[HN Gopher] MIT researchers demonstrate rapid liquid metal 3D pr...
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MIT researchers demonstrate rapid liquid metal 3D printing
technique
Author : Tomte
Score : 83 points
Date : 2024-02-18 07:27 UTC (15 hours ago)
(HTM) web link (www.tctmagazine.com)
(TXT) w3m dump (www.tctmagazine.com)
| amelius wrote:
| How much energy does this use?
| jameshart wrote:
| We know enough from the article to be able to ballpark estimate
| it. Heat capacity of aluminum is 0.9 kJ/kg degC, and the latent
| heat of fusion is 390kJ/kg. The temperature they heat the
| aluminum to is 700degC, from presumably room temperature around
| 20degC - so 0.9*680 + 390 kJ/kg = 1002 kJ/kg is going to be the
| basic heating requirement, or as near as dammit 1MJ/kg. Getting
| that heat into the aluminum and then maintaining that
| temperature during the print presumably introduces some
| inefficiencies (induction furnaces can heat aluminum with about
| 40-50% efficiency), plus they have to move the mass of aluminum
| around with their print motors... but the heat to melt the
| aluminum feels likely to be the main energy sink. Inductively
| heated, with good crucible insulation, 2MJ/kg sounds like a
| reasonable energy budget?
|
| For a comparison, that's about ten times the amount of energy
| you use running your microwave to heat up a ready meal, for
| every kilogram of aluminum you want to form.
| amelius wrote:
| Ok. How much less efficient is this process compared to mass-
| fabrication techniques?
| barelyauser wrote:
| Mass production is not only about energy efficiency. It is
| also about material efficiency and time efficiency. People
| want stuff NOW. Each process has its advantages. 3d
| printing can do stuff that mass fabrication techniques
| can't.
| Qwertious wrote:
| >It is also about material efficiency and time
| efficiency. People want stuff NOW.
|
| Also, if you have a $1M machine then the machine-time
| really adds up.
| barelyauser wrote:
| Precisely. $1M and interest rates of 6% per year mean
| almost $7 per hour just to cover financing.
| gregw2 wrote:
| I wonder if you could just 3D-print a mold and then pour the
| aluminum in as part of a 3d printer like this, rather than use a
| nozzle, and you'd get better quality/resolution.
| amelius wrote:
| Or a 3 step process: PLA mold -> silicone mold -> aluminum
| object.
| jan_Sate wrote:
| I'm thinking about the other way around. Assuming that their
| aluminum 3D printer works, print the aluminum mold using their
| 3D printer. Then make plastic parts with injection molding.
| frognumber wrote:
| Injection molding molds have precision requirements well
| beyond any 3d printing.
|
| They're very expensive for that reason. It's hard even for
| precision machining.
| naasking wrote:
| You can print molds that you literally cannot machine.
| numpad0 wrote:
| But how do you get the product out!?
| lazide wrote:
| You break the mold
| ElevenLathe wrote:
| I've seen hobbyists do investment casting with FDM-printed
| patterns. I assume something similar in spirit is available
| to industry if they want to do it?
| barbegal wrote:
| You can but then you lose some of the advantages of the 3d
| printing technique e.g. the ability to create complex internal
| geometries
| frognumber wrote:
| A 3d-printed mold could actually do that. It'd just be a
| destructive process -- the mold would not survive.
|
| Ceramic is cheap enough that this might be okay.
|
| Removal would be a pain. Probably some chemical which melts
| ceramic but not metal. Perhaps something mechanical which
| relies on ceramic being brittle to break it up. Dunno.
| amelius wrote:
| Silicone is easy to remove.
| twobitshifter wrote:
| You would need a ceramic mold, but that might be easier to 3d
| print?
|
| Right now it is in a bed of fine glass beads that the printer
| drags through as it goes, so this is kind of a similar
| approach. For one offs or prototypes this might be good, but
| when you print more than one of something than a mold likely
| makes more sense.
| frognumber wrote:
| Aluminum sandcasting is what you're looking for.
|
| Sand is cheap, and should be easy to 3d print, even for one-
| offs.
| whatshisface wrote:
| Sand molds have to be compacted.
| rpmisms wrote:
| This is already done using sand casting. However, it's low
| resolution.
| idiotsecant wrote:
| Low resolution is a relative term. It certainly beats this.
| Const-me wrote:
| Here's a commercially available high resolution DLP 3D printer
| people use to make molds for casting gold and silver parts:
| https://www.junction3d.com/
|
| There are downsides, too: printing is slow, and the build area
| is small, furniture parts not gonna fit there.
| unraveller wrote:
| there is a video
|
| https://www.youtube.com/watch?v=H93W-CiOT4A
| mateo1 wrote:
| Cool idea. Impractical but cool.
| frognumber wrote:
| Neat to see this!
|
| As the technology improves, I am skeptical of the necessity of
| sacrificing resolution. I can think of a half-dozen ways to
| improve on this as it moves from V0 to V1 to V2.
|
| The video mentions post-machining, but aside from that, we have:
|
| - More sophisticated media than uniform glass pallets. In
| particular, an outline could be preplaced, so it is more like
| casting. For example, one could have large glass pieces, smaller
| glass pieces, etc. arranged prior.
|
| - Combined methods, where this prints the coarse shape, and
| slower techniques fill in details. This could even be the same
| technique but with successively smaller nozzles.
|
| And simple process improvements (esp. refining nozzle design,
| temperature, and flow rate, so in some ways). I suspect moving
| from liquid to something more like extrusion, could help as well.
| Extrusion can be quite precise. Better process control, with some
| form of feedback loop, would help too. Imaging aluminum in
| realtime through the glass pallets in realtime should not be
| fundamentally hard.
|
| By "not hard," I mean "known engineering process with known
| technologies" (e.g. solvable, but a serious multiyear engineering
| effort).
|
| First press release + video I've seen from MIT which doesn't
| oversell / overhype results or grossly exaggerate potential
| impact. That's refreshing too.
| Animats wrote:
| Wasn't this on HN a few days ago?
|
| There are already good metal printers. They're usually
| sintering systems - put down a powder and fire it in a furnace.
| There are systems for 3D printing sand molds for casting.[1]
| Both of those processes are much more precise than this one.
|
| Metals do usually have a phase in which they're solid, but
| malleable, and can be worked with modest forces. "Modest"
| usually means hammers, large presses, or a rolling mill. A good
| metal extruder working with red-hot but not molten metal would
| need to be able to apply similar forces. That's what the 3D
| printers that work with wire and are similar to welders do.[2]
| There's directed energy deposition, which converts metal powder
| to molten metal for a fraction of a second at the deposition
| point.[3]
|
| This liquid system has the same problem as the 3D printing
| systems for concrete that were being touted a few years ago.
| Some kind of molding or die is needed to guide the material at
| the point the metal becomes a solid, or the result is very
| rough.
|
| [1] https://www.voxeljet.com/3d-printing-solution/sand-casting/
|
| [2] https://www.youtube.com/watch?v=z3nNlVcoba8
|
| [3] https://www.youtube.com/watch?v=oL7bMhPTtDI
| massifist wrote:
| Here's an older HN link from an MIT article.
|
| https://news.ycombinator.com/item?id=39156463
| JoeAltmaier wrote:
| Lots of progress, still clearly many improvements possible. Baby
| steps! This could be very useful in a lunar colony, quickly
| smelting parts and structures out of the lunar soil. It's around
| 8% aluminum (bauxite) which melts at a reasonable temperature.
| Strong enough for larger-scale building uses such as airlocks and
| beams.
| LargeTomato wrote:
| It is a shame we're seeing a divestment in 3D printing
| technologies. Relativity Space recently descoped their entire 3D
| printing department, but I believe they still may be using some
| commercially-acquired printers.
|
| I hope we can see someone else take up the mantle on complex 3D
| printing manufacturing. There's an Indian space company that is
| trying to do what Relativity did. I hope it works out for them.
| nickpinkston wrote:
| I thought Relativity Space pulled back on their use of 3D
| printing for the major fuselage parts, saving it more for the
| engine components, etc., which SpaceX was already doing.
| LargeTomato wrote:
| I believe you are correct. Relativity is now only printing
| engines, just like SpaceX, Rocket Lab, Astra, Firefly, Stoke,
| and others. They are no longer a company driving forward 3D
| printing technology and that's too bad.
| bbarn wrote:
| It's been amazing to watch the 3D printing space grow as far as
| it has. In just the last 10-20 years it's gone from something
| only dedicated people were able to build and get reasonable
| results to high precision devices any hobbyist can get their
| hands on for a few hundred bucks.
|
| I have two resin printers and a PLA printer and I never
| expected at-home capability to get this far this fast.
|
| But, that's still all effectively plastic we're talking about.
| I think the problem with metals is still well.. metals. The
| same types of metallurgy needed for 3D printing have been
| researched and hit almost a dead end with injection molding (I
| know there are some metal injection molding systems out there,
| but it's not hit anywhere near the strength of machined steel
| yet)
| ok123456 wrote:
| People are 3d printing metal right now with LPBF, DED, and
| Wire EDM. For LPBF the challenge is controlling keyholing and
| lack of fusion defects through the process parameters.
| thimkerbell wrote:
| BBarn, how far along are the circularity tools, can I turn
| clean used plastic jugs back into feedstock worth using to
| make 3D stuff?
| ThrowawayTestr wrote:
| There are many designs for DIY filament makers that use 2L
| pop bottles.
| thimkerbell wrote:
| Which kinds of plastic are reusable as filament?
| evilduck wrote:
| HDPE and PET are the most common I've seen in the
| community, which probably accounts for the majority of
| beverage containers you've ever encountered.
| evilduck wrote:
| Something like a PET milk jug is harder since you'd need to
| shred it and remelt a good portion of the jug into filament
| since the handle area would be hard to deal with, which is
| hard to do in a DIY manner. Same for reprocessing failed
| prints and scrap support pieces of prints, plus various
| coloring agents and manufacturer additives make a blend of
| recycled bits inconsistent. It's probably easier to DIY a
| high temp composter than to recycle PLA.
|
| But there's a ton of people out there with jig designs to
| spiral cut a normal cylindrical bottle and feed it into a
| hotend that creates filament from it. Here's one example
| https://www.printables.com/model/768657-petalot-plastic-
| bott.... YouTube has dozens of videos of these in action.
| Generally speaking you won't get as good of results as
| commercial filament since filament diameter needs to be
| carefully controlled and it affects flow rate which then
| affects resulting print quality. If you print something
| simple, large, and practical it's fine, if you need
| something finely detailed it can be fiddly.
| projektfu wrote:
| What class of fabricated metal does it compare to? Cast metal? I
| didn't see it in the article.
| SmokeyHamster wrote:
| This was posted before. Not really 3d printing. It's more of a
| quick casted mold maker, since it just uses a conventional CNC
| machine to "draw" the shape in sand and then it pours molten
| metal in the sand mold.
|
| A clever enough idea, but the results are mixed. It's limited to
| fairly simple 2d shapes and the quality of the "prints" are quite
| poor and require a lot more post processing than true 3d metal
| printers.
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