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Comment by random3 | Hacker News Reader

Yet this is part correct, part wrong. Indeed every industry has some unique challenges that are not directly solvable. However, while a cast is absurdly expensive, the problem is being solved in large part by software in the FDM (3D printing) space and it's changing how things are built.

edit: this doesn't invalidate the OP thesis, which I strongly agree with. Except that it's not just engineers, this is a more general thing across many fields.

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Do you work in this field or are you just reading that? I’ve been out of the game for over five years now, but as far as I can tell from people I know still in that world, if you’re going to make more than like … 3 of a part, casting is going to be much cheaper. And while you can do some prototyping on 3d prints, the nature of the material winds up different from a cast part.

I'm not building molds, but I'm actively researching the field in conjunction with my work. Based on what I'm seeing and reading things have changed in the last few years dramatically. Concretely in the selective laser sintering (SLS) Formlabs is redefining small-scale manufacturing. But don't get distracted by the "small-scale". It's a bit like how small servers replaced mainframes. Production lines are getting replaced by much more versatile alternatives.

Formlabs recently launched a $80K industrial-grade machine that works better than it's $500K alternatives.

https://formlabs.com/blog/announcing-fuse-x1-industrial-sls/ https://formlabs.com/blog/diy-injection-molding/ https://www.youtube.com/watch?v=0TvjUVdn3YQ&t=2586s

Formlabs is used by Tesla to print car parts to Ukraine to print drones.

The thing about SLS is that it works with metal too. So you have startups like Divergent (recently raised $290M) in LA printing car engines https://www.latimes.com/b2b/space-tech/story/2026-06-23/dive...

Note that rocket engines are 3d printed too from SpaceX to India's Sky Roots https://www.selfcad.com/blog/how-spacex-uses-additive-manufa... https://3dprintingindustry.com/news/skyroots-vikram-1-reache...

So is injection molding more effective than additive manufacturing? This question is a bit like "no more interesting than the question of whether a submarine can swim".

But while you have metal at industrial scale you have "desktop" metal printers for ~$10K https://all3dp.com/4/first-look-at-the-scrap-1-desktop-metal...

You'd need hundreds, if not thousands, of parts to justify a mold for casting. And even then, by the time you got the mold made you could have already printed hundreds of parts on a print farm, so you're losing time too.

That's totally untrue. You clearly do not have any experience designing, building, manufacturing, testing, and certifying either cast metal or PBF parts. BTW, PBF is powerbed fusion and it is how you make 3D printed metal parts. FDM is a plastic manufacturing process and has nothing at all to do with replacing metal castings.

For a certain aircraft part that I designed, that measured approximately 16"x8"x10", if you needed up to 12 of them it was cheapest to 3D print them using powerbed fusion from AlSi10Mg, but with a 25% weight penalty due to the lower mechanical properties of 3D printed aluminum compared to cast. If you needed between 12 and 50 of them, it was cheapest to use 3D printing to make a wax preform then use the preform to make a traditional metal investment casting from A356. For more than 50 of them, it was cheapest to invest in permanent closed die tooling.

Other than for prototyping and extremely low volume production, additive has been a total flop for real-world manufacturing, and has not at all lived up to any of it's lofty promises.

Do you see that changing as parts are designed for additive manufacturing? Things that basically cannot be made another way, but have strength, weight, and even functional benefits over a traditionally made part?

I’m thinking of say cooling channels built into walls of rocket combustion chambers, or car brake/axle assemblies, and some of the „organic“ designs that are lighter and stronger than a cast/machined part.

I wrote FDM instead of additive manufacturing. I'm referring to is actually in SLS (selective laser sintering) space (which is what you refer as PBF?)

What I'm seeing is that companies like Formlabs (plastics) and divergent (metal) are changing the game and you have car parts to car engines to rocket engines being 3d printed.

See my other comment above for more links, but things seem to be changing fast in manufacturing.

Edit:

I think this quote sums the point though:

“With the increased throughput and decreased costs, Fuse X1 has completely changed our perspective on what kinds of projects our lab can support versus what we would have traditionally moved to an injection mold.” Cody Jepsen, Engineering Technician, Additive Manufacturing at Tesla Giga NV

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