Milling Topography in Wood

I prepared 2 files last week with the objectives of practicing milling wood on the ShopBot and practicing milling wax on the SRM machine. First, I knew I wanted to mill a topographic map of Mount Kenya for a friend, so I researched tutorials for translating a digital elevation model (DEM) to an STL file that would be compatible with the CNC machines at our disposal.

I discovered a website called Terrain2STL that allows you to input latitude and longitude coordinates and export an STL model of your chosen terrain. Amazing! Then, I found a tutorial on how to clean the terrain STL in blender and finalize the geometry in Fusion360. I've embedded screenshots of my process below.

Mount Kenya, elevation: 17,057 feet!

Using Google Earth to grab the exact coordinates of Mount Kenya.

Bringing the coordinates into Terrain2STL and adjusting frame.

Editing STL in Blender, changing triangle mesh to quad mesh.

Defining height of the block in Fusion360 and prepping it for export.

Getting the Material Ready

Although I had only practiced using the ShopBot with the OSB, I didn't want to use that material for my design. In addition, the process of milling the topography would inevitably be more complex than the simple example we were given in class. Ibrahim had suggested I use 2 pieces of plywood glued togethger to give the elevation more depth. I attached the pieces I found with wood glue and clamped them to a table in SC102 overnight. On Tuesday, Ibrahim helped me set up the file for the ShopBot. The tutorial I found had suggested I prep the file in Fusion360 for milling, but we used Aspire instead.

Nathan helped me import the STL file and prep it in Aspire. This required shortening the height of the model because we anticipated that the length of the bit would not be able to cut all the way down the 1.5" height of the plywood board I prepared. The photo of the program below shows how much we were able to mill out.

My first run on the ShopBot, practicing full cuts and pocket cuts.

Although we (sort of) calibrated for the drill bit length ahead of time, it turns out that it still wasn't enough wiggle room to follow through on the entire height of the landscape. It turns out that I would have needed to measure the maximum length of the drill bit, measure the plywood board (which was roughly 1.5"), and use the difference to adjust the height of the topography within Fusion360 or Aspire. As the drill bit reached the height of the plywood, I had to stop the mill job or else it would have hit the top of the board along the way. I was only able to achieve Mount Kenya's peak elevation points, so I probably could have picked a design with less extreme elevation too. On Thursday afternoon, Ibrahim is going to help me adjust the design to try and get a full topographic model milled.

Wax and its Discontents

I will preface this section with the fact that I had a bunch of trouble with the SRM machine; Kassia was really gracious and helpful with troubleshooting, but when we finally got my milling job to work, the outcome was pretty mediocre. My initial idea was to mill a wax mold of mushrooms of different sizes. I wanted to use that mold to create a food-safe silicone mold in which I would cast mushrooms out of chocolate, or even better, truffle butter. Initially, I thought I would just do a 2.5D profile of my mushrooms, so I prepped my Fusion360 file to reflect that direction (3 mushrooms flattened within a box). However, I followed Ibrahim's suggestion during lab to include small columns for each mushroom: one would become the channel for the silicone solution, and one channel would be for air to escape the mold as to avoid air bubbles. Then, I made 2 versions of my file with pegs and holes that could theoretically lock together, making a fully 3D mold that would round out the mushroom shape. On to milling!

Casting the Chocolate Mushrooms

Since I used the food-safe silicone, I bought chocolate chips and tempered them at home. Then, I poured the liquid chocolate into both of my molds, evened off the top layer, and put them in the freezer so they would firm up more quickly. The 2.5D molds turned out well! The mushrooms' curves are smooth and it's fun to see them at different scales. I even fused the 2 big halves together with some extra liquid chocolate, which is a quick solve to make the fully 3D mushroom.

Overall, this was a fun and time-intensive experiment. If I had some more time given my schedule, I would have like to reprint my molds to try the full 3D experience.