[averynicepen]

3D printing is to mechanical engineering what vibe coding is to computer science.

With the rise of accessible 3D printers that can print engineering materials, there are a lot of people who try to create functional parts without any engineering background. Loading conditions, material properties, failure modes, and fatigue cycling are all important but invisible engineering steps that must be taken for a part to function safely.

As a consumer with a 3D printer, none of this is apparent when you look at a static, non-moving part. Even when you do start to learn more technical details like glass transition temperature, non-isotropic strength, and material creep, it's still not enough to cover everything you need to consider.

Much of this is also taught experimentally, not analytically - everyone will tell you "increasing walls increases strength more than increasing infill", but very few can actually point to the area moment of inertia equation that explains why.

3D printing has been an incredible boon for increasing accessibility for making parts in small businesses, but it has also allowed for big mistakes to be made by small players. My interpretation is the airshow vendor is probably one of these "small businesses".

[potato3732842]

You don't need to be able to mathematically jerk the equation off to understand why increasing material at the perimeter adds more strength than the center (within reason and in typical cases) or why you probably shouldn't use something that melts around 200deg in an engine bay.

[Doxin]

Note that the actual material used has a glass transition temperature around 50 degrees, not 200. If the part was actually made from ABS-CF (as the pilot thought it was) it'd stand a decent chance of surviving for a long time given that it gets a lot of air cooling.

[jibe]

Hmm, apparently it would have been useful..

[cedilla]

Ehh.

Everything you need to consider is really not that much when it comes to most typical consumer 3d printing projects. Mostly because they are usually about stuff like "fixing a broken tashcan". The engineers who made that bullshit plastic part that broke after a year probably knew all about area moment of inertia, but that doesn't mean I need to to print a replacement part that lasts longer - or not, in which case I'll just iterate on my process.

I really don't get the dismissiveness, and frankly, I've never experienced that from engineers in my life. They just seem delighted when someone, kid or adult, tinkes with additive manufacturing.

[averynicepen]

Hmm, I suppose the analogy could be interpreted as dismissive, which is not my intent.

I think both vibe coding and 3D printing are wonderful things. Lowering the barrier to entry and increasing technology accessibility allows those without formal training to create incredibly capable things that were previously difficult or not possible to do.

What I meant to specifically highlight is the 3D printing of functional parts that have some level of impact on safety, things that can lead to significant property damage, harm, or loss of life. Common examples include 3D printed car parts (so many) and load bearing components in all sorts of applications (bike mounts, TV mounts, brackets, I even saw a ceiling mounted pull-up bar once).

This isn't to say it can't or shouldn't be done. What I'm saying is that both on the digital side (files for personal use) and the production/sale side (selling finished parts), there is no guarantee of engineering due diligence. 3D printers enable low volume small businesses to exist, but it also means that, purposefully or not, their size means they can go quite a while without running into safety regulations and standards meant to keep people safe.

[phoronixrly]

I call bullshit. 3d-printing is just a manufacturing method. Basic woodworking is much cheaper and more accessible than 3d-printing, do you call it vibe-coding?

[defrost]

If you carve a wooden part with "the right shape" for an engineering application that the part lacks the physical properties that allow it to perform under load stress ... then yes, that's vibe carving.

Looks good - falls apart in practice, and a junior can't tell the difference as they "look the same" to the inexperienced eye.

From practical experience, you cannot just replace a tyre on a car with any old bit of wood - you really need to use hard wearing mulga (or equivilant) as an emergency skid. (And replace that as soon as possible)