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.
Also, strictly as a combo 3D-printing and engine enthusiast: Never with a GUN to my head would I install 3D printed parts in a CAR engine, let alone in an aircraft engine. This is spectacularly poor judgement on the part of the owner.
Then you are not up to speed with what the 3D printing world has to offer. You can 3D print full metal stress free parts and chances are very high that if you have flown in an airplane in the last five years that some of the parts of that plane (and I'm not talking about trim here) were made using additive processes.
Rocket engines can be 3D printed, in fact there are some engines that can only be made using that kind of technique due to internal structures.
Yes, real parts CAN be 3D printed and even used successfully.
The printing is the easy part.
The extensive testing and validation that it will actually work as intended and in your situation is the hard part.
Skip that hard part, especially for anything that flies, and you are risking lives, both those in the air and on the ground.
Seriously, just because the specs on the label say X and other docs say the running temperature is Y, does NOT mean it will work. Take the measurements in your situation, test the thing extensively on the ground.
Then, maybe, it'll be worth flying. Or, you'll be there after some hours of testing saying: "good thing I didn't try to fly with this", and still have a usable aircraft.
Depends. Some older or rare cars have no source for parts. 3D printing has been a boon to keeping them operating. However you absolutely have to use appropriate materials to avoid problems or failures, and know where it isn't feasible.
FWIW, I wouldn't hesitate to install a 3D printed air-filter housing in my car, if I had printed it myself out of e.g. PAHT or sourced it from a trusty vendor. It's not rocket science, just engineering.
Well, there are more and less important parts of the car. I wouldn't bat an eye for 3d printed dash parts or the extreme example, a cup holder, but on flip side anywhere where there is heat is potentially bad for anything 3d printed with heat that's not metal or some hard to print high temp stuff, and anywhere where mechanical robustness = safety is spot where you want something very well tested, not "I printed it and it looks light".
> Never with a GUN to my head would I install 3D printed parts in a CAR engine, let alone in an aircraft engine.
The fabrication technology doesn't matter. The qualification process, on the other hand ...
This is the primary reason why I never got a pilot's license. I suspect I would spend far too much time making sure the maintenance was up to standard and far too little actually enjoying flying.
You should be thrilled to know that any plane you will learn to fly in typically has full maintenance records for the entire life of the plane, including who did the work, their FAA certificate number, and all of the paperwork for any parts that were involved in the repair.
The shortcut is to ask the mechanic to come for a test flight after repairs. The place I learned to fly was owned by a mechanic, and the daughter ran the flight school. Given that the daughter might be test flying the mechanic's work, I trusted him to keep his planes in good shape.
> The fabrication technology doesn't matter. The qualification process, on the other hand ...
Well, yes, but... In this case the fabrication technology and the lack of qualification process likely go hand in hand. They wouldn't have a qualification process unless they were manufacturing enough of these that plastic 3d printing wouldn't be cost effective. The shortcut is the point.
Yes but are they printed with PLA or PETG, or even ABS? Or are they using material designed exactly for their use case, and tested thoroughly before being certified for flight?
Or do they get their parts from some vendor at a swap meet who spends most of his time fiddling with his Ender 3?
Neither of those is suitable for this application. Ultem or PEEK. Anything else would be a very bad idea, and even for those two you would want to do a lot of testing.
I'm sure it's fine you do it properly ([1] for example). The issue here was the utter lack of engineering, not the specific manufacturing technique (although those do seem to be highly correlated, due to low-end 3D printing having become very cheap and easy).
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/...