

3D Printing of a Steel Bridge in Amsterdam - JDDunn9
http://heijmans.nl/en/news/heijmans-and-mx3d-collaborate-3d-printing-steel-bridge-amsterdam/

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Panoramix
I fail to see the hype of 3D printing. We have milling machines for ages. As I
understand it, what printing brings to the table is good niche applications
where the shapes would be difficult for traditional machinery. Or when the
printers are so cheap that "everyone" can afford them (not really there yet).
For most applications it seems more a "because we can" than actually solving a
problem people have.

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IshKebab
Well this particular use seems a bit weird. But in general 3D printers are
extremely useful, mainly as time savers. Yes you _can_ machine most shapes
that you'd want, and you'd probably end up with a nicer result. But it's far
more difficult, expensive and time consuming.

1\. You have to manually do all the work, or at least set up tool paths which
is a pain (and good software for this is even rarer than good solid modelling
software).

2\. You can't do as complicated shapes. I'm not talking fractals, I mean can
you mill a plastic latch as easily as I can 3D print one? No way.

3\. It just takes longer. Once I've done my CAD with 3D printing the work is
basically done. With machining it's only just beginning.

4\. If I make a mistake in my model and have to make a change, it is extremely
quick to just do the modifications and reprint it.

5\. If I want more than one of them I just click print again.

You're right that good 3D printers are still quite expensive (FDM ones aren't
really worth it, but there are SLA printers for a few grand now). However good
milling machines cost a similar amount, and CNC milling machines cost more.

The image problem with 3D printers is because all the cool and _actually_
useful uses are one-off and in companies so they don't get talked about as
much trinkets and jewellery. For example I made a mount at work that attaches
a stepper motor to a linear slide. Can't release it to the world though.

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krschultz
Counter points to all of that:

1\. All of the software that creates printing paths is a derivative of the
work done to turn solid models into milling machine tool paths. That software
has existed for well over 30 years, and the proprietary stuff is excellent.

2\. This is the big advantage of 3D printing. Arbitrarily complex shapes don't
increase the cost. That said, you can do some insane things with a 5-11 axis
machining center.

3\. It's impossible to say as a general rule which one takes longer. If you
have a shape that is relatively close to the full volume of the stock, then
mills will be faster than 3D printing. If you are spending a lot of time
cutting down stock to get close to the final shape, then 3D printing might be
faster. Either way I would expect finishing steps.

4\. Either way you are starting from scratch, this goes back to #3. No one
really wants to do rework unless you are building very expensive industrial
parts in low quantities, and at that scale you are unquestionably milling.

5\. CNC mills are exactly the same. Actually most of the ones in a factory
take the raw feedstock in and spit out finished parts, no human intervention
required. 3D printers generally don't do this yet.

I get the impression you haven't worked with advanced CNC machining centers.
I've worked with $50,000 mills (and $500,000 mills). I've also worked with
$50,000 3D printers. The $50,000 mill beats the pants off the $50,000 3D
printer every day of the week.

At the hobbyist level and a budget of $2,000 things are different, but serious
industrial production is definitely better done on CNC milling machines. If
you are comparing manual mills to CNC 3D printers, that is pretty apples to
oranges. That would be like comparing a CNC mill to a guy holding a hot glue
gun.

Source: I've been a mechanical engineer designing manufacturing systems for
medical devices & nuclear submarines.

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frik
I am pretty sure 3D metallic sinter machines will replace many (not all) CNC
mills/turns (incl 5 axis) machines in the industry in a few years. Some car
manufacturers of expensive sport cars already use them to create whole parts
of the cars engine and its exhaust system. It allows them to print them
complex metallic parts including moving gears all in one step without any
assembly or finishing step at all - something that would require multiple
parts and many human work hours using CNC mills/turns.

Source: I have background in these field as well.

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nashashmi
I am surprised at the negativity here. I learned from the little bit of
information I have gathered from the historical development of computing that
computers were initially only designed for circuitry to _automate_ stuff.
Speed was an afterthought. Fast forward to today, reiterations on speed have
broadened the uses of computers beyond simply automation.

Likewise, this kind of work is not really just about the hype on 3D printing
but it's the ability to automate things. Tomorrow, reiterations on 3D printing
will bring speed, accessibility, and democratization of abilities, not to
mention the lowering of cost.

Then after tomorrow, or maybe even today, we will have 3D dismantling. Again
to automate recycling and reuse of resource.

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jlarocco
> Likewise, this kind of work is not really just about the hype on 3D printing
> but it's the ability to automate things. Tomorrow, reiterations on 3D
> printing will bring speed, accessibility, and democratization of abilities,
> not to mention the lowering of cost.

That argument doesn't work. Computers were the quickest growing and improving
technology in history.

I actually like 3D printing, and think it's pretty neat, but it's also pretty
limited right now. I believe it will improve, probably a lot, but it's asking
a lot comparing to computers.

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nekopa
I guess that is if you mean digital computers. We could sat that _computers_
started in 1801 with the Jacquard Loom, meaning we may have to wait about a
180 years to see what 3D printing turns into.

Then again, could we say that the Jacquard Loom was actually the first 3D
(2D?) printer?

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proee
Seems a lot more practical to have a stick of rebar that a multi-axis robot
can cut and spot weld then to create each member from scratch.

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toomuchtodo
Would spot welding rebar piece by piece convey the same tensile strength as
forming each member?

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sitkack
The process this 3d printing technique is using is welding on top of itself,
so the whole thing is filler material. Definitely not up to code.

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3am
Would this actually be a pretty bad application of 3-d printing? I thought the
metals were generally or exclusively done through sintering, and and for some
reason (may be incorrect) it didn't do as well with tensile & deformation
stress. Not to mention porosity. Seems like something a casted product would
be better for.

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DickingAround
Why don't we have evacuated or argon chamber 3d weld printing? Too much
electricity? That feels like a $5k/month project. Does this already exist? Or
should we build it? :)

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542458
Some Direct metal laser sintering processes [1] use an argon flood already! It
isn't necessary for all metals though.

[1]: [https://www.solidconcepts.com/resources/design-
guidelines/dm...](https://www.solidconcepts.com/resources/design-
guidelines/dmls-design-guidelines/)

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m0llusk
This advances the art, but it is not clear that economies of large scale
production can be easily overcome and thus it is likely that the future will
be a mix of mass produced components assembled by various automated processes.

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toomuchtodo
I noticed both on their website, their article, and their video that they're
using two industrial robots for the task. Why could this not be scaled up with
additional robots working in cooperation for larger jobs? You're limited only
to how quickly the material cures so you can begin using it to further
advance, and the complexity of adding additional workers in the space
constrained 3 dimensional workspace.

