Progress on Model #808

Model #808 continues to make steady (if slow) progress. I had some prototypes machined from aluminum by a fantastic machine shop, Cantabrigian Mechanics. They are gorgeous, if I may say so myself. Take a look:

808 Preview

The prototype at the top of the picture was bead-blasted, then anodized in black. The one at the bottom of the picture was anodized in black and engraved with lettering, which I then infilled with red. Actually, only the top piece in the bottom prototype was anodized black; if you look carefully you can see the un-anodized bottom piece. I wanted to see what the different finishes and combinations looked like.

This is Rev. 12 and it’s been an amazing journey from Rev. 1. Along the way I’ve learned two CAD tools, OpenSCAD and Onshape; prototyped in ABS, PLA, nylon, and aluminum; built an FDM 3D printer; and tried a bizillion different internal mechanism ideas.

I also dove deep into the world of fonts to find what I was looking for: the machine shop typeface that we’re all used to seeing engraved on heavy equipment. It turns out that almost everyone (e.g., NASA, Boeing) used engraving machines from the Gorton and Graham Machine Co. Here’s a picture from one of their brochures. To my immense good fortune, the typeface has been recreated by a fellow named Josh Kraemer and it can be seen on his website here.

So all the pieces have fallen into place. I think this may be the final design and at this point I’m working with Cantabrigian on getting the dimensions exactly right so that the fit and feel are perfect. Getting closer, almost there!

On the Asymptote to Perfection!

I just received my latest prototype back from the 3-D print service I use (i.materialise – whom I recommend highly) and I’m very happy with this latest revision (the sixth I think!)

The puzzle has two major pieces, the top and bottom, and the biggest design challenge I’ve had so far has been to keep the two pieces aligned while the puzzle solver is manipulating the puzzle. If the pieces move out of alignment, it can put the puzzle into an unsolvable state or it can keep the puzzle in a partially solved state when it oughtn’t. In a previous puzzle I used Vlier pins to hold everything in place and they worked beautifully. Unfortunately, they’re much too expensive so I’m experimenting with some other approaches. Here’re what the top looks like:


I’ve never used this material before. It’s nylon (polyamide) mixed with aluminum powder and it’s called “alumide”. I like the metallic color but overall the finish isn’t as nice as with the matte white nylon so I’ll probably go back to that. Here’s a picture of the bottom:


If you squint you can see the model number embossed on the right end: “Model #873”. If you really squint, you can make out “” embossed on the left. The low print resolution makes it hard to read the text but this is just a prototype. The final version will likely be made from machined aluminum and engraved with the text on the back and the logo on the front.

The good news is that the puzzle mechanism works very reliably so I will press ahead with plans to manufacture a couple of dozen and see if anyone enjoys these things as much as I do.

Puzzle Prototyping with 3D Printing

The summer was way too busy but I nonetheless was able to design and prototype my first mechanical puzzle. It even works!

Building a working prototype turned out to be much easier than I expected now that 3D printing has become so affordable and so widespread. All I had to do was create .STL files (I used OpenSCAD) and take them to a local outfit called Einstein’s Workshop whose fantastically helpful staff (thank you Katy and Matt!) printed them for me.

I tried prototyping a puzzle about twenty years ago by taking my design to a machine shop and that cost me a couple of hundred dollars. The 3D printed prototype, on the other hand, was about a twentieth the cost and took a quarter the time, thanks to the amazing march of technology. Also, even though I made a mistake in the first version of my design it only cost me the wasted 3D print, not the cost of a machine shop’s time and materials.

So here is a picture (the pen is there for scale):


As you can see, the surface finish is pretty rough since it was made using FDM (Fused Deposition Modeling). I’m currently waiting to get back a higher tolerance version that was made using SLS (Selective Laser Sintering) and hopefully that will compare favorably with the smooth finish of machined aluminum. My plan is to iterate my design with 3D printed prototypes until the puzzle is working perfectly; then I will decide whether it’s worth the extra cost of having them machined from aluminum or delrin or something.

Most important is that the puzzle mechanism is working dependably and as it was designed to. I’ve shown it to a couple of friends and the feedback has been positive: it’s very hard to solve but not unfairly so. (At some point I want to write an opinion piece about puzzle “fairness” but that’s a post for another day.) For some reason I’ve always liked dovetail joints on puzzles – I guess that’s why I have all three (1, 2, and 3) of Wil Strijbos’ beautiful cube puzzles (great review here) – and so I couldn’t resist the temptation of using them for my first puzzle.

So anyhow, I have reached the prototype milestone and hopefully I will be able to finish the puzzle design and put it into production before the end of the year. Feel free to comment or email me at kay en oh see kay at-sign pea why are eye gee aye en dot see oh em.