
MX3D is to 3D-print a steel bridge over water in Amsterdam - dnetesn
http://phys.org/news/2015-06-mx3d-3d-print-steel-bridge-amsterdam.html
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Animats
Here's the actual process.[1] It's not clear if the video has been sped up.

The product quality seems comparable to rebar. Making a pedestrian bridge out
of that stuff is a stunt, but it could be useful for making rebar reinforcing
over which concrete is then poured. This would be useful for complex concrete
forms.

[1]
[https://www.youtube.com/watch?v=NFF0QQIQDXE](https://www.youtube.com/watch?v=NFF0QQIQDXE)

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kragen
Why "comparable to rebar"? Are you talking about surface finish, or material
properties (which I, at least, am more interested in)? I normally think of
arc-welding-deposited steel as "comparable to an arc furnace", i.e. very high
quality. Could be that they're not using enough gas or something, and so end
up with oxidation at the surface and possibly within the material; I'd like to
see more detail to be sure.

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Animats
I'd like to see more detail too. The video looks like they're tack-welding BB-
sized pellets together.

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PhasmaFelis
There's a photo and a video of two different bridges in different locations,
both about halfway through construction. If you read to the very end of the
article, though, they don't plan to start construction until 2017, and they
haven't even finalized the location yet. Also, it's expected to take two
months of continuous operation to complete.

Seems like they're deceptively frontloading the interesting stuff to drive
traffic.

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skmurphy
If you look at the various elements of a 3D printer--filament/material, print
head, print arm, bed, position control, material transformation model (e.g.
fusing, sintering, curing/hardening, ...) they are innovating in a couple of
dimensions at once. The idea of transporting the printer to the job site and
not being constrained to a small volume by print head and arm seems to offer a
lot of possibilities.

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monk_e_boy
I think this would only be useful for robot/3D printer to do the fiddly bits
of the bridge that are unique to that particular location (either end). Surely
95% of the bridge is cheaper to make in a factory some place?

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skmurphy
A fair point, if you have modular construction with redundancy you can replace
"factory parts" that break/rust/fail. I wonder what the repair process looks
like for a bridge or other structure that's "printed out of the box" (on
site).

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papercrane
You know what would be really cool? Something like this on the Moon or Mars. I
bet you could get some really wild structures in a low-gravity environment.

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tim333
That's a cool idea. They do it using robot controlled arc welders with welding
wire fed in.

