Printing a Building

RedEaredSlider writes "Researchers at the Massachusetts Institute of Technology are trying to push 3-D printing technology even further. Their goals: create whole working machines and perhaps even buildings. Thus far, 3D printing has been used to make shapes of plastic or metal that can be assembled later. These folks want to change that. One idea is to use concrete in a novel way: 'Not only would it be possible to create fanciful, organic-looking shapes that would be difficult or impossible using molds, but the technique could also allow the properties of the concrete itself to vary continuously, producing structures that are both lighter and stronger than conventional concrete. To illustrate this, Keating uses the example of a palm tree compared to a typical structural column. In a concrete column, the properties of the material are constant, resulting in a very heavy structure. But a palm tree’s trunk varies: denser at the outside and lighter toward the center. As part of his thesis research, he has already made sections of concrete with the same kind of variations of density.'"

Comments

A four course dinner?

[Tsingi]

You've been able to replicate a four course dinner (from the article) on the USS Enterprise for, like, ever man!

and Dr. Suess, too!

[Thud457]

The shades of Antoni Gaudi and Nader Khalili approve of this research.

Pretty neat...

[fuzzyfuzzyfungus]

I suspect that, if made practical on a larger scale, this 3D printing will make variable-property concrete substantially more common, cheap, and swift to put up; but it deserves mention that the Roman architects who constructed the dome of the Pantheon actually used a similar strategy of progressively lighter aggregate mixes as they went further up the dome, resulting in a substantially lighter and more durable structure... A very cute trick that would be handy to see revived.

Re:Pretty neat...

[Anonymous Coward]

That "cute trick" needs no revival, it's been used in just about every large scale construction project since well, the Pantheon. This is something wholly different though, since it would allow you to actually vary the density of the concrete within a single application, rather than just stacking progressively lighter applications.

Re:Pretty neat...

[Divebus]

As a kid, I saw an episode of the Jetsons which had a shot of building construction. A large, low profile square box was hoisted into the air and a fully formed building emerged from beneath at about four floors per second. The box must have been one of those printers - and I'm sure someone is going to claim prior art.

Would you download a car?

[alex_guy_CA]

Yes. Yes I would.

Re:Would you download a car?

[Dunbal]

But the cartridge with the materials will cost you $150,000. I guess that's the whole point, actually.

Re:Would you download a car?

[Baloroth]

If the RIAA had its way, the design would be another $100,000 on top of that. Just to, you know, "pay back the artist..ha ha."

Re:Would you download a car?

[Dabido]

So ... download it from work! :-)

Re:Would you download a car?

[Geminii]

What would it cost to buy one and a half tons of pelleted steel from a car scrapyard?

lack of real-world experience

[SethJohnson]

If this grad school student were to spend a summer working with concrete, he would learn that it's not a medium suited for 3-D printing.

Civil engineers would reject any concrete structure design proposed with 3-D printing. They despise cold joints, and if a vertical support consisted of dozens of cold joints, that's a no-go from the beginning. That's just one dimension of this flawed concept. Comparing a flexible material like a palm tree to an absolutely rigid material like concrete is pure folly. Concrete structures don't bend under load. They crack and break.

Seth

Re:lack of real-world experience

[Dunbal]

Yup. Concrete can take a beating when you compress it - like in a column. Come and push on that column laterally and watch the whole thing come falling down. It doesn't shear so well. Not an engineer but I've built a few things...

Re:lack of real-world experience

[nschubach]

I'm not sure you'd do the entire building in one print.

Maybe you print out the foundation "skin", drop some re-bar in specific locations (that are also printed in place) then have a truck come in later to pour the filling concrete. You avoid having to setup/tear down/transport forms. You can make the foundation any size or shape (again, without special forms) and even color without having to dye the entire batch of concrete. (From what I hear, concrete guys love dyed concrete.../sarcasm)

Re:lack of real-world experience

[Overzeetop]

Careful...there are things you can do with concrete which - while quite a bit outside the mainstream of construction - have been used. Naturally, I didn't RTFA, but if the printer can supply an internal web of properly place, ductile material and the concrete can be formed in a continuous process which allows the hydration to occur across the layer interface you could conceivably create some interesting results. It's a long, long way from the 400-800yd cost of concrete today (that's formed, placed, reinforced, and finished, not just the $90-120/yd for the mix), but there are things you could do that would be quite interesting architecturally.

Re:lack of real-world experience

[iggymanz]

reinforced concrete shears wonderfully. nothing to say you can't 3rd print with internal equivalent of rebar caging system, which perhaps also is automatically assembled or perhaps also 3rd formed

Re:lack of real-world experience

[iggymanz]

actually, there are flexible composite concretes, some that even self-heal if stressed to cracking. And of course maybe 3D printing around support system could allow reinforced concrete printing. We're talking about research for future tech, what an old civil engineer would complain about might have no relevance at all if new materials and methods used. Advancement of civilization is all about new materials and new methods of using them.

Re:lack of real-world experience

[Thud457]

Obviously this problem would be best served by two cooperating systems.
Feedstock would be cement for the concrete extrusion robot. The other feedstock would would be rebar which would be formed by some sort of bending robot.

Re:lack of real-world experience

[Anonymous Coward]

And it's ethanol powered!

Re:lack of real-world experience

[morgauxo]

The University of Michigan in cooperation with the Michigan Department of Transportation trialed some flexible concrete that they made a bridge out of. I forget if it goes over I94 or if it is part of I94. Either way it's a busy bridge. So far as I know it has held up fine. Granted, this is not flexible as in rubber, it's not like you or I could walk up to the bridge and bend it. It flexes when the bridge expands and contracts with the big temperature changes between seasons. Conventional concrete bridges have a gap with metal interlocking teeth to accomplish this. Eventually the gap gets filled with dirt, the bridge no longer has room to move and it begins to break down.

Re:lack of real-world experience

[Dunbal]

I'm not a metallurgist but I think that print head would have to get pretty nifty to be able to deposit steel one layer at a time but with the same qualities as traditional steel. Making that stuff correctly is tricky business and if done wrong it will just shatter under very small stresses. I'm not saying it can't be done, I just can't imagine how it could be done. Plastic is one thing, but steel is another kettle of fish.

Re:lack of real-world experience

[Thud457]

Actually, there were some videos of pipe bending robots that made the rounds on the web recently that make Mr. Rodriquez look like a look like a incompetent toddler. Downright fluid and graceful.

Re:lack of real-world experience

[newcastlejon]

reinforced concrete shears wonderfully. nothing to say you can't 3rd print with internal equivalent of rebar caging system, which perhaps also is automatically assembled or perhaps also 3rd formed

You couldn't pre-stress the rebar if you printed it. You could stretch it and print around though, I suppose.

Re:lack of real-world experience

[newcastlejon]

Metals are more suitable for selective laser sintering/melting, but I can't fathom how you would combine this with a method where you deposit concrete. I'd expect the concrete to mix with the metal powder and give some sort of unholy porridge-like substance.

Re:lack of real-world experience

[LWATCDR]

Wow you want to make a print head that sprays out a super think layer of steel? They do metal rapid prototyping but they use laser sintering. http://en.wikipedia.org/wiki/Selective_laser_melting Not really the best solution for building indoors.
The funny thing is the example they gave. Well we do that now. They are called hollow columns.
I do love the idea but it is very iffy.

Re:lack of real-world experience

[LWATCDR]

I was thinking that foam or plastic could do the job with a weather proof shell on the outside.

Re:lack of real-world experience

[mrchaotica]

You'd offset the metal print head above the concrete print head vertically so that the metal on a layer would be formed before the concrete on the same layer.

Or you'd just reinforce your concrete with fiber instead.

Re:lack of real-world experience

[evilviper]

Comparing a flexible material like a palm tree to an absolutely rigid material like concrete is pure folly. Concrete structures don't bend under load. They crack and break.

They compare concrete columns to palm trees AND BONES... How flexible are bones, again?

Re:lack of real-world experience

[Plazmid]

That's pretty much the process that's been proposed by the USC contour crafting group proposed for doing rebar. Print a shell layer, drop in some modular rebar sections,then you fill up the shell with concrete so that your rebar connectors sticks out, and then repeat for the next layer. Another way to do reinforcement is to put a metal coil on your top layer and to print over it, so the coil gets embedded in the concrete. They've actually demonstrated this.

So why stop at just printing in colors? The contour crafting group has proposed putting in tiling, plumbing, electrical wiring, heaters, and strain gauges.

See this paper for more:
http://craft.usc.edu/CC/Welcome_files/resources/AIC2004-Paper.pdf

Re:lack of real-world experience

[drinkypoo]

bending-welding-cutting robot. And another robot to come in from under its armpit and weld rebar to rebar. The welding I refer to above is the same as done to train tracks; polish the end of the rebar, butt it up to the next (also polished) piece, and run a bunch of current through them to weld them together.

If you pumped the various constituents of concrete to the head and mixed them there, then sprayed the 'crete over a freshly welded rebar form then you could both reduce waste and eliminate cold joints between varieties of concrete...

Re:lack of real-world experience

[drinkypoo]

Metals are more suitable for selective laser sintering/melting,

But, why would you want to? There is nothing, and I mean nothing, with the properties of forged steel, except forged steel.

Perhaps if we move manufacturing into space we will get superior materials... like foam steel. And that's not actually superior, except where you want to use it. We could replace most easily replaced structural aluminum extrusions and castings with it to great benefit, for example, and possibly cast iron ones as well.

Point is, whether you're talking about MIM or sintered powder metal, it's inferior to forged metal in the extreme. In a connecting rod, for example, a powder metal rod is not only 10% weaker than forged, but it is more than twice as likely to surpass the elastic limit and actually break, with predictably catastrophic results.*

but I can't fathom how you would combine this with a method where you deposit concrete.

That's the easy part. There are only so many ways of making metal powder into solid metal, and the sintering process is similar to the welding process in that a protective material must be used. Gases can be injected, clay can sometimes be used as in the case of low-melt precious metals, and plastic is becoming increasingly common; the process is called metal injection molding and it is used with some success (and great deals of grumbling) even for gun parts, although I admit that I want to replace mine with forged. It is notable in that it is an inexpensive way to make complex stainless parts, since stainless is difficult to weld, work, or machine compared to mild or even high-carbon steel. The metalwork is simply done moments before the concrete is laid. The only advantage I can see (rebar being a highly solved problem and readily available commodity which can be produced from recycled materials) is that you could shape the surface of the reinforcement structure to more securely hold the concrete. I am not sure, however, how much this could improve structural integrity. I suspect that it's not all that much, but I really have no idea.

Even if the benefits are massive, however, we're back to the comparison to foam steel. We can't do it affordably any time soon. The benefits would have to be utterly gigantic and even then we would use the technology only in special cases because otherwise there is generally no need for it; modern technology is "good enough" to do the jobs that it could help with.

* When International created the 7.3 liter direct-injected T444 engine Ford refers to as the 7.3 liter "PowerStroke" engine, they maintained the geometry of the prior indirect-injected A1?? series engines down to the connecting rods, which enabled them to use "old" stock of forged rods from the prior motors. In order to reduce costs on later motors, Ford went to a powder metal (sintered) connecting rod, which is cheaper mostly because the caps can be "cracked" from the rod rather than separately machined to match. Unfortunately, when combined with the reduction in mass the rod received in '93 to accommodate turbocharging (the wrist pin was enlarged) this actually became an issue in highly-tuned, later-model 7.3 powerstrokes, with their inferior connecting rods, to the point that a heavily built motor will have the rods from the older connecting rods installed.

Re:lack of real-world experience

[drinkypoo]

They compare concrete columns to palm trees AND BONES... How flexible are bones, again?

If they're healthy, they're more flexible than you might imagine. But then, a lot of things move more than most people imagine, say auto body. Most cars flop all over the place, and the hood or roof can expand by several millimeters due to solar heating alone if your paint is in a dark color. Luckily, the paint expands as well, though when it gets very old and UV-damaged it loses its ability to do so — kind of like when you get old and your bones get calcified.

Re:lack of real-world experience

[newcastlejon]

I think you missed my point. Wherever I've seen SLM used for metals it involved a large amount of fine powder, parts of which were melted with a laser or some such, hence the name. I was saying that having the powder there for melting would be difficult if not impossible when you have liquid concrete being sprayed into it.

3D printing with metals - that I've seen - isn't like plastics or concrete where you directly deposit the material layer by layer with a nozzle. Instead the feedstock is all around the part you're making and has to be be kept very dry.

I've never been very good at explaining things, so take a look at a diagram. For all the other replies that say SLM metal is inferior to cast or forged steel, I know this but I was replying to the parent who simply wondered if it could be done. I'm trying to say that it would be very difficult to do; not that it would be a good idea if it was possible.

Re:lack of real-world experience

[iggymanz]

news for you, been done for a couple decades. I was manager of engineering group that designed and had fabricated working parts and tooling by various layer deposition techniques.

Re:lack of real-world experience

[iggymanz]

only 10% weaker, hah no problem. In buildings you don't even go to 25% of the elastic limit. In any case, things have dramatically improved since the days of your engine story with 20 year old tech.

Re:lack of real-world experience

[iggymanz]

there is also a technique called post tensioning, metal "tendons" (cables in the rebar cage) are tightened with jacks after the concrete poured.

decals?

[mtrachtenberg]

OK, this is all wonderful stuff, I suppose. But surely I'm not the only person who is taken aback by reading the article only to find such titles as "the Media Lab’s Sony Corporation Career Development Assistant Professor of Media Arts and Sciences."

I still haven't got used to stadiums being named after corporations; it's a bit of a shock to see that assistant professors are now so named. Do they have to wear decals?

Give me a rep-rap over a corporation any day.

Re:Booring.

[sakdoctor]

Closest you're going to get today: http://reprap.org/wiki/Main_Page

Terrafoam

[Okian Warrior]

This is great! Lots and lots of cheap, usable housing for everyone!

Sounds like Terrafoam to me.

Re:Terrafoam

[Lifyre]

Very cool link. I started reading it to find out about Terrafoam and am now on Chapter 7... Thank you for sharing.

Re:Booring.

[DeadDecoy]

The already have. 3d printers can print their own parts, but it requires some manual assembly to make the 2nd printer. I'm sure it's not a very big leap to extend the printer to have an assembly component as well.

Re:Stop with all the fancy shit

[couchslug]

There is a renewable resource for the people who need simple and cheap structures. It's called "wood".

One can grow it to suit (for example the many "tree farms" in the US), and it doesn't require cement kilns and all the other expensive equipment required throughout the concrete production chain.

Printing metal in-place is not going to work.

[default luser]

And the reality is concrete needs rebar to be strong and a support structure to be truly useful. ,a href="http://www.shapeways.com/themes/stainless_steel_3dprinting_gallery">These are the only people who have made printed 3D metal, and it has two caveats:

(1) Strong, but not as strong as forged metals.
(2) Has to be baked in an oven to transition from powder to solid metal.

So, not really interesting until hey solve the whole in-place metal printing problem. Right now all you can make is trinkets.

Re:Printing metal in-place is not going to work.

[Darth Snowshoe]

Progress is going to be made mostly by people who research and try new things, and very seldom by people who say "That'll never work! Myuh myuh myuh!"

Re:Stop with all the fancy shit

[nschubach]

Well, If you could print out concrete sections faster than you can pour and wait for them to cure, with less human labor it may be cheaper to use an exotic construction method like printing.

Re:Stop with all the fancy shit

[digitalsolo]

Do you really think that 3D printing is a better solution to that issue than, say, manual labor?

3D printing is intended for complex structures that are otherwise difficult/impossible . Not cinder brick shanties.

Irrelevant Example

[arisvega]

Tree trunks are indeed denser towards the outer region, but that's because they use the middle region to draw water. Perhaps he needs a more elegant example to sell his idea?

Re:Irrelevant Example

[Anonymous Coward]

The middle region is only used for support. It is less dense BECAUSE it has withdrawn the water.

A better example is bone. The central core is more like a foam structure providing cross bracing for a solid outer layer cylinder.

Contour Crafting

[jeti]

Reminds me of the Contour Crafting I read about a few years ago. What happened to that?

Re:Contour Crafting

[Geminii]

Short answer: Nobody wants an all-concrete house. Professor K is a great mechanical engineer, and the concrete printer did what it said on the tin, but at the end of the day it only printed out concrete.

(Source: I was an international rep for Contour Crafting for a while.)

I still think the idea's great - it just needs to be combined with printers/assemblers for other materials in order to not be relegated to a niche market of printing out driveways, ornamental walls, and statues.

ok i get it

[nimbius]

a dedicated subset of slashdotters think 3d printing is the salvation of all mankind. its not.
3d printing a building completely disregards the fact that buildings are designed to withstand earthquakes, wind, fire, flood, and a host of other
complex forces that even a cursory glance at your whimsical little makerbot will confirm do not in fact just stop existing because you learned
how to extrude hot plastic and layer it into fun little shapes. things like ventilation, plumbing, and electricity are hard enough without some
shitty graduate students wormscrew-driven toy factored into the equation. If you dont believe me, drive downtown and take a look at the sheer amount of
equipment and manpower required to erect a multi-story building. you'll spend two months just digging the foundation before your squeezy cheeze
manufacturing system is found to be completely incompatible with a marsh surface like chicago. Or start constructing only to realize your plastic extruded window
frames dont work with the arizona sun, causing every floor-to-ceiling glass inlay to explode under thermal expansion forces at about noon. or recoil in horror when
you find a crack at the corner of the building which should have stopped at 5" instead extends the length of the building and through the foundation.

Re:ok i get it

[AdamInParadise]

What make you think that all those constraints cannot be taken into account?

Re:ok i get it

[jeti]

If you look at the Contour Crafting project, it basically prints the wall surfaces using a special concrete. They are used like a formwork and later get filled with standard concrete. You could add other materials like steel cables. As a plus, the printed surface has a very nice finish that you can leave just as it is. You can also print holes right into the wall instead of drilling them afterwards.

I don't think the contour crafting project will ever be built at full scale, but the idea is IMO not doomed from the start.

Re:ok i get it

[fikx]

the end point of 3D printing is not all-one-piece items. It is intended to be able to create any structures or structures in one "print run" . Being able to create interesting one-piece structures is just a side effect of the building method that is showing to have some interesting potential.

Re:ok i get it

[hot soldering iron]

You sound like someone afraid of being replaced by a small shell script.

Re:ok i get it

[mrchaotica]

Counterexample: an igloo.

Prof. Neri Oxman

[Sebastopol]

I was thoroughly engaged with my "science and engineering mode" brain active while reading all of this information, that is until Prof. Neri Oxman appeared in the second video and my brain exploded. A quick google images search later and OMFG she's an effing supermodel.

I'm highly disappointed in my scumbag brain for such a base detour from a truly intellectual endeavor.

Re:Prof. Neri Oxman

[Toonol]

Holy Crap, you aren't exaggerating.

Re:Prof. Neri Oxman

[Anonymous Coward]

My "science and engineering mode" brain had all it's blood drained....

Re:Stop with all the fancy shit

[Jeng]

Cheap and simple structures have been developed for thousands of years, the world has cheap and simple structures down pat.

Tents, teepees, igloos, long houses, lean twos, tar paper shacks, wigwams, the list of cheap and simple structure designs goes on and on.

If there is to be any progress in structure designs then we want to go complex and expensive. And perhaps some technology that is developed for complex and expensive structures may just work their way down also to the cheap and simple designs.

Contour Crafting

[kruhft]

http://www.youtube.com/watch?v=-yv-IWdSdns

Re:Booring.

[TheRaven64]

Nonsense. They can print their purely mechanical components. No 3D printers can yet print any of these required components:

• Wires (although a few can print circuit boards)
• Electric motors
• Any electronic components, including (but not limited to) ICs

A word about Neanderthals

[RonTheHurler]

Did you know that Neanderthals had bigger brains than we do?
Do you know why? Because they had a working memory!

"Researchers at the Massachusetts Institute of Technology are trying to push 3-D printing technology even further. Their goals: create whole working machines and perhaps even buildings. Thus far, 3D printing has been used to make shapes of plastic or metal that can be assembled later. "

Right. How about this:
  http://www.physorg.com/news190873132.html -- printing structures on the moon.
  http://www.blueprintmagazine.co.uk/index.php/architecture/the-worlds-first-printed-building/
  http://hardware.slashdot.org/story/11/09/16/173210/Printing-a-Building?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Slashdot%2Fslashdot+(Slashdot)

Functional Machines:
  http://www.psfk.com/2011/03/3d-printing-a-lightweight-super-strong-bicycle.html
  http://www.liveleak.com/view?i=01e_1310566165

The list goes on...

(And -- RIght-on Nimbius!)
 

upload the new patch?

[bwnunnally]

Also a self-monitoring and repairing capability for the building would be nice. Although I suppose it would be alarming if you got a message to reboot the building after NEW Building 3.0 was downloaded.

Re:Booring.

[simcop2387]

Motors I'm not sure about (not sure how the coils get wound, never looked into it). But the ICs are automated in manufacturing, so you could probably add that into the whole setup. It would be difficult but I'd say we're really really close to building a factory factory that produces factory factories.

Not true!

[dristoph]

"Thus far, 3D printing has been used to make shapes of plastic or metal that can be assembled later."

This is incorrect. There is at least some 3D printing technology today which makes it possible to print at least basic mechanical parts with no assembly required. Here is a video demonstrating its use, printing a working crescent wrench (including the worm drive for adjusting the size of the grip):
http://www.youtube.com/watch?v=ZboxMsSz5Aw

Amazing, no? That said, the idea of printing out variable-density concrete and applying the technology to large-scale structures is pretty amazing too.

Not new, in the end

[Ralph Spoilsport]

Thomas Edison built concrete houses in the early 20th century.

http://www.disinfo.com/2010/12/thomas-edisons-concrete-houses/

Awful places. Damp. Cold in the winter. Just awful. Just because it was "printed" with concrete won't make it better. It'll still be a concrete house. Damp. Cold in the winter. Just awful.

Re:Not new, in the end

[LWATCDR]

Okay I live in FL and most homes are concrete here. A lot of block but a growing number are cast.
You do not leave bare concrete and you do insulate them. My many of my schools where also CBS and they where not damp or cold.

Re:Not new, in the end

[drinkypoo]

You frame the inside with cheap, light lumber, with studs placed 2' apart, and then slap some insulation and sheet rock up. Done and done. Now it's actually more comfortable than a timber frame with chip board outer walls and sawdust siding.

Re:Booring.

[TheRaven64]

ICs require a lot of machinery to produce. The cost of a wafer fab is measured in billions of dollars. Even if you start with clean silicon wafers as the input, you've got a lot of work to etch the die and then package it. Every IC requires a lot of complicated setup for that specific chip. We don't have factories that you can just upload a mask to and get a single IC out, we have factories where you set up a mask and then do a production run of a few tens of thousands of chips (at least) because otherwise it isn't worth the cost of the setup.

What 's wrong with the old method..

[formfeed]

..of enslaving the local population and having them cut granite to build monuments in your name?

3D on the nano

[Commontwist]

The heck with concrete. I'll consider 3D printing tech truly accomplished when they can actually print using layers of silicon and carbon atoms, forming up molecular bonds in lattices and matrices as the structure is built. True, flawless stone reinforced by carbon nanotube meshes sealed by diamond!

Would that be more or less stronger than concrete and by how much?

One Itsy Bitsy Problem

[FlyingGuy]

While I think 3d printing has some real value and use I don't think this will work out unless there is a major breakthrough in the chemistry of it all.

The fastest curing concrete I know of that has any real strength is the stuff that CalTrans uses to fix big cracks in concrete roadbeds and it takes an hour.

Now the cool thing about the 3rd "printing" of most solids is that the material is in powder form and and a laser is used to fuse small amounts at a time and then build on that until you have the desired shape. Because you are subject only to the limitations of the lasers focusing ability and the supporting ability of the surrounding powdered material you can do very complex shapes.

Since the fasting curing concrete takes about an hour I can t see how trying to apply this technique is feasible. Concrete can only stacked so tall when it it in its uncured state before it slumps. Not only that but the actual cement has little if any structural strength. It is not until the cement is mixed with a material such as sand and gravel of various sizes that it gains strength from the material that it holds in a matrix and thus supporting itself.

Now concrete is great in compression loads but not so very damn good in shear loads, hence re-bar, pre-stressing etc.. So how could one possibly "print" down layers of cement. Also uncured cement does not bond very well to cured cement as anyone who has ever patched their cement driveway can tell you. I mean even if you had some way of way of making n number of water molecules transit through a matrix dry cement and aggregate to cause the curing reaction at a specified depth, how long would it take that to cure? I know various chemicals have been added to accelerate the process but this typically yields weaker concrete.

Pondering....

Re:One Itsy Bitsy Problem

[Geminii]

Concrete used to solidify faster, a century or so back. The industry actually changed standard formulations to get a slower-setting concrete because it was solidifying before the workers could get it into place.

Sounds like it might be time to dig up and dust off the old methods.

Re:One Itsy Bitsy Problem

[ResidentSourcerer]

It depends on the pace and the pixel size. Obviously, the 'pixel' of concrete has to be larger than the largest aggregate. So you plop down 2" blobs of stiff concrete.

Slump of concrete varies with the stiffness of the mix. The machines that continuously cast curbs seem to be able to leave behind an 8" tall layer of concrete that is solid enough to cure.

So visualize a 'printer' that casts whatever wide by 6" tall layer at a time. Horizontal rebar is placed on top of a layer, and embedded on the next pass. Vertical rebar is held while the machine makes it's pass. Probably short lengths overlapping.

Such a printer would be more like 'turtle graphics' than like raster images.

It would work at a speed that allowed the previous layer to have started to set, but not cure, so that the next layer would bond to it, much like the continuous cast of a large dam is done.

At this point I don't see how to get clean breaks (door, window openings)

But visualize a simple machine that builds a concrete silo by going round and round, adding 6" every two hours.

Damn printer driver

[mbstone]

I bought some land in Albuquerque, and then I downloaded a torrent of a 3BR model home, but I can't get it to print in Adobe.

3D Printing

[raymorphic]

Hmm..Seems *neat* and promising.