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Comment by jpgvm | Hacker News Reader

That price was for essentially CNC milled prototypes, I imagine if they cast them they would be a fraction of that price.

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They could offer very customized versions made in an Inconel 3d printer.. Wonder if that (economically & technologically - is inconel seawater safe??) really makes sense, though.

You can use direct metal laser sintering on most powered steels, no need to use Inconel. The reason it's often used with Inconel are the parts you want to make from Inconel are difficult shapes to cast and milling Inconel sucks, eats tools for breakfast.

casting that shape would require some kind of sacrificial mold like a sand-casting process. cheaper than billet, but not by much unless you're talking big industry scale.

I wonder myself if it's small enough to use a laser-sintering print process to build.

Sacrificial sand moulding is done all the time and is pretty cheap:

https://youtu.be/lnHhP_kZ43k

If the two halves of a mold have some helicity, I suspect it is possible to cast such a shape. After all, the water also needs to flow through the prop, so too can the halves of a mold.

Even if the geometry doesn't quite work out, it's also possible you could cast a shape that can be "unscrewed" from the mould and then machine a relatively thin layer from the outside of the cast part (relative to how much you have to machine from a billet). It'll need some level of machining anyway.

Binder-jet printing of sand cores is pretty cool too.

Why would you cast it at all, when it's a perfect shape for forging the blades and then welding or brazing them (depending on the material) to a central hub?

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