We didn’t notice [Nikita]’s post about building a concrete 3D printer, a few months ago, but the idea seems sound: build a basic CNC XY axis and then add a mortar pump and hose to deposit concrete. The video, below, shows the machine in operation.
While it looks interesting, there is essentially no real Z-axis, so this would be limited to some sort of relatively thin forms unless you, perhaps, did a few layers and then further lifted the machine. We also assume wet concrete won’t bridge at all. Still, this might be an interesting project, especially if you have a spare CNC XY axis floating around.
If you buy everything, though, you are looking at an estimated cost of around $7,000 USD. We presume there is enough weight in the concrete that a conventional 3D printer probably isn’t going to cut it. We did wonder, though, if there would be any merit to connecting a conventional plastic-extruding nozzle to be able to lay down support for the concrete.
This might be a good jumping-off point for a more sophisticated machine. In particular, [Nikita] points out that a progressive cavity pump with a variable frequency drive is ideal, because it allows you to vary the extrusion rate and provides a steady flow of concrete. Armed with that knowledge, you could probably figure out the rest pretty easily if you’ve ever built a 3D printer or CNC machine.
Not the first concrete printer we’ve seen, of course. The one we saw before was capable of some pretty amazing things.
its grout,not concrete,which has agregate(rocks)
grout has no real monolithic strength
Or is it mortar? Idk the difference just curious
Grout is cement and water, mortar is cement water and sand, concrete is all of the above plus one or more coarse aggregates. The folks here are very wrong to say that grout and mortar are weaker than concrete though, mortar and grout mixes are often much stronger in compression than concrete, the problem is that a crack in grout or mortar means a 100% failure of the structure as there is nothing to restrain the crack and potent it from propagating through the entire piece while a crack in concrete (still potentially bad) is somewhat restrained by the larger aggregates which help it maintain some structural integrity after a crack develops.
^This, sand a cement has NOT concrete. The strength in concrete is due to the aggregate, this is nothing more than a sand and cement mix, commonly known as mortar. The small sand particles offer no structural support and is very weak. You would not want to build anything with it. This is why walls are made from brick, stone or blocks with mortar to join them, not just layers of mortar.
And that’s why brick walls fall over…
Oops no they don’t….
Addition of fibers is an option used in commercial concrete applications and appears to be the method used by the commercial concrete printing companies.
Would it be possible to place the table on springs so when more material is laid down, it goes down in proportion (no Z-axis required)?
This requires a symmetric model, but I guess it’s most model anyway.
I dont believe springs could be used because you’ll have different things printed that would use different percentages of the printing bed so the weight of a layer can differ a depending on what you are printing.
It could be possible only if you were allways printing the same thing, but then maybe a mould would be more efective.
I think an SLS like process where you apply dry powder in layers and dispense a fine mist of water instead of a laser might work well for printing with a portland cement based mix. Portland cement requires wery little water to set.
That would be very much like the Z-Corp 650 powder bed & binder system unused to have back in 2008.
For 1 m3 of mortar you need around 110 litres of water. For just cement water cement ratio is around 0.5.
Where do you get that ratio figure from? You only need enough water to let the object get enough strength to carry its own weight. Then you can remove uncured dry mix and put the object in a humid environment, or soak it, to make it set to full strength. Unless the object is kept in a very dry environment it will eventually absorb enough water from the air to let the cement fully cure.
Combine with a rapid pick&place machine for controlled aggregate placement. You can tesselate your aggregate to minimise mortar volume and deliberately block expected crack propagation paths. If you wanted to be extra fancy, you could embed interlocking aggregate to provide unusual properties (e.g. appreciable tensile strength), embed post-tensioning cable or rod with unusual routing, etc. You’re already in the small-volume-low-speed realm if you’re considering additive manufacture anyway, so the time hit vs. a poured form has already been taken.
why not put some rocks or other material inside?
There are things you can add to cement/concrete that will dramatically speed up the curing process. They wouldn’t work very well for such a small project but if you were doing the walls for a house where it’d take quite a while to do each cycle, it would probably work just fine.
Dunno why nobody is taking this machine and adding CNC capabilities to it. The mechanism changes could be pretty simple. Enable the head to rotate on a vertical axis and the arm length to change. That would make it a polar plotter type.
It answers the “it’s not concrete because it has no aggregate” argument.
Corners would be rounded. Should be able to have some kind of variable side forming parts to make tighter turns in both directions.
https://www.youtube.com/watch?v=Dl9rhG5BPrM
That video was really cool, well, apart from the bomb shelter aspect I guess
“there is essentially no real Z-axis” I can see a real Z-axis, it’s just limited in range in this model, but for a proof of concept it seems more than sufficient.