MIG weld extruder

This idea only just hit me, regarding the issue of printing in metals. It seems similar to the existing extruder in that it could operate from a spool of material.

With MIG welders fairly common, a test setup would not seem hard to produce. It would need some modification of wire-feed controls however.

Further, it got me wondering if it could be fed with multi-strand wire of different materials to produce different alloys.

It would require a heat-resistant print bed and a sacrificial grounding/seed terminal. But if the terminal were also a wire-feed up through the bed then it would just be a matter of cutting one wire/element to free the printed item.

Beyond this it gets into more metallurgy than I know about, but I am aware that the practice of welding on top of welds can be used to produce hardened surfaces for anvils.

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Peter "Sci" Turpin
London, England

Provider of practical solutions.

(Sometimes stellifying Jupiter IS a practical solution)

I believe that scientists have done this, but the problem is that it cant get anywhere near a consistent line unless the whole thing is in a vacuum. Which makes it more useful to astronauts, who cant just go and buy parts that break. There was a video of it online but i cant seem to find it right now.

It does not have to be in a vacuum the key is to have the atmosphere Inert (no oxygen) It is actually not difficult to manufacture a controlled atmosphere box (a glove box is an example of this) to place the reprap in as everything can be kept at normal atmospheric pressure. The box can be made with plexy and electrical pass through can be sealed with silicone. Argon is probably the best inert gas and if you have a mig welder you already have the argon setup with a regulator you may just need a bigger tank of argon.

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[thejabberwockyandthejubjubbird.blogspot.com]

I find it strange that this hasn't been explored more thoroughly. Controlled atmosphere is no more difficult than making an enclosure. The XYZ axes would need a positioning system which is spatter resistant. Sounds like a job for hydraulics.

Could just put gaiters around the moving parts to keep spatter off them?

Additionally since this would be a positive-pressure setup, all we're talking is putting the machine in a non-flammable box.
Though with heat buildup, would probably want a fan in there to circulate the gas. Possibly even a heat exchanger.

I newly own a cheap china TIG welder and from what I read both MIG and TIG welding use the inert gas not only for preventing corrosion but also for cooling the weld so thin materials don't burn through and using the gas stream to "carry" the plasma so the spark becomes more stable.
So simply filling up a room with argon and weld in it would change the behaviour of the welder completely.

Plus it's a really energy-wasting way of building things. This kills icebears. I don't like it.

Totally depends on what's being built.

If metal is more appropriate, makes sense to do it once in metal than replacing plastic parts for years.

I had this idea. I have done a lot of TIG welding and it is not as difficult as many people make out. I learnt with a book on it and practice.

I also know of engineering firms that use mig welders to build up damaged stainless prop shafts with a lath and the welder rigged to it.

A part from protecting from splatter I really don't see the need to make enclosed chambers. MIG welding steel usually uses CO2 not argon. How detailed or consistent the part will be is another matter but I cant see any reason why it wouldn't work. You will however need a hefty X,Y,Z as the cables to the welding torch are large and stiff. Then you should be able to just clamp a MIG torch on and rig it to switch on and off. It should be that simple to try.

The other option is designing a TIG torch head. This would see the tungsten electrode with ceramic shroud arcing to the metal and the steel wire being fed by a feed system on the head in to one side of the ark. To turn on the ark and gas all you have to do is wire in a switch to do what the one in the handle does. The welding machine controls everything else. You could get more control too as a lot of machines can have additional controls fitted so current can be controlled remotely by a foot peddle. This could be adapted to be automated by a program. This method may be more reliable and smooth but I wouldn't make any bets.

One last note. Very smooth and nice welds are achievable automated welding machines. No enclosed chambers required. It may be possible with a good MIG machine and the right programing to get some surprisingly good results. I don't thing you will get a good resolution but I wouldn't want to be certain about that. If you can get tiny wire and feed it, then set the current accurately, it may be really good.

All the idea needs is the right person or persons.

Well NASA has been working with electron beam FFF.



A key problem that I see with printing metal is that, if you intend to produce structural parts, you have to be really confident about the strength of your parts. That seems to be what nasa is focusing on with their studies.

Another issue, at least with their current setup (called EBF^3) is that it can't print structures smaller than 2mm. so at best, you can print a rough part and machine it down to final specs, similar to casting.

Interesting video. They are using the electron beam like a TIG ark. We could just use a TIG ark.

A lot of the time bad welds are because of human error and contamination of the metal. The control of the machine eliminates the human errors of inaccurate arc lengths and erratic feed speeds. Plus if the layer you did before was good then the next layer will be.

I really cant see it being any more difficult to get to work than making plastic parts. A good weld is 100% solid all the way through. It should be as good as you are ever going to get with depositing any material in layers.

Making rough casting like components is extremely useful. If you have ever tried to machine a lump of steal to replace a casting then you know how tedious and hard work it can be to make a big hole or turn a load off. Not to mention wasteful. The machining time saved would be fantastic.

I have so much experience in metal work I can see this working from a mile away. When I finally can get a Mendel kit and get it to work I may rig a simple set up like this in it or on a second machine.

Welding is a really long established practice and even if you have zero experience at it with a good instructional guide book and quality machine rigged up I cant see it being so difficult to get good results. Half the skill of hand welding is learning to hold everything the right distance and move it the right speed and manner. The other half is knowing how to set the equipment and it is not as complicated as a Mendel by far. When movement is automatic it should be a doddle.

BTW a TIG based system could build up in all sorts of metal. Aluminium can be done with a expensive machine but there may be electronic interference issues because it uses AC to stop oxidation building up. But copper, Brass and all types of common steel could be done if suitable wire can be found.

... it's the same with laser-assistet welding - read through the SpoolHead-discussion (especially my posts) : [objects.reprap.org]

Edited 1 time(s). Last edit at 01/31/2011 04:30PM by VDX.

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Viktor
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here's a FAQ about EBF3.

One thing they mention is that their process takes ~6 hours for a solid 15 cm^3 cube, and ~2-3 hours for a hollow cube. How long does a tank of argon last? A benefit of a vacuum is that you don't have to use any gas, and the chamber shields people from the harmful UV. maybe combine the two; displace the air in a vacuum chamber with argon, then pump out the argon to a soft vacuum? the remaining gas should be mainly argon. (the benifits being: you don't use so much argon, it's a soft vacuum so less problems with outgassing and sealing, and the argon might displace the atmospheric gases so you won't have porosity and oxidation problems)

Running a welder for 6 hours probably isn't good for the ol' electric bill, either.

Another thing they mention is that they heat treat all their finished prints to remove internal stresses and bring the parts up to full strength.

Overall, it doesn't seem like a metal printer is going to be feasible for most households. I can see building a business around a metal printer, i.e. printing out engine blocks, heat treating them, and machining them into a finished custom part.

One of the things the lead of the nasa project was saying in a lecture i saw online was that there are many industries drooling over the prospects, and a key reason for the project was to show that there is demand out there for commercial machines. in other words, Boeing would buy one of these printers if someone/anyone was making them.

Edited 1 time(s). Last edit at 01/31/2011 04:48PM by Buback.