Nov 13, 2015 | By Alec

Regular readers will have doubtlessly seen the very impressive concrete 3D printers that are causing an uproar in the construction industry. Usually consisting of gigantic robot arms with an extrusion unit at the end of it, these machines 3D print thick layers of concrete quickly and efficiently, putting up the basic structure of a house in no time. While impressive, that same concept is remarkably harder to recreate on a smaller scale because concrete flows quickly and starts drying before you know it. However, two students from San Francisco have just shared designs that prove that concrete can be a viable material on any scale.

The pair in question are Clayton Muhleman and Alan Cation, who were immersed in 3D printing technology in the fall of 2014. Back in January, we reported on an interesting research project at the Creative Architecture Machines studio and taught by Jason Kelly Johnson and Michael Shiloh at the California College of the Arts’ Digital Craft Lab. Involving students who had no previous experience in making, this ended in an interesting 3D printed robot called Swarmscapers, which is capable of building basic shapes in granular materials such as sand, sawdust, salt and rice.

That previous experience evidently wetted their appetites, as Clayton and Alan became convinced of what 3D printing can do for the building industry. ‘We decided that while sawdust was a really great material for testing our technique, we'd really rather be printing concrete. But in order to use our mobile 3D printer with concrete, we first had to understand a few things about how concrete behaves as a powder bed printer material,’ they explain.

Using that newly acquired knowledge, they have since built a very interesting concrete 3D printer on a smaller scale than we are used to. Featuring a building space of 2' x 3' x 1' (about 60 x 90 x 30 cm), it is a perfect machine for building smaller parts for the construction industry, ‘for art and much more. While we focused on printing sculptural/structural/architectural objects, don't let our architecture bias limit your imagination! You could totally print cool pots and outdoor furniture and sand castles with this machine,’ they say.

What’s more, they have written a very detailed tutorial to help us through the building steps of this interesting machine, which you can find on Instructables here. If you’re interested, this is remarkably simple way of getting your hands on a brand new construction tool – though one that produces quite a lot of mess.

Part of what makes this machine so interesting, is their approach to building. Instead of going from scratch, Clayton and Alan have decided to appropriate a shapoko CNC machine, extending its gantry with 4' x 6' aluminum rails. With Arduino Uno boards for control, a pump to deposit binding agent, this is a remarkably simple way of getting a large scale 3D printer. ‘Shapoko also has information on how to setup the wiring for the motor controls, and it comes with one uno board and a stepper motor shield. The peristaltic pump will need its own uno board and motor shield. We also have a file for our 3d printed motor mounts,’ they say of their choice. As this also contains a lot of messy concrete particles, they have also built a print bed with some sheets of plywood – the files for this and the rest of the building specifics can be found in the tutorial, but it’s a clever approach indeed. To control the pump, the students simply use Rhino, Grasshopper and Firefly  - how easy do you want it?

Now of course 3D printing in concrete requires a lot of sand and cement. ‘You can get away with much less of these materials if you print smaller scale things. We used 1,000 lbs of sand and 500 lbs of cement in order to print 3 objects with a 2' x 3' x 1' volume,’ the students say. ‘We used a 30 grit fine aggregate sand and white cement for the majority of our prints with a 2:1 sand to cement ratio. We used this due to the fine aggregate sand, with a thicker aggregate you could use a 3:1 ratio.’ The binding agent is called polypavement, for which they used a lot of 5 gallon buckets. This particular agent sets through an evaporative process, meaning that the concrete will set initially, becoming stronger over time. You then just have to dig the model out of the messy pile of cement and sand.

Whichever way you look at it, 3D printing itself is messy with this type of material. After leveling the print bed of their custom machine – which they called a ‘craft within itself’ – they had quite a bit of success with building a low resolution model. ‘Normally, in powder bed printing, the bed is precisely leveled by a machine after each layer, so the layer height is known. This number is then subtracted from the overall bed height and your current height in the model is found. Since we are working at low resolution and large scale, we don't really need (nor do we actually have) that much control. So instead of matching our bed height to our model, we just match our model to our layer height!,’ they say.

The key to success seems to have plenty of glue in the reservoir, and just let it go. When 3D printing in concrete –even in this scale – the results won’t be fantastic, but it’s so cool nonetheless. ‘Sit back and watch as your machine does all the work for you. I find this is a good time to measure out more material for the next layer, put on new work gloves, make sure your dust mask is in good shape and contemplate the futility of existence,’ they say. And as you can see in the clip below, you end up with a huge pile of material with a 3D print in the middle. After letting it cure for about 12 hours, you can start excavating. It’s a very impressive method that can, with some fine-tuning, definitely have a future in the building industry.




Posted in 3D Printer



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Andreas wrote at 11/13/2015 4:19:34 PM:

Unfortunately there is a bit too much mess and manual work involved in this machine. I'd think with an automatic concrete/sand hopper that applys new powder layers, and maybe even a heated chamber to increase the evaporation process speed this could be a viable solution for small scale concrete building. Too bad that you would probably have to add some steel/iron reinforcment ot actually make chairs or tables or other functional furniture out of concrete.

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