Introduction: Cielo: Expanded Atmosphere

About: Jeff Ponitz. Artist in Residence at Autodesk Pier 9. Architect and teacher interested in the relationship between material, geometry, and force.

The word cielo translates to sky, ceiling, canopy, or heavens in Spanish and Italian. It is also used to describe clouds and other atmospheric elements. I've always been fascinated by clouds: they have both a visual weight and a sense of buoyancy. They create atmosphere in both the literal and figurative senses, establishing microclimates of light, heat, and moisture while also setting a mood for the areas under and around them. Clouds inspire daydreaming and creativity--who hasn't laid in the grass looking up at the sky, contemplating life and discovering animals in the clouds? I think a major reason for this is the fact that the sky is constantly changing, often imperceptibly, and we see something new every time we look up.

This project was inspired by the space between the many meanings of cielo. My goal was to construct a "cloud" that could create its own atmosphere, and encourage contemplation and daydreaming.

Step 1: Expanded Surfaces

Cielo is constructed primarily of custom expanded aluminum, created by cutting slits in a carefully arranged pattern on a flat sheet, then applying force to form it into a three-dimensional volume. When a flat sheet gets expanded, it creates a volumetric lattice consisting of hundreds of tiny folds, which gives the expanded volume great strength in multiple directions. Best of all, this is a zero waste process in which no material is discarded (in contrast to a perforated sheet, which wastes material and weakens the sheet). In fact, when you consider that you're increasing the perceived surface area of the original sheet by 25-50%, you could argue it's sub zero waste! Structure, volume, and opening are all interdependent.

Step 2: Controlling the Pattern

Many variables are involved in making an expanded surface pattern: the density, length, and configuration of lines all impact how a flat sheet expands into a three-dimensional volume, and whether it expands at all. For example, patterns with acute angles don't expand very well, so a triangular pattern will not yield great results, but a circle would be ideal. It's often not immediately apparent how well a 2D pattern will translate to a 3D volume; the best way to test this is to laser cut different options and see how they behave. I control these patterns using the parametric design software Grasshopper, but you could also use software such as Processing or Dynamo. If you want to do something really simple, you could even use Adobe Illustrator or even cut a pattern by hand. The most important thing to remember is that every other row of dashed lines must be staggered, so the midpoint of every line is centered between the two adjacent lines.

Step 3: Panelization and Tessellation

Cielo is a modular system that achieves maximum variation and customization through a single standardized panel. However, I wanted a feeling of continuity across the piece: I didn't want people to look at it and immediately notice the individual modules, or for it to feel too repetitive, like you would with a rectangular grid of pieces. To achieve this I based my design on an arrangement of pentagonal cells known as cairo tiling. Each aluminum panel consists of four identical pentagons which create a hexagon. The great thing about this arrangement is that it can rotate and stack on top of itself. Cielo consists of two layers--a bottom layer of four panels, and a top layer of seven panels--which connect to each other to create a super strong space frame.

Step 4: Cutting the Panels

After doing some test cuts on the Metabeam 400 watt laser and the OMAX waterjet, it became clear that the laser was the more appropriate tool for this job. Cutting 0.032" aluminum sheets on the waterjet required a plywood spoilboard underneath for every cut, which undermined my goal of a zero-waste process; Cut times were shorter on the laser (2 hours vs. 3 hours). Most importantly, the laser has a much smaller kerf than the waterjet (0.005" vs. 0.042") which allowed me to cut a denser pattern of linework. The main disadvantage of using the laser was the creation of slag on the underside of the sheet.

Cutting metal on the laser requires a good deal of planning and care. The main thing to look out for is thermoflexing: the laser heats the metal enough to warp it, which can result in collisions. If it cuts too many lines too close to each other, a lot of heat builds up. This is especially true when a single job has over 1,000 cut lines, many of which are only 0.07" away from each other! To prevent thermoflexing, I had to "trick" the laser into cutting a line on one side of the sheet, then cutting the next line far away, then cutting the next line far away from that. To do that, I separated each panel into about 20 smaller jobs, so I could choreograph what was being cut when. The color-coded drawing above shows some of this sequencing.

Step 5: Finishing the Panels

I had to finish each panel before expanding it, which seemed a little counter-intuitive, but it's much easier to finish a continuous flat surface than a three-dimensional one with nooks and crannies.

First, I used an air grinder to grind down the slag on the back face of the panel. While the back face of the panels are not visible, slag does show up in the expanded openings.

Next, I hand sanded the front face of the panel, being careful to maintain a uniform direction of sanding, to give it a brushed finish that would diffuse light and hide minor scratches.

Step 6: Folding the Panels

The first step in transforming a flat sheet into a three-dimensional panel is to fold the edges to create flanges. These flanges give the panel rigidity and allow one panel to be joined to another. The hexagonal geometry of my panels prevented me from using the metal brake for this, so I had to make my own brake bars out of lasercut plywood, and clamp the panel face to the table to prevent the face from blowing out. Tabs were integrated into the flanges at the corners, which could be folded and riveted into place to create a strong, continuous flange around each panel.

Step 7: Expanding the Panels

After experimenting with several different methods for expanding aluminum, including using a hydraulic press and a pneumatic bladder, I found that making a set of simple custom hand tools gave me the highest degree of control over the final result. A lasercut plywood jig was used to secure the aluminum panel while I pushed on the aluminum with two levers--one designed to lock into the center of each cell, and another to work the peripheral zones of the cell. Working with these tools, I discovered that expanding requires you to not only "push" the aluminum, but also to apply some torque--it's a similar motion to driving a stick shift car. By combining the tools in different ways, and applying force in different magnitudes and directions, you can get a good amount of variation in expansion. A series of false floors in the jig allowed me to control how far I expanded each cell.

Step 8: Assembly

Panels were bolted together through their flanges. To join the top and bottom layers to each other, I waterjet a custom aluminum connector.

Step 9: Adding Lighting

Neopixel strips (addressable LEDs) were integrated into the piece to create a customizable lighting element that could be controlled using an Arduino microcontroller. The goal of the lighting was to create a slowly, subtly changing quality of light similar to watching light filter through slowly drifting clouds. This was my first LED/Arduino project, so I got a lot of help from an expert--thank you Scott Killdall! The video below shows a detail of how the color and intensity of the light changes over time.

Step 10: Installation

Cielo is strong and lightweight, which made installation easy. My fellow Artist in Residence Scott McIndoe was kind enough to film me moving the piece, until I asked him to make himself useful and help me avoid ramming it into the staircase.

Cielo is hung with four 1/16" wire ropes, connected to a 1/16" thick aluminum clip that was cut on the waterjet. A turnbuckle at each connection allowed me to level and fine-tune the piece after it hung. I set up all the rigging and cabling beforehand, which required a lot of planning, but once I got the piece up there, hanging only took ten minutes.

After installing Cielo and "living with it" for a couple days, I decided to modify the programming for the lighting. Luckily, I left a USB extension cable plugged into the Arduino atop the piece, so I could easily plug in my laptop and test out different lighting schemes. I will continue to experiment with creating different atmospheres with the piece.

Step 11: Acknowledgements

This project took a lot of help!

First and foremost, the project could not have happened without the support of the Autodesk Pier 9 Artist in Residence program.