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MetalArc: A Low-Cost Metal 3D Printer

A 3D printer based on a MIG welder

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Project Status: Built and testing

Not long ago a professor drew my attention to a project done by the Michigan Technological University. They had taken a welder and stuck it above an inverted delta printer frame. Then they where able to effectively print a part out of metal. I had some serious doubts about this method (just like when I first saw ABS FDM 10 years ago). But instead of just scoffing at the project I figured why not give it a go and who knows what can happen.

The project uses an Aluminum frame design to keep all of the heat sensitive components away from the high temperature zone of the welding. The controller is connected to the switch input of the welder and can turn the welder on and off. The feedrate of the welder can not yet be adjusted from the controller.

This project is intended for testing and getting input from the community. I have some serious doubts about using a MIG welder for a 3D printer but who knows, what an adventure!

The 3D printer is made using the following components

  • An frame using aluminum extrusion, timing belts and stepper motors. Loosely based on http://openbuilds.org/
  • A SlushEngine controller (no plug intended, its just the most convenient controller)
  • Linclon MIG welder (140c)
  • Some metal plates to weld on to

  • Impatience lead to a bad first print

    roboteurs11/14/2016 at 16:37 0 comments

    The first print I did with this printer was just bad. And the reason is I couldn't wait for the shielding gas to show up. From the beginning I intended to use the smallest welding wire possible (0.020). But I didn't have that on hand or the shielding gas when I go the machine together for the first time.

    In my impatience I decided to try a print using (0.035) MIG Flux-core wire. That was a mistake.

    The current required to melt this wire and deposit a the rate I needed kept tripping the breaker. Also my feed rates where to high so the weld kept skipping ahead of its self.

    As you can see it was just a mess.

    Another lesson learned from this experiment is that 14Ga steel is not thick enough to print on to. The plate warped like crazy. I have done some work on the very big and fancy 1.5 Million dollar machines and they print onto a 1 inch steel plate to prevent warpage. I guess I need a thicker plate :S

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Jerry Biehler wrote 11/16/2016 at 22:19 point

you would have to put a D.C. Clamp meter on it to see what the current draw. But these are rated at 20% at 90A. What size wire are you running

  Are you sure? yes | no

roboteurs wrote 11/16/2016 at 22:24 point

I will be using 0.020. When I tested it before it was pulling about 35A. But i will probably need more because the weld deposit wasnt great.

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roboteurs wrote 11/16/2016 at 22:24 point

Lots and lots of testing still to do.

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Jerry Biehler wrote 11/16/2016 at 23:09 point

You mean .023? 35 amps is really low for that. I don't think your weld parameters are anywhere close to what they should be. 

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Joni wrote 11/16/2016 at 09:38 point

At Cranfield we've been playing with this as well.

http://waammat.com/

Lots of papers published.  We've been using rolling afterwards to try to normalise the grain structure in the metal.  We now also have the worlds largest 3D printed metal part!

http://waammat.com/blog/have-we-3d-printed-the-biggest-metal-part-ever

It's important to get it suitable for aerospace because we have a massive ratio between the size of the metal we buy and the actual volume of the finished part.  If we can reduce that then there is less environmental impact and everyone is happier.

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roboteurs wrote 11/16/2016 at 22:11 point

Thats very interesting. looks like you guys are miles ahead of what I am doing. I will continue to examine these papers as the project continues. Still waiting on Argon at the moment....

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Joni wrote 11/17/2016 at 15:58 point

Maybe but it uses a very expensive robot to do the work. Do consider whether you can use post pass rolling. It really improves the fracture toughness of the finished piece.

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Jarrett wrote 11/17/2016 at 17:52 point

What is post pass rolling? I'm not a welder, but this sounds important.

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Joni wrote 11/17/2016 at 20:41 point

Post pass rolling is when you apply high pressure via a roller to the bead you just laid down.  The crystal structure of the metal from the weld is quite directional and has a lot of large crystals.  This means it has low fracture toughness and is not the same strength in all directions.  The post pass rolling causes the grain structure to recrystalise as smaller equiaxed grains which gives you much better material performance.  The affect is similar to what you get in annealing a piece of metal.

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Jerry Biehler wrote 11/16/2016 at 00:55 point

Dont forget, those little machines only have a 20% duty cycle. Thats 2 minutes on and 8 minutes off. Other wise the best case scenario is the internal thermostat will trip, worst case, you fry the transformer. (I used to be a welding service tech)

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roboteurs wrote 11/16/2016 at 22:13 point

Right now it is pausing after every layer for a while. This also helps some of the heat leave the part. To be honest I wasnt thinking about the health of the welder when I wrote the software :S. 

If we are on a very low heat is this duty cycle still applicable? The thin wire doesn't require much heat to deposit.

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