[HN Gopher] Low-Temperature Additive Manufacturing of Glass
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Low-Temperature Additive Manufacturing of Glass
Author : LorenDB
Score : 97 points
Date : 2025-06-18 16:13 UTC (4 days ago)
(HTM) web link (www.ll.mit.edu)
(TXT) w3m dump (www.ll.mit.edu)
| jiehong wrote:
| Very cool indeed!
| giantg2 wrote:
| Interesting. I wonder if this could be used to print telescope
| mirrors if you could get an "ink" that has high thermal
| stability, or if that would be in conflict with the low
| temperature printing.
| hbrav wrote:
| That seems like it would be very difficult. For a telescope
| mirror you want a very good surface finish, and that's one
| thing that 3D printing does very poorly.
| giantg2 wrote:
| The polishing process could be done differently. If you could
| print the specific parabolic shape, that could save a lot of
| time hogging out. Although slumping might work better if
| surface ends up smoother. Im not sure of the annealing
| process might go.
| taneq wrote:
| There's a few combined-process setups coming out these days
| that use 3D printing as a first pass and then machine the
| print in-place before sintering etc. which saves a ton of
| setup and fixturing time.
| sheepscreek wrote:
| Yes! This is exactly what I had in mind. Sintering
| (thanks for the term) combined with this 3D printing
| technique could still make the process faster and lead to
| more consistent results.
|
| Now that's I think about it, one could in theory use the
| exact same process for plastic-polymer lenses too, albeit
| at lower temperatures (better).
| bhickey wrote:
| The parabola of a telescope mirror generally deviates from
| a sphere by tens of micrometers at best. Figuring happens
| after grinding and after polishing. Slumping is neat, but
| I've heard from the grognards that they can shatter if the
| temperature changes too quickly.
| sheepscreek wrote:
| Maybe with further augmentation to the process. The 3D printing
| seems to leave pretty big grooves on the glass - which can
| distort the passage of light. For any real optical application,
| that will have to be removed somehow. Such as baking the glass
| structure in a high heat oven with a centrifuge/fast spinning
| base and some kind of mould to put the initial piece on.
|
| The high heat and spin action could, in theory, fuse the
| individual grooves for a more uniform dispersion of light, and
| the mould shape would further press on the glass to maintain or
| alter its shape to be closer to a lens.
|
| Finish that off with fine "sanding" and/or polish, and that
| might do the trick?
|
| Honestly, experimentation might be the only way to find out.
| kragen wrote:
| You'll probably be interested in
| https://dercuano.github.io/notes/gradient-refractive-
| index.h..., which isn't exactly what you described.
| metalman wrote:
| this is a highly missleading "anouncement" about sodium silicate
| "glass"(ish),stuff
|
| https://en.wikipedia.org/wiki/Water_glass
|
| but if you want to plqy with some, it is readily avail8ble as a
| "cement" used for attaching seals to wood stove doors, and
| countless other low teck applications the comon name of "water
| glass" refers to it's solubility, so.....
| bahmboo wrote:
| That's not what this is. Sodium silicate is part of the process
| but so are lots of other things. The patent is posted here in
| the comments that would be a good place to start if one wanted
| to experiment with it.
| gsf_emergency_2 wrote:
| https://patents.google.com/patent/US11499234B2/en
|
| I wonder what the other inorganics ("functional additive,
| embodied in some cases by Silver flakes") are, exactly. In their
| flagship product.
|
| And the size of the nozzle, why not the easier to remember 400
| micrometers?
| ricardobeat wrote:
| What do you mean about the nozzle? They describe it in microns:
|
| > The ink can be extruded through a nozzle 604 (e.g., a 200 mm,
| luer-lock tapered nozzle)
| kragen wrote:
| So it sounds like a single-component process, no powder bed or
| vat of hardener liquid. "Silicate solution" presumably means
| waterglass rather than something like tetraethyl orthosilicate,
| and if it hardens rather than foaming up at 250deg, it's either
| because they're doing the process under pressure or, more likely,
| the other inorganics they mention are donating polyvalent cations
| such as Ca++, Mg++, Al3+, or Fe3+ to crosslink the silicate
| residues.
|
| Probably the polyvalent cations are bound up in a salt that has
| negligible solubility at room temperature, so the ink doesn't
| harden in the reservoir, but which can react with the silicate at
| 250deg, maybe a hydroxide or carbonate. Calcium sulfate is
| probably too soluble.
|
| Presumably the silica filler is amorphous and serves to
| strengthen the glass and reduce the TCE, though it probably
| raises the cost. Maybe it also makes the paste thixotropic
| without needing to include organics like carboxymethylcellulose
| which would be hard to remove later. And I guess maybe it could
| react directly with the waterglass to solidify it, in effect
| raising the waterglass's modulus out of the water-soluble region,
| without requiring any polyvalent cations. Silica fume is the most
| likely form of silica here.
|
| If anyone digs up more details, I'd love to see them.
|
| Hmm, I see gsf_emergency_2 found this patent from 02020:
| https://patents.google.com/patent/US11499234B2/en which is later
| than Dercuano but earlier than Derctuo and Dernocua. But its
| priority date is from a provisional patent application from
| 02019, so even Dercuano doesn't count as prior art, even if it
| anticipates some of the claims. Also, though, I don't see
| anything that anticipates this process in notes like
| https://dercuano.github.io/notes/flux-deposition.html and
| https://dercuano.github.io/notes/powder-bed-3d-printing.html,
| which suggests that it wasn't as obvious as it sounds.
|
| The patent says, "curing the material to evolve gaseous water,"
| which makes it sound like thick sections _would_ foam up. (You
| have to heat it over a length of time quadratic in section
| thickness to permit water to diffuse through the nascent solid.)
| And supposedly that is the purpose of the heating, rather than
| provoking the other reactions I speculated about above.
|
| There are some interesting notes in the patent about promising
| functional fillers, such as carbon fiber for strength or silver
| flakes or conductivity. It suggests using these inert fillers at
| loadings of 45% to 90%.
|
| It confirms that the silica is fumed silica, and suggests as
| alternatives fumed alumina (sapphire) or fumed titania (rutile or
| anatase), which are not products I had heard of, though titania
| nanoparticles are common as a white pigment in paint and in food.
| Waterglass can definitely crosslink with aluminate sources such
| as metakaolin, as used in "geopolymer cement". Titanate is news
| to me, if true.
|
| It also confirms my inference that the fumed silica makes the ink
| thixotropic, at 15 wt%, though it uses the phrasing, "introduces
| a yield stress into the material" and "shear-thinning behavior".
|
| I'm definitely going to use that phrase the next time I'm making
| mayonnaise.
|
| "Why are you stirring that bowl of egg yolks and oil with a
| fork?"
|
| "I'm introducing a yield stress into the material!"
|
| The patent also confirms my inference that the silicate solution
| is waterglass; it specifically says sodium silicate (or ammonium
| silicate, which is probably not a practical possibility:
| http://www.sciencemadness.org/talk/viewthread.php?tid=10297)
|
| The patent doesn't suggest using ionotropic gelation in the way I
| suggested at all. It doesn't mention the mineral oil either.
| MonkeyClub wrote:
| > from 02020
|
| Is the year in octal (/s), or do you truly believe we're due to
| survive eight more millennia with the same year numbering
| system?
| nemomarx wrote:
| I think the long now foundation tries to promote it to raise
| awareness and get people thinking about the future
| consequences of things.
|
| It seems very optimistic and 90s to me now
| jagged-chisel wrote:
| https://news.ycombinator.com/item?id=43613664
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