Saturday, November 19, 2011

Roxanne's Videos, addendum

In response to my last post, Roxanne graciously posted a new video honoring the Rox Box puzzle box I made for her last year, and which I discussed in an earlier post.

Just to clear up a little confusion, I engraved the gemstones but I didn't actually build them.  These were lab-grown gemstones, technically real rubies and sapphires but not natural rubies and sapphires.  Gem Select has a nice, balanced explanation of synthetic gem stones here if you're curious.  It's informative and respectful, but they don't trade in synthetic gems so they aren't pushing a product.

The clear plastic 'windows' in the Rox Box were literally 3D printed already-assembled by building the majority of the puzzle using white material, then switching to transparent material for the last few millimeters.  This is how the model looked when it came out of the printer, embedded in a solid block of white material with a few layers of clear material (at right).

After I cleared the material from the inside of the models I could see through the windows, but the parts were still embedded in unused support material from the build process.

Peeling away the material around the exteriors revealed the finsihed Rox Box parts, complete with their transparent windows for the top and bottom.  This is how the puzzle box looked the first time I got to see it!

Thursday, November 17, 2011

Roxanne's puzzle videos

Roxanne Wong is an extraordinary puzzle collector whose YouTube channel is crowded with reviews of puzzles by various ambitious designers throughout the world. A few are puzzles I've previously discussed or worked on.

George Bell's Dice Box
I built these hinged parts to George Bell's specifications, as described in an earlier blog post.

George Bell's Exploding Ball
George allowed me build my own Exploding Ball last year. In this video Roxanne exhibits a colorful version of it.

Air, by George Hart
This puzzle inspired my Rhombic Dodecahedron puzzle.  George Hart's web page shows examples of the pieces assembled and unassembled.

Cuburr is uniquely optimized for the SD300 build process, as described in an earlier post.

Tuesday, November 8, 2011

Helical Burr Experiment

After seeing my Rhombic Dodecahedron Puzzle Bram Cohen casually suggested a puzzle in which one particular piece has to be put in last.  That is to say, a puzzle in which the pieces must be assembled in a particular sequence.

The picture above shows how the idea might be adapted to one of my swirly 'marble' puzzles: the four pieces must be assembled in the sequence illustrated above because each new piece blocks the movements of the previously installed pieces.

Anxious to try it out, I built a set of pieces without checking their dimensions.  But I encountered some delicate, thin walls while I was peeling the models out of the support material.

 VisCAM revealed some astonishingly thin, wispy structures on the thinnest piece.  Some of the walls taper down to less than 0.1mm near some of the edges.  It held together only because the super-thin portions are anchored to the thicker 'backbone' up the center!
It took a lot of slow, cautious work to free this thin part from the leftover plastic but it came out intact!  Dipping the piece in plastic-welding solvent made it strong enough for functional testing, despite a few frayed-looking edges where the walls taper down to nothing.

Reviewing the measurements it became clear that the super-thin walls had occurred as a result of how two spiral-shaped channels gradually converged inside the puzzle.  Luckily the thin piece would be amply protected by the thicker piece when the puzzle is assembled.
As I'd hoped, the pieces can only be assembled in a specific sequence.  But unfortunately they fit together too tightly, so the last piece wouldn't go in.
I tried to improve the fit by sanding the pieces, but the PVC is just too soft for hand sanding so I resorted to a high-speeed abrasive wheel.  This improved the fit and gave the pieces a nice smooth feel.

Perhaps it's a bad habit to keep building models with such thin walls, as they're extremely vulnerable to breakage while cleaning the model.  But even though they could break during manual cleanup, they don't pose any sort of danger to the build process so the main penalty is the tedious labor.  The SD300 can safely attempt any sort of ridiculous geometry, even if the STL file is riddled with defects, and the worst that might happen is the model might be disintegrate or consume excessive labor during post-build cleaning.

Tuesday, November 1, 2011

Making signs with deeply-engraved letters

This amusing Do Not Disturb sign was adapted from a humorous sign in the animated TV series Moral Orel.  A Thingiverse user shared the design in several formats so it could be built using a laser cutter, robo cutter, or 3D printer.

I built it on the SD300 by starting with ivory/white material for most of the build and then substituting red material for the last layer.  That resulted in neat, sharply-defined letters in deep relief.

I liked the joke so I took it a step further, designing a door hanger and sharing it as a derivative design.  I flattened the design a little, but kept some depth because the relief makes the graphics look attractive.