Potential for large scale 3d printer of concrete

So I’m curious if anyone has considered using the layout and concept of the MPCNC as a large read (LARGE) format 3d printer with concrete. I’m thinking on the lines of being able to print something like an outdoor kitchen or shed etc.

I’ve been reading about 3d printed homes and other such amazing feats with concrete 3d printers the past couple days. I feel like this (MPCNC) could be scaled to accomplish this. I’m not sure how much load the center assembly would bear holding a concrete extruder as it flows.

My initial thoughts would be to use the same conduit we use now as it’s cheap and available. Simply add a second row of tubing inverted below the original. Those tubes could then be connected together using the gap space between the existing bearings on the rollers. I feel like this would reduce flex greatly over large spans. The center assembly would need work to accommodate dual rails though but there would be much less stress overall since there is no milling involved.

The Z axis is the biggest issue. I don’t feel like the existing method would work. I was thinking you could borrow the 4 post design of some 3d printers to raise and lower the entire framework and fix the center gantry for x and y movement only. This kind of weight would most likely call for a step up to a much larger motor (Nema 23 to Nema 34).

The extruder ends of things though well I see some use a peristaltic pump design but not sure how that would work, not to mention nozzle selection.

Just wondering if anyone else has considered this or am I simply thinking I can solve all problems with enough time and modifications to the ever fantastic MPCNC :slight_smile:

The 3D printed house in Russia that news articles were talking about yesterday used a central gantry with an arm that pivoted around the center, while the ‘hot end’ moved in and out on the arm. It has the advantage of being fairly compact since it sits inside the project instead of surrounding the project. Needless to say, a MPCNC style would be much larger, since the entire project needs to fit within the printer. You wouldn’t be using conduit for the tubing, you’d have to have something significantly more substantial (16" sewer pipe maybe?)

I completely agree. I don’t think this format would scale well to do a full size building. That video was pretty impresive but the article that actually made me wonder if this system could do small scale (but extremely large fir MPCNC) was this one.

The guy built a concrete 3d printer out of lumber in his back yard. The photos show it looks pretty decent for a v1 build. He has now upgraded to a metal version that is a 10’ cube (up from 8’) It’s about the largest Prusa format I’ve ever seen.

How do they do the vertical rebar?

That’s a good question. From what I can tell on the 4 or 5 different machines and photos I’ve looked through it doesn’t seem to use rebar vertically. Some show adding a mesh or rods in alternating layers while others seem to use an infill pattern like we do with plastics. Looks like most also fill between the inner shell and outer with foam or some other insulating material.

This just begs the question, with a larger 3D printer, could you make an even larger CNC machine?

I don’t think the MPCNC is a really good basis for concrete printing actually.
It will work, for sure, with some adjustments, but the format doesn’t make it very practical for this application.

If I were you, I would try only for experimental purpose, to learn the very basics of concrete printing, but don’t expect too much.

Depending on how you will feed concrete to the nozzle, you may need a very rigid carriage, and modifying the MPCNC for that, is feasible, but I really don’t think it worth the trouble. You’ll also be very limited in terms of size.

If I were you, I would go for an mobile gantry style, not necessarly super expensive, but much stiffer.

Dang it, you guys seriously… the MPCNC wasn’t big enough so I make the LowRider CNC, apparently that isn’t big enough now you want to print houses…never satisfied… can’t please everyone. ect ect.

HEll yes!!! I’m in!!! Where do I sign up, who has some extra cash and a little land? I can 3D print a house for sure, no doubt in my mind!

Okay, stipulations, the first “house” printed has to be my new facilities and then whoever is donating the capitol and the land can have the next one, then we release the plans, then sell kits, by then someone will want a bigger one.

Seriously though, I’m not scared. I have a welder, an arduino, 3d printer, and a couple cnc’s. I feel like I could build anything at this point.

Bigger you say?

Ya I really like this in concept. However, I think if you want to make a real go at it, and you want to use concrete, then I think a boom truck as they currently have, but with the 3D printing smarts to control the hydraulics and sensors to know where it is would be the way to go. With a nozzle of course.

But to be honest, I’m not sure that concrete is the right solution. For the size of the house that they built, you could build a traditional one just as quick at the same size. So other than being neat, I don’t see it being practical, really.

If you could print in both wood and insulation, then I think you’re getting somewhere. One nozzle can print structural wood mix, the other could print the insulation, both occurring for each layer with enough hardening time. Not sure how toxic smelling the end result would be. It might end up smelling like a big old mdf house.

Good luck doing more than one level though without using floor joists at least. You could design it to leave pockets for the joists, to be inserted later, and you could print the roof potentially depending on how much overhang the “filament” could handle.

There is an episode of Grand Designs where the university used a CNC in a shipping container to build interlocking wall assemblies CNCd from plywood, then filled them with insulation. That’s a nice idea.

You could also print the panels (be it foam or whatever) on location in the horizontal position, then allow some time to cure, then hoist into place.

I think a balance of customization and being practical is what you need to shoot for, personally.

My current shop is a shed, and it’s 16x10, and it doesn’t look anything like a castle. There’s definitely room for improvement here.

Maybe you could start with clay, so if it messes up, you can just put it back in the printer.

I like the boom truck idea. It’s like a super large portable delta style printer. The problem with that is I’ve used and been on those. There is no precision to them and they wave and move so much any print I think we could accomplish with them might look more like abstract art than a building.

Does anyone have a concept on how to go about creating a nozzle or extruder for something like this? My first thought would be to print a small planter box or bench and work up to say a BBQ pit or kitchen island. Not to say that a full size building is out of the question but the scale is daunting.

Clay would be a great modeling device. The only pitfall I see is getting it to work with an extruder. The viscosity of clay is so high I have no idea what kind of pump or mechanism would be needed to feed the nozzle. I’m thinking the curing/firing would be an absolute blast. Would give me a reason to use a flamethrower lol.

Heck, I’d build the flamethrower into the hot end… After all, it is called a ‘hot end’! Working with clay you’d want to add just enough heat to dry the layer, but not so much that you affect the insulation or crack the surfaces. Viscosity isn’t much of an issue if you’re willing to print thin enough layers (and for esthetics you want thin layers) you just add enough water to the mix to make it thin enough to easily pass the nozzle. I like the idea of two nozzles to handle structural vs. insulation material. The biggest issue might be infrastructure that needs to be added after the structure is poured, wiring, heating, etc… If you fill the interstitial spaces with insulating foam it’s tougher to push wiring through. Maybe a third ‘nozzle’ that’s actually a robotic arm to handle placing conduit on the fly?

Of course, I still prefer the model where the ‘printer’ is actually a crawling robot that wanders around pooping out the features needed, instead of some gigantic monster that swivels to reach everywhere…

That makes sense with the clay, good call. I think if you printed the shell leaving the top layers undone you could drop in conduit, pipes, wiring etc and then fill with insulation. Once that’s all done you could then print the top layers sealing it up. I wonder how the existing systems handle issues like bridging for things like porches and roofs. My only thought is they build a temporary bed or form to print on and then once cured tear out the supporting bed area.

+1 for the tiny robot that just crawls around. Bonus points if it also picks up the bag of concrete.

I would think the right mud would be good at insulating and be water proof. If it was stiff enough, it could build little tunnels like conduit that you could use for electrical. I doubt you’d be building a McMansion first go, so you’d have time to figure that out. Start by buying some land in the hills, and build a cabin that looks like the batwing, then worry about making something you can air condition.

Here’s another CNC style structure building concept…


Here’s another CNC style structure building concept… http://www.styrotechcnc.co.nz/cnc-services/architectural

That seems much more realistic. For one thing, I can build one with a CNC machine, and I can find other things to do with my CNC machine after that.

Please, if you don’t mind, design a useful shed that is also a castle, that I can make using my CNC machine. I’ll send you a beer if you do.