This project began as a result of my interest in visualizing potential sea-level rise scenarios for San Francisco. Over the last few years, I have been exploring the implication of sea-level rise for the Bay Area shoreline as a part of my thesis at UC Berkeley. However, this study has remained mostly in the form of digital modeling and paper space. I wanted to create a three-dimensional visualization. As an Artist-in-Resident at Pier 9, I am fortunate to have access to a plethora of digital fabrication tools to make this possible. This led me to create a CNC cut topography of San Francisco out of walnut, with which I could display various 3D printed sea-level rise scenarios.
The final piece is called San Francisco Archipelago because with a 213-foot rise in sea levels the city will be transformed into a series of islands surrounding the remaining land connected peninsula. This extreme scenario is in part inspired by the wonderful article and gorgeous maps by the same name from Burrito Justice and Brian Stokle. 213 feet also happens to be the height that the sea will rise if all the grounded ice in Antarctica melted (IPCC Table 9.3). Why such a dreary scenario? Letís not forget that the San Francisco Bay as we know it has only been around 10,000 years. The original inhabitants of the Bay Area experienced a sea-level rise of 300 feet over the course of 4,000 years. We may very well be at the start of another "sea change" in coastal morphology.
Step 1: Create Topography
My first step was to create the topography of San Francisco. I downloaded a series of 7.5 minute DEM files from the USGS site. I brought these files into ESRI ArcScene software to create a TIN. I then exaggerated the topographic surface by four times for effect. Finally, I exported the geometry as a .wrl file.
USGS DEM: http://bard.wr.usgs.gov/getDEMSMap.html
I imported the .wrl file into Rhino modeling software. First order of business was to resize the mesh geometry to my cut material dimensions. I used the drape tool to create a smooth and clean topographic surface with a flat base. The base and topography were sized to be within the dimensional volume of the cut material. (I had trouble originally importing my geometry into Autodesk Inventor to create the file paths. I then went back into ArcScene to create a TIN surface with less detail by down sampling my DEM raster. I believe that a similar effect could be accomplished my reducing the mesh count in Rhino before draping.)
Step 3: Inventor HSM
Inventor opens .3dm Rhino files directly. HSM is the CAM component of Inventor that I used to create my file paths for the CNC. I programed (3) file paths including a ½" Flat End-Mill for a Pocket Cut, a ¼" Ball End-Mill for the first Parallel pass, and a 1/8" Ball End-Mill for the second Parallel pass. This fine milling gave the topography exceptional detail around the peaks and coastline of San Francisco.
Step 4: CNC Test
Before jumping straight into wood, I decided to give my tool paths a test on a foam block. This also gave me a chance to check out the resolution I could expect from the milling bits. I milled the piece on the 5-Axis DMS Enclosed Router at the Pier 9 Workshop. Pure awesomeness!
Step 5: CNC Walnut
I prepared a 2" thick piece of walnut for the CNC by trimming it evenly on all sides to create a 12"x12"x2" rectangle box. I then screwed it down, from the bottom, to a piece of plywood, which I then used as my hold down. For some of the detailed milling, I brought down the speed of the router to 50 percent so not to break the bit.
Step 6: Wood Finish
To finish the milled walnut topography of San Francisco, I chose Tung Oil. I like this product for the finish look and because it is a relatively "green" product. While it is water-resistant, I did end up using a satin finish on top of the Tung Oil for additional protection.
Step 7: Sea-Level Rise
To model the water as different sea-level rise scenarios I tried a number of techniques. I started first by trying to vacuum form a clear acrylic sheet that I could cut out for different sea levels. This didnít go very well. Not only was the resolution poor, but also it just looked a bit janky.
Next, I decided to pour in place clear resin on top of the walnut topography up to the desired level. This was tedious and unfortunately a bit messy. A couple misplaced drips ended up being a big pain to sand and gouge out later. Also, the resin dried at a slightly higher mark as it settled, making my coastline not entirely accurate with my digital mapping.
Finally, I set my mind to creating a 3D printed sea level. This was one of my original plans, but I had problems creating a Boolean of my topography in Rhino (a common problem, as this type of operation is not ideal for the particular software). I tried a number of techniques and ultimately got it to work through with a series of mesh Boolean operations. I used an Objet resin printer with a glossy Vero Clear material for the sea level.
Being able to 3D print the sea level was a triumph for two reasons. Now I can interchange various sea-level rise scenarios. Additionally, the process is more in line with my interest in the combination of different digital fabrication methods to examine the exactitude and craft of each. I was happy to find that the 3D printed piece fit quite well on top of the CNC cut walnut topography. With the slight exception of the coastline, which was printed in much finer detail than was able to be cut with the 1/8" Ball End-Mill on the CNC.
Step 8: Create a Stand
No art project is complete without its own frame, legs, or stand. In this case, I decided to weld a steel stand for the model and detailed map that will accompany it. For the top, I used a 0.1" sheet of steel. To avoid warping the thin metal sheet, I used spot welding between it and the steel tube. I used a ½" thick steel base, which I cut out on an Omax Waterjet. This probably wasnít necessary, but it sure is precise and nice to use. It also cut out the center hole, in which I placed the steel tube; fitting so snug I almost didnít need to weld it.
Finally, a CNC topography of San Francisco with exchangeable sea levels for all your doomsday predictions! Finished photos to come soonÖ