[theelous3]

Lead is a nightmare to machine. It's gummy. You'd think aluminum was easy because it's softer than steels, but that comes with it's own challenges. Lead is worse so. You're right that this isn't so bad on a lathe as opposed to a mill or (lol) a grinder, but you're not going to see a need for a lot of solid round shielding.

A little bit of lead in steel will increase machinability, but only a teeny amount. Similar to adding a small bit of phosphorus.

It's also hard to hit dimensions in lead, and if you do hit them, the second the temperature changes you'll lose them. Additionally, whatever you make can't see any stress, or the part is donezo.

Idk if you've ever handled lead - but considering you can bend thick sheets of it by hand and melt it on your stove, I'm sure you can imagine the kind of issues you might have integrating expensively machined chunks of it in to hot high pressure environments with moving parts.

Even though lead is cheap and this filament is expensive, actually getting the lead to shape by machining or working it is also a costly process. 3d printing has a sort of cost ceiling. Once a part is designed, all of the real work is done. For fabrication and machining - once the part is designed the work has only begun.

What might look like a small and simple combination of geometric shapes can cost thousands to machine.

I'd rather spend 500 on filament and a day's engineering labor on a part than the same day's engineering, 100$ of lead, and 1k or more on manufacturing. Not to mention the lead times on machined parts can be wild.

[kragen]

i think all the post-manufacturing problems you describe with lead — dimensional instability, thermal creep, plastic deformation, incompatibility with hot high pressure environments, vulnerability to wear — are even worse with this filament

maybe an exception is that petg's maximum elastic strain is larger than lead's

[theelous3]

Considering lead's modulus of elasticity is essentially zero, yes :) You can drill, tap, and generally rely on this material to stay in the shape it was printed at in maaaaaany more situations than lead.

Of course the petg in there is a limiting factor, but even plain petg is an order of magnitude better than lead at retaining its shape under a wide range of loads. You can print gears for lathes in petg! And they last years! (If you're wondering why you might do this - it's a good idea to have a cheap point of failure on devices that have enough power to rip themselves to shreads.)

Not to mention this is only v1 of the material. We could see exotic plastics that are far more heat resistant like PEEK get a secondary filler for niche radioactive usecases.

[kragen]

https://www.matweb.com/search/DataSheet.aspx?MatGUID=ebd6d2c... says lead's modulus of elasticity is 14 gigapascals and https://www.matweb.com/search/datasheet.aspx?MatGUID=cb9580a... lists one variety of petg as having a modulus of elasticity of 2.2 gigapascals; i think you are confusing your material properties with one another

(at such low filler loadings the tungsten will change the modulus of elasticity very little)

petg does have higher yield stress than pure lead (53 megapascals vs. what https://nickelinstitute.org/media/1771/propertiesofsomemetal... says is 17 megapascals) but there are lead alloys that are in the same range of yield stress, including regular lead-tin solder. but they won't last if you try to make change gears out of them precisely because they're harder than petg

by the same token, though, i think you're going to get a lot of springback and long-term distortion out of petg you aren't going to get with lead