

Open-source metal 3D printer - emrgx
http://www.appropedia.org/Open-source_metal_3-D_printer

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TehCorwiz
Sadly I can't find any images or videos of the product of the device. The site
has a couple of videos showing it throwing sparks, but that's about it.

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claar
Agreed -- the fact that they don't show a single finished item tells me that
the quality of the printed part must be _extremely_ bad.

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Animats
It _is_ extremely bad. See the actual paper, where they show one part and its
CAD model.

[http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6678...](http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6678531)

There's only a vague resemblance between model and part. No way could you use
that sprocket. Not only are the edges rough, it has voids. You could grind or
machine down down rough edges, but voids make the process worthless even for
making blanks. That's about what you'd expect with MIG welding. Welding just
isn't a good way to make smooth surfaces.

The low-end 3D printer people tend to obsess on the problems of building a
3-axis motion system (a completely solved problem in CNC machines) and gloss
over the problems of what's happening at the weld point. The common extruder-
type printers are trying to weld a hot thing to a cold thing, which never
works very well. (In soldering, that creates cold solder joints. In welding,
it creates bad welds.) Heating the bed plate helps a little, but once the
thing being built is more than a few cm high, the build plate isn't
accomplishing much. That's why most taller objects made with low-end 3D
printers fail.

There's a plastic welding technique that's been in use since the 1950s that
works reliably.
([http://www.professionalplastics.com/WELDER](http://www.professionalplastics.com/WELDER)).
Not only is the welding rod heated, the target area is heated with hot air.
This produces a solid, reliable weld. I've suggested doing something similar
for extruder-type 3D printers, using small lasers (2-5 watts) to preheat the
target area just ahead of the extruder. So far nobody has done that.

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merrillii
Heating things with a laser is not quite as easy as you might think. Different
materials will absorb different wavelengths of light at different rates. So
for example a 1um laser might not heat white polyethylene enough while it
would melt black ABS. Hot air has the advantage that it is always a consistent
temperature regardless of the material.

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Animats
Use a laser diode pulsed with pulse width modulation, at perhaps 1KHz, duty
cycle < 80%. During the off period, view the hot area with two photodiodes
behind different-wavelength IR filters. The ratio between the outputs gives
you the temperature. Go closed loop on temperature.

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jeffchuber
It's so cool that it's an inverse delta! Sadly this is probably because they
had to find a way to circumvent patents.

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samatman
Not necessarily. Tilting the substrate platform lets you build more complex
shapes without support material.

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jeffchuber
I have a delta 3d printer and I'm having a hard time imagining how this would
work... Do you have an example?

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samatman
Looking closer, this doesn't apply here. The Stewart platform allows 6 degrees
of freedom, with useful amounts of tilt. The inverted delta used here is 3
axis.

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chuckkir
Additive manufacturing pretty much always needs some sort of leveling phase to
cope with z-axis irregularities. Without that you can't hold tolerance.
Furthermore without support material you're limited in what you can build.

Looking at the pictures this seems like it makes metallic blobs approximating
the shape. I suppose if you have a CNC to post-process it into something
closer that may be fine. It'd be nicer to do the machining on the fly, but
with the width of the material deposition it looks like it would drip down the
sides if you did that.

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rtkwe
With this design you might but you can get good essentially flat layers using
the same essential process. There are existing commercial machines that use
metal welding to do mixed additive and subtractive manufacturing. It's really
a question of getting the welder dialed in so it creates a smooth enough
surface. The weld will also fill into the small inconsistencies in height
better than filament.

[https://www.youtube.com/watch?v=s9IdZ2pI5dA](https://www.youtube.com/watch?v=s9IdZ2pI5dA)

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tehzorroness
Perhaps manufacturing processes like laser sintering or 3D printing with a MIG
welder have not become mainstream because traditional metalworking processes
like casting, turning, and milling are so much faster and much more
repeatable. Let me know when this thing can hold tolerances of +/\- 0.0001".
We'll probably have a cure for cancer by then.

Metal can be a tricky material to work with. It takes a lot of force
manipulate. If you don't know what you are doing, you can very easily get
seriously injured or even killed. To me, it would seem much more rational to
try to build low-cost milling and turning centers that are small enough to
move into a house without taking out the walls and simple enough to maintain
where you don't need to have certified mechanics come every time you crash it.
You're still going to have to make a considerable investment of time to learn
how to safely and properly operate it, but that seems much more realistic
scenario than emailing a file to grandma, having her put on her sunglasses,
then pressing "Print," followed by 6 hours of sparks flying.

Don't get me wrong, I'm sure there are applications for additive metal
manufacturing processes, but I believe that the cases where they are the best
solution are few and far between.

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merrillii
I think your bar is a bit high. Standard milling tolerences are almost 50x
higher than what you state. Casting is much worse. The point is that additive
printing won't take over the metal world any time soon but it does have some
advantages. Try to machine a hollow sphere for example. There are plenty of
shapes that can't be traditionally machined.

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Animats
Yes, milling to 0.0001in tolerance is rare, although possible on some
machines. 0.001in is not unusual, though. This 3D printer, from the pictures,
seems to be delivering about 0.2in. That's worse than sand casting. Still
worse, some of the errors are in the void direction, undersize. If this thing
consistently produced a good solid metal blank, ready for finish machining, it
could substitute for having a foundry for small jobs. But it's not even that
good.

There are very good, but expensive 3D printers that print excellent metal
parts. Check out Space-X's 3D printed rocket engine for the new Dragon
spacecraft. Shapeways can now do small steel parts for $10 + $5/cc with
reasonable tolerances. 3D printing of metal works now. This welder thing, not
so much.

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nickpinkston
I'd rather see this used as an robot-welder than a "3D printer". At least
enclose this in an argon chamber dammit!

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RyJones
How about something like SHIP2? They print the shape in the green and compress
it using gas. This allows 3D printing of Inconel in shapes that require almost
no machining after production.

[0] [http://www.summitmaterials.com/near-net-
shape/](http://www.summitmaterials.com/near-net-shape/)

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contingencies
See also [http://minimetalmaker.com/](http://minimetalmaker.com/)

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immaceleb
woah nice

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dustinmoorenet
I have welded before and I know that you need to clean each weld with a wire
brush. I just can't imagine what is created is very strong. We need some
pictures and some stress tests validating it as useful.

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chromaton
They might be able to reduce the oxidation on each layer by enclosing the
whole thing in a box filled with an inert gas. (This is the recommended
technique for welding titanium, for example.)

Argon is relatively cheap.

