an onerous paperwork overhead, why a seemingly cheap part like a $.50 bolt balloons to much greater. Granted this aircraft was a UK-equivalent to "experimental" in the US, where you can pretty much do anything to it, I'm of the opinion that doesn't excuse maintenance and adding fly-by-night parts that borders on negligence. Stick to a minimum standard, if not just out of shame of something that could happen.
I wonder if just including the aluminum tube that was effectively acting as a heat break would have been enough...
Really it seems like a problem of not understanding the environment, and testing (with margins) your replacement in it... 3D printing seems nearly entirely unrelated apart from enabling people to make parts.
An injection molded part, for a close more traditional analogue, would presumably have failed the same way here.
Also the glass transition temperature reported in the report is suspiciously low for ABS and the only source on the material is the owner saying the person they bought it from said... I wonder if it was just outright made out of the wrong material by accident.
I showed this to a pilot friend of mine out of curiosity, he noted that this type of aircraft is usually kit built / home built. So the fact a part of it was 3D printed was not a total shock.
Hah! I've actually 3D printed a part of an intake before. Just as a prototype, to allow me to get a Keihin carb on a motorcycle that had a CV carb.
Printed it on an SLA machine though! I was concerned enough about chemical attack even then, even though it was a temporary part. Never really thought about doing it in filament.
Hardware engineering is hard. Especially for any safety critical component.
In this case engineering was done by someone, who either did not understand the material he was working with, or the operating conditions in which that part was deployed.
Obviously no testing or any kind of proper engineering was done to create requirements validate them and verify them.
Being able to design a 3D model and print it does not mean you are done with engineering. It is just one step in a very long chain, which is needed to produce devices which stand up to their use.
correction to the title: the plane crashed because the owner is a moron, not because he bought a 3d printed part but because he failed to ensure his provider is trustworthy and instead used a fly-by-night nobody to fit a machine that can kill him at any moment.
I hope 3-D printing becomes obsolete when robots can achieve the same efficiency with using the standard construction materials. That should take away all benefits of 3-D printing over regular builds.
I'm massively paranoid that some cable clips I printed that will sit on a circuit board will perish in the heat. Meanwhile, some idiot couldn't care less about thermal stability for flight hardware!
Aside from the failure it looks like it wasn't the best print to start with. Lots of rashing from support and curling at the edges. You can see on the flats where the support was and the outer curve of the elbow looks like it likely wasn't airtight.
Appears to me to be printed with the inlet facing upwards.
Better support planning, settings and possibly orientation may have helped.
Other commenters are saying it was likely PLA-CF, which I totally agree with based on the testing, but I can't help but think there is no possible way the person printing this item did not know that.
I doubt the print would have come off as good as it did when using ABS-CF settings on PLA-CF.
35 comments
[ 0.27 ms ] story [ 50.7 ms ] threadedit: It was ABS-CF, which shouldn't be used under stress long-term in higher temperatures than maybe 65-70°C, or lower depending on the blend.
CF-ABS (or so claimed)
[1] https://www.gov.uk/aaib-reports/aaib-investigation-to-cozy-m...
Material was CF-ABS
The whole point of 3D printing is that the material is moldable when hot but rigid when it cools. And people really should be aware that engines get hot.
Also it's insane that they used a bolted joint with plastics on a critical place, the plastic will creep under the clamp load and will lose clamp force.
Just because a part has the shape of an engineered part does not make it compatible, strong, safe, and fit for purpose. This part could have likely been fine if it used a different material such as Ultem.
The original part was fiberglass/epoxy with the epoxy having a Tg of 84C.
https://duckduckgo.com/?q=plastic+air+induction+elbow&ia=ima...
so, if you were thinking "who would use a 3D-printed part", remember that it may otherwise also have been made with some liquid material, but using a mold, and perhaps two parts using a mold that are joined with re-heating etc. - and now it no longer sounds so outlandish.
I did a quick search and found that many plastics are governed by ISO 11357 test standard [1]. Some of the plastics I have worked with used this standard.
A spec sheet for that material is here [2].
[1]: https://www.iso.org/standard/83904.html
[2]: https://um-support-files.ultimaker.com/materials/1.75mm/tds/...
Really it seems like a problem of not understanding the environment, and testing (with margins) your replacement in it... 3D printing seems nearly entirely unrelated apart from enabling people to make parts.
An injection molded part, for a close more traditional analogue, would presumably have failed the same way here.
Also the glass transition temperature reported in the report is suspiciously low for ABS and the only source on the material is the owner saying the person they bought it from said... I wonder if it was just outright made out of the wrong material by accident.
Edit:
https://en.wikipedia.org/wiki/Rutan_VariEze
https://en.wikipedia.org/wiki/Burt_Rutan
edit: nvm, i found my answer in the actual report.
Printed it on an SLA machine though! I was concerned enough about chemical attack even then, even though it was a temporary part. Never really thought about doing it in filament.
In this case engineering was done by someone, who either did not understand the material he was working with, or the operating conditions in which that part was deployed.
Obviously no testing or any kind of proper engineering was done to create requirements validate them and verify them.
Being able to design a 3D model and print it does not mean you are done with engineering. It is just one step in a very long chain, which is needed to produce devices which stand up to their use.
Absurd what people will do to save a buck.
Aside from the failure it looks like it wasn't the best print to start with. Lots of rashing from support and curling at the edges. You can see on the flats where the support was and the outer curve of the elbow looks like it likely wasn't airtight. Appears to me to be printed with the inlet facing upwards.
Better support planning, settings and possibly orientation may have helped.
Other commenters are saying it was likely PLA-CF, which I totally agree with based on the testing, but I can't help but think there is no possible way the person printing this item did not know that. I doubt the print would have come off as good as it did when using ABS-CF settings on PLA-CF.
Big chain of poor choices.