© 2011 dogichow resized

Crafted by Nature – Part II

In the last post we got until we started doing our final experiments. Here things started to get out of control. The core concept of our project was lent from sea sponges. Their cell structure consists of general purpose cells, but the orientation of these cells change in response to underwater currents. You can think about this phenomenon the same way as Sun flowers turn their heads to maximize the amount of sunshine hitting, similarly Sea sponges change their structure so they absorb the most nutrients from the sea.

We used a similar analogy when designing our system: we envisioned a chair that used a cell structure to translate mechanical stress (someone sitting on a chair) to a sphere packing (that we fabricated).

We used Topostruct coded by Panagiotis Michalatos from the GSD to create a virtual stress pattern. Topostruct allows you to define points of support (where the chair’s legs touch the ground) and loads (where you sit) and calculates the stress patterns that emerge from such a system. The growth pattern looks like this:

And the stress lines that it yields looks like this:

From the stress lines we created a sphere packing that relies on a simple rule: regions where smaller spheres are present will give structure to the system (needed near contact point with the ground), while large sphere packing results in flexible parts (the seat was made this way).

I wrote a script in Python (actually RhinoPhython that executes in Rhino 3D and is free for Mac, lolz). Its operation is super simple: it voxelizes the space uniformly and depending on density of the stress lines in a given voxel it packs variable sized spheres into the voxel. The range of radii of spheres is a function of the density. A voxel may look like this:

We modeled a whole chair like this and we found it interesting, since we actually did not design the chair at all. The person who’s pressure system we used (khmm. let’s call it ass print) designed the chair for him/herself. Which is cool.

Next step was fabrication. How do we make a sphere packing in real life? Baloons! OK, but how are they going to stay in place? Inspiration:

What we needed was something similar, but less fancy and much bigger. So we hacked a huge trashcan to become a gigantic vacuum chamber, like this:

What you see here is a trashcan with a small hole drilled on its side, where we suck the air out with a pump. The top is sealed with some insulating tape and a huge sheet of plexi with a hole on its center. Into that hole we stretch a huge (7 feet large !!) balloon. Thus when we depressurize the chamber the huge balloon magically inflates, but with its “mouth” open so we can stuff our little balloons in :)

From here it’s relatively straight forward: we recreate the sphere packing that we computationally modeled into the huge balloon. After that we start pouring the mixed casting material into this balloon packed system. We used a Smooth-on product called Task-14 which is a semi-rigid plastic. Here’s a time lapse of the hack:

Stop motion sphere packing I. from David Lakatos on Vimeo.

Stop motion sphere packing II. from David Lakatos on Vimeo.

And this is how it looks at the end:

Any questions? Comment, email please. An exhibition will be featuring this work soon more about this later.

Post a Comment

You must be logged in to post a comment.