I've been getting into twisty puzzles recently. Mainly Rubik's cubes, as well as cubes and puzzles by other companies and designers like WitEden, Mefferts, TomZ, and so on. While looking around, I noticed a few designers are printing one-offs via Shapeways, and other designers are offering their puzzles through Thingiverse. I've been wanting to make a 1x2x3 puzzle for a while, probably making one my own from spare parts, but I happened to see a couple of 1x2x3 designs available on Thingiverse...
Very shortly after Brian, Alex, and Bill got Interlock's 3D printer going, I nudged my way in, and got them to print out a twisty puzzle for me. The puzzle I had printed was this screwless 1x2x3 model.
I decided to go for this one becuase I wanted to have it printed out and ready to go as qucickly as possible. In retrospect, I should have gone for TomZ's 1x2x3 design, for reasons I'll get to later. Anyway... on to the printing!
The printer did a great job of producing the pieces, although it would seem that perhaps the filament was being fed into the printer too quickly, as tolerances were overshot, and much sanding needed to be performed just to get it to fit together...
This design included a "barbell" shaped piece that snapped between the two halves of the core, eliminating the need for screws and springs to hold it together and give it tension. Because of the lack of support material, the printer had a difficult time properly printing out this barbell, as you can see in the following picture. There was nothing to hold it in place, so it got dragged around a bit as the print head moved around.
The next step I took was to sand down the parts to get them to fit. The first thing I tried was sanding the 'feet' that protrude from the wing pieces. I was getting decent results, but then realized that a better solution was to sand the semicircular holes in the cores a bit more, opening them up, making the feet spin in the core more easily.
Between various nights of heading to Interlock to work on this, and without the needed barbell piece, I held it together with a rubber band.
Next, Joe came to my rescue. He extracted the barbell piece out of the STL file, sliced it in half, then printed those two halves for me. This time using the stylish metallic gray filament, rather than the stylish orange filament.
A little bit of super glue, and a little bit of sanding, and they were ready to install inside of the twisty puzzle's core. Within minutes, it was assembled properly for the first time! The barbell/snap assembly is a bit loose, and I think that some of the feet were sanded down a little too much, as there is a lot of play in the fit of the parts.
I was planning on perhaps dyeing it, or just sanding more and stickering it with the expected color scheme (red, orange, green, blue, white, yellow) but Nick had asked me a little about rotational symmetry of the puzzle, and a few minutes later, he had stickered it with blue painter's tape. It was an ingenious solution, as no two pieces are stickered with the same pattern. (Note that you can also see the floppy tolerances on the top left piece of the next photo.)
After playing with it for a while, the barbell is definitely the weak point of the whole thing. I had sanded it a little to get it to turn more smoothly, but now it's way too loose. The wing pieces are a bit floppy due to sanding. I think that these two things can easily be changed for the next print, by first using TomZ's design which can use a screw to hold it together, and also being more cautious while sanding to keep everything within decent tolerances.