First work on 3d printing and scanning

content/05_3d_printing_scanning.md

++++
+title = "3d Printing and Scanning"
+date = "2018-09-10"
+menu = "main"
+weight = 6
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+
+## Printing
+
+This week's primary assignment is relatively unconstrained: design and print something that couldn't be made with subtractive techniques. I decided to explore curved surfaces with severely constrained accessibility. This was also a good excuse to learn [libfive](https://libfive.com/), since functional shape representations enable a more diverse palette of interesting deformations than traditional b-reps.
+
+### Design
+
+I modeled a small stellated dodecahedron, where each of the stellations is twisted along its axis. In the end, the model I printed looks like this.
+
+![](/img/05_everlasting_gobstopper.jpg#c)
+
+Designing it was mostly a matter of working out trigonometric relations to ensure the various pieces
+would correctly mate. There were many times I made errors in my calculations, and built shapes with
+large gaps or unappealing self-intersections. A number of these steps would have been more easily
+and intuitively expressed as constraints between various sketch and body entities. (It could be an
+interesting research direction to try to merge the functional and constraint based CAD worlds.) But
+ultimately modeling such a shape in traditional CAD would have been much more difficult. The
+twisting operation in particular, while a few lines of code in libfive, would be nearly impossible
+to define in a traditional CAD environment if not provided as a primitive operation.
+
+Using libfive also means that my model is inherently parametric. To give it the best shot at being
+printed without errors, I chose to make it quite chunky. It's also interesting with much thinner
+beams.
+
+![](/img/05_thin_gobstopper.jpg#c)
+
+### Fabrication
+
+This design was printed on CBA's Stratasys Eden printer in a translucent plastic.
+
+## Scanning
+
+For the same reasons it couldn't be manufactured subtractively, the above shape is a very poor
+candidate for 3d scanning. Which is exactly why I wanted to try it.
+
+Results were... as expected.
+