I wanted to make a topographic 3D model of some local hiking trails so I did a little research and figured out how to do it using my SO3. The first trial was very satisfying and I can’t wait to scale it up and make a much nicer version.
Step 1. Go to http://jthatch.com/Terrain2STL/ and create a STL file for the area you want model
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Step 2. Download Autodesk Meshmixer (free) which will allow you to slice off any parts of the model that you don’t want to mill. Use the “Edit” then “Plane Cut” to trim the edges that you don’t want. Once you select Plane Cut you just click a spot then drag the line to another spot and it will slice a plane along that line. If you want to slice off the opposite side then just make the line in the opposite direction.
Step 3. Load the STL into your favorite 3D milling software, adjust the z scale to your liking and start cutting away. I used MeshCAM which worked well for this model. I used a 1/8" ball mill moving at 150 IPM to make this model. I went fast and used a sizeable step over because I just wanted to test everything out before I scale it up and make a much larger model with better wood and a nice finish. This one took around 3 hours to mill out of 3/4" plywood. For this I just marked roads in blue and trails in red using an ink pen. For the large scale version I’ll use aircraft grade plywood, sand everything relatively smooth and use a pen striping tape to mark trails and roads, unless I can find something better.
The picture below shows a larger scale part of the model that was milled out of two layers of 3/4" ply glued together. I used a 1/4" ball mill and around 0.2" step over just to cut it out quickly. I think the whole thing took about 45 minutes to cut out.
Next step is to make a much larger scale version using better ply and optimized settings and then let the machine go at it for an entire day.