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Post by anonymous on Jun 2, 2019 6:49:02 GMT
How can additive manufacturing work for metals in orbit? The only way that I know of to "3D print" metals is with a power bed, but this requires gravity to keep the power flat on the base plate. I don't think that liquefying metal and printing it the same way as melted plastic filament is viable but I might be wrong. I found some mentions of it on Google but no explicit explanation of how it works.
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Post by bigbombr on Jun 2, 2019 7:03:19 GMT
It might work through simple cohesion? I got the impression droplets of liquid metal tend to stick to each other pretty well, at least in the case of mercury and lead-bismuth eutectic.
So, print on some kind of surface, the liquid metal cools and solidifies, add the next layer of droplets on the cooled printed metal, wait until it cools, rinse and repeat.
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Post by airc777 on Jun 2, 2019 15:33:02 GMT
Centrifugal force will be plenty to keep the powder bed together. Spin the entire orbital factory slowly.
In the absence of oxidation similar metals tend to bond with each other pretty regularly, so I'd imagine it's not to hard the get a fresh layer of semi molten metal to forge weld to a already cooling layer beneath it. If anything that will be easier in space.
Tantalum Hafnium Carbide has the melting point to be used as a nozzle for applying a molten Osmium filament if you wanted, I see no mechanical reason why you couldn't print most metals.
This is admittedly a bit outside my area of expertise. Professionally I've only worked with subtractive milling machines not additive printers, and I've only done blacksmithing as a hobby.
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Post by anonymous on Jun 2, 2019 23:43:25 GMT
It might work through simple cohesion? I got the impression droplets of liquid metal tend to stick to each other pretty well, at least in the case of mercury and lead-bismuth eutectic. So, print on some kind of surface, the liquid metal cools and solidifies, add the next layer of droplets on the cooled printed metal, wait until it cools, rinse and repeat. How come we use powders and lasers for metal additive manufacturing instead of this on Earth, then?
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Post by anonymous on Jun 2, 2019 23:47:00 GMT
Centrifugal force will be plenty to keep the powder bed together. Spin the entire orbital factory slowly. In the absence of oxidation similar metals tend to bond with each other pretty regularly, so I'd imagine it's not to hard the get a fresh layer of semi molten metal to forge weld to a already cooling layer beneath it. If anything that will be easier in space. Tantalum Hafnium Carbide has the melting point to be used as a nozzle for applying a molten Osmium filament if you wanted, I see no mechanical reason why you couldn't print most metals. This is admittedly a bit outside my area of expertise. Professionally I've only worked with subtractive milling machines not additive printers, and I've only done blacksmithing as a hobby. D'oh! Of course, just rotate the whole assembly. Why didn't I think of that? Wouldn't cold welding cause the powder bed to solidify into an inseparable block, though? I was thinking of additive manufacturing in an environment with some atmosphere like the ISS but that obviously doesn't make sense for large-scale projects like printing an entire space station hull as a monolithic metal structure.
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Post by AtomHeartDragon on Jun 2, 2019 23:47:16 GMT
Centrifugal force will be plenty to keep the powder bed together. Spin the entire orbital factory slowly. This. Gravity has this nice property that if you really need it, you can just make some.
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Post by airc777 on Jun 3, 2019 12:27:28 GMT
Wouldn't cold welding cause the powder bed to solidify into an inseparable block, though? I was thinking of additive manufacturing in an environment with some atmosphere like the ISS but that obviously doesn't make sense for large-scale projects like printing an entire space station hull as a monolithic metal structure. True, fair point.
New proposal: Use welders. Welding machines are additive manufacturing that use metal filaments. Welding machines get around the oxidation layer problem by spraying inert gas on the work surface, typically argon. A robotic arm holding a welder just is a metal 3d printer.
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Post by bigbombr on Jun 4, 2019 9:49:37 GMT
It might work through simple cohesion? I got the impression droplets of liquid metal tend to stick to each other pretty well, at least in the case of mercury and lead-bismuth eutectic. So, print on some kind of surface, the liquid metal cools and solidifies, add the next layer of droplets on the cooled printed metal, wait until it cools, rinse and repeat. How come we use powders and lasers for metal additive manufacturing instead of this on Earth, then? To avoid having to deal with high temperature liquids. Additive manufacturing is often used for small scale applications, as this is where the technology really shines as more conventional manufacturing methods tend to outperform it for cost and speed on larger scales. Small scale means you probably don't want large vats of molten metal.
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Post by airc777 on Jun 4, 2019 10:47:14 GMT
What bigbomber said in the above post. Also you'd still probably have to reheat and harden and then temper the entire work piece after your done if you have very specific tolerances for hardness and uniformity and pretensioning and the crystal structure and such. Modern structural engineering holds modern metallurgy to very high standards, and I'd imagine if your design is shaving grams off of a several kilotons rocket to maximize delta V you're going to have the strictest of material tolerances.
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Post by AtomHeartDragon on Jun 5, 2019 7:46:43 GMT
Wouldn't cold welding cause the powder bed to solidify into an inseparable block, though? I was thinking of additive manufacturing in an environment with some atmosphere like the ISS but that obviously doesn't make sense for large-scale projects like printing an entire space station hull as a monolithic metal structure. You can make large inflatable spaces filled with any atmosphere you can produce, at just enough pressure for your needs. But for powder metallurgy pre-incubating your powder in oxidizing or otherwise reactive atmosphere might be enough if cold welding actually becomes a problem at timescales involved.
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Post by anonymous on Jun 5, 2019 20:40:44 GMT
Let's say for the sake of argument that we want to construct a Saturn V in orbit with only additive manufacturing. What exactly would this orbital facility look like, and how would it work? Wouldn't cold welding cause the powder bed to solidify into an inseparable block, though? I was thinking of additive manufacturing in an environment with some atmosphere like the ISS but that obviously doesn't make sense for large-scale projects like printing an entire space station hull as a monolithic metal structure. You can make large inflatable spaces filled with any atmosphere you can produce, at just enough pressure for your needs. But for powder metallurgy pre-incubating your powder in oxidizing or otherwise reactive atmosphere might be enough if cold welding actually becomes a problem at timescales involved. I'm not sure I understand the oxidized-powder cold welding process.
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Post by airc777 on Jun 5, 2019 22:55:05 GMT
Let's say for the sake of argument that we want to construct a Saturn V in orbit with only additive manufacturing. What exactly would this orbital facility look like, and how would it work? Well, assuming an unlimited amount of money: A space elevator or an orbital ring lifting prefabricated sections and assembling via welders in orbit. Or if the resources for the construction process are being brought from space instead of planet side then magneto plasma dynamic thruster tugs moving containers of material from the moon or asteroid mining colony to your orbital manufacturing center, which from the outside would probably look like a von Braun wheel the size of New York City. The Saturn V was big, like 6.5 million pounds big. The International Space Station is only 925 thousand pounds, and it was assembled in sections all over the world. You can make large inflatable spaces filled with any atmosphere you can produce, at just enough pressure for your needs. But for powder metallurgy pre-incubating your powder in oxidizing or otherwise reactive atmosphere might be enough if cold welding actually becomes a problem at timescales involved. I'm not sure I understand the oxidized-powder cold welding process. Forming an Oxide layer on the powder is to prevent cold welding. In the absence of air similar metals tend to bond pretty regularly without any extra help. If your desired construction material is a powderised metal and you want it to not stick to itself until your ready then you're probably going to want to oxidize the surface. Leaving it in oxygen for a while ought to be enough.
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Post by AtomHeartDragon on Jun 6, 2019 11:58:24 GMT
I'm not sure I understand the oxidized-powder cold welding process. Forming an Oxide layer on the powder is to prevent cold welding. In the absence of air similar metals tend to bond pretty regularly without any extra help. If your desired construction material is a powderised metal and you want it to not stick to itself until your ready then you're probably going to want to oxidize the surface. Leaving it in oxygen for a while ought to be enough.In some cases you might just vent minute amounts of desired atmosphere through your material, depending on whether loses from open cycle are bigger than the costs of making a closed cycle facility recycling unused gases. Anyway, I'm not sure how fast would be powder cold welding in vacuum. If it took much longer than your additive manufacturing then it wouldn't necessarily be much of a problem.
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Post by anonymous on Jun 6, 2019 17:30:48 GMT
Anyway, I'm not sure how fast would be powder cold welding in vacuum. If it took much longer than your additive manufacturing then it wouldn't necessarily be much of a problem. I think the idea is that the metal is in oxidized powder form so that it DOESN'T cold weld into one solid chunk, and to use conventional method of using lasers to melt that powder into a monolithic component (like a rocket nozzle with cooling loops built in directly to the structure rather than bolted on). I'm still having trouble seeing any of this being used on a large scale, even though it would be very useful.
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Post by AtomHeartDragon on Jun 6, 2019 18:10:54 GMT
Anyway, I'm not sure how fast would be powder cold welding in vacuum. If it took much longer than your additive manufacturing then it wouldn't necessarily be much of a problem. I think the idea is that the metal is in oxidized powder form so that it DOESN'T cold weld into one solid chunk Yes.
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