Printing with metal

Anyone do any thinking or progress on making a head for 3D printing of metal objects? Seems to me that metal flows much easier than plastic, so it ought to be able to print finer detail than plastic. Some metals aren't to bad heat wise. Aluminum for example, should be a possibility.

It may be necessary to have a gas filled tent to prevent oxidation. Something like Argon or Helium. I think they use Argon for MIG welders. With a simple tent, we could have very little leakage. That would also keep the air clean for the people as well.

Tony

There is a RepRap metal extruder but it is designed for putting Field's metal into plasic grooves.

Metals go from solid to liquid. They don't have a paste like phase in between like plastics do. That means you have to pour them into someting rather than building up layers freeform.

I think there is a technique using a MIG welder and a robot arm.

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[www.hydraraptor.blogspot.com]

Ant said:
"Some metals aren't to bad heat wise. Aluminum for example, should be a possibility"

I melt Aluminum in a crucible in a charcoal furnace. I put some of the different plastics into the melted aluminum. Guess what! The all returned to their basic carbon base structure. That of black carbon. This is defiantly not the way to create wires inside of plastic. Aluminum in the molten state is about 1100 F or around that temp.

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Bob Teeter
"What Box?"

There was discussion in a thread about a powdered metal (bronze maybe?) that is suspended into a sacrificial paste like substance that can be printed and then fired in a ceramics kiln to solidify the metal. I searched briefly for the thread but did not find it.

This of course would prevent the embedding of this metal into plastic parts because they would melt and turn to carbon during the kiln firing. At this time I do not thing the technology exist to print molten metals into plastic parts for things like wire traces and the like.

What is possible though is an attachment that would lay some solid copper strand down ahead of the printing head. The print head would then continue to extrude plastic on top of the wire, permanently sealing the copper wire within the part. Simple motor and coil winding wire found at any hobby shop could suffice. I have sevral spools ranging from 36ga all the way down to 16ga. You can pick up a 3 pack with very thin (forgot the ga might be 30ga) to 18gauge at radio shack for under $5 bucks. You could even reclaim the thin ga from small transformer coils found in most broken vcr, radio, and other electronics that step household voltage down to electronics level voltages.

Another thing that could be used is graphite impregnated plastic that would lay down a conductive line of plastic. The bad thing is that in my limited experiences graphite has a high resistance and gets quite warm when current is passed through it.

These guys rapid prototype their positives to be invested and cast. It's a couple extra steps but shouldn't the RepRap work for this without any modifications? I'm not sure how well the different plastics would burn out of the investment though. It would be nice to be able to print wax for this purpose but wax expands and contracts tremendously with changes in temperature so it may not be practical.

I also found this link although I don't know any details about it.

I would love to be able to create an exact replica human skull in either stainless steel or titanium. Looks like I'll be waiting a while for now though.

Seems like wax turns into a liquid too, so it might work really well. Turning into a liquid is a big advantage. It'll cool instantly when it touches solid material, so paste like mode isn't necessary. Wax also has an advantage that it could be extruded under water, and that'd allow the water to sustain the weight of it... sort of. 1100 degrees doesn't scare me in the slightest. In fact, it is quite easy. As long as there are plenty of materials that can take the temperature, it is easy.

Tony

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It'll cool instantly when it touches solid material, so paste like mode isn't necessary.

Nothing cools instantly, and if it did it would not weld to the layer below. I doubt whether there is a temperature and flow rate that could be used to build an accurate object from molten metal but it's worth a quick try.

I would think wax extruded under water would behave a bit like pillow lava extruded under the sea.

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[www.hydraraptor.blogspot.com]

FYI, it is /possible/ to do freeform deposition processes with metals. CMU does it all the time in their shape deposition manufacturing processes. In order to get anything even remotely like a reasonable surface finish they machine it afterwards...

[www.cs.cmu.edu]

This does, on the other hand, let them make parts that you just can't do by normal machining, and brings the complexity of going from solid model to machine instructions to only a little bit more complex than running our machine, as they can avoid all clearance problems with their end mills by just not having anything it could interfere with present when doing the machining..

Incidentally, the work on SDM is also why I'm interested in being able to do very light machining on a RepRap - You can go quite slowly and still get work done if all you're doing is removing the outer .5mm of the part to put a good surface finish on it.

Yes that is the MIG process I was referring to. I don't think you can simply pour molten metal as it will flow away before it sets.

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[www.hydraraptor.blogspot.com]

Cool. Thanks for the link! I agree, machining is very important. I'm working on one that'll do machining with small cutters.

Tony