Printing Plastic Parts for ConstructionPosted: October 9, 2011
On a recent visit to my daughter’s school, I sat and listened to her art teacher who explained their project for the year being an origami based dwelling. The good intention is that you’d be able to easily ship a light weight flat pack of materials to a possible disaster recovery site, and instantly pop up a dwelling. Well, of course there are already hundreds, or thousands of instant tent designs out in the world already, but it is a high school art project, and the origami throws a bit of a twist on the concept.
In talking with my daughter about the parameters of the build, one of the interesting aspects was a raised floor. My thought was, if you’re in a flooded area, why would you build a dwelling in water? You’d first just move to high dry ground, and go from there. But, it’s not up to me to figure out the constraints, I’m sure there is a valid need for a raised floor. This poses a particular challenge. Getting a load bearing floor into easily liftable flat pack form didn’t seem obvious.
Then I walked by a store front display that had some cardboard pieces with notches cut into them. Seeing that display I thought about torsion boxes, and how you could construct them using light weight materials. My thought was to use corrugated plastic panels. These are light weight, fairly strong on their own, and come in bio-sensitive forms (recycled, recyclable). To use it for flooring, there are two things. One is to stand the pieces such that the holes that run through them are directed vertically. This way, they can take the most compression, which is what is needed to support flooring. The second is they need to be secured at the vertices such that they can resist a certain amount of shear and twist forces.
As I was thinking through all sorts of “L” brackets, glues, and whatnot, I thought about just constructing a simple plastic piece that could be used to support the vertices. So, I sat down with OpenScad, and fiddled about for 10 minutes, and came up with the following:
This is a very simple design for Quad Connector to hold things together at a joint in a torsion box. Being OpenScad, you can adjust the amount of the gap, to match the material thickness. Similarly, you can adjust the height and length of the walls, to get more or less support, depending on the nature of the wall material.
I added cutouts to each of the quadrants because I don’t think having the extra plastic is necessary, thus saving on both print time and overall piece cost. I also thought it looked a bit nicer to have the scalloped corners. I could have gone the other way and made it a circle instead. That might also look nice, and eliminate sharp edges, and still reduce the amount of plastic.
As a final touch, I added a hole in the center. The thinking here is that you could thread some attachment wire, or zip ties or something, up through the bottom, for extra attachment possibilities.
And here is an image of how it might look in action:
In addition to being the flooring material, the paneling can serve as the shipping container as well. That is, the sides and bottomm of the shipping container can be made of panels that are 2ftx4ft, sitting on a palette, then those materials can actually serve as the flooring after the torsion box is formed.
Overall, this design would give a relatively light weight, and strong flooring that would likely be able to support the weight of a couple of high school girls. The added bit of plastic might add just enough stability to make it viable.
The moral to the story for me is, once you have rapid prototyping tools available, you can go from a simple idea to an actual field testable product rapidly. Seems obvious. But really being able to do it is actually quite amazing.
One other thought I had was, what if they’re deploying in the field, and they figure out they need some slight modifications to meet the needs they find locally? Well, if they take a fabrication device, and some raw materials with them, it’s a small matter to send them a new design even over their phone through an SMS, and have them print it locally.
That’s the real true power of personal fabrication, and the ready availability of design files. Any place, any time manufacturing.
At any rate, this has been a fun little project. A little thought provoking due to the constraints of the challenge, and a big reward due to the relative ease with which designs can be considered.