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.


Storefront debut!

I’ve taken another important (albeit microscopic) step towards complete puzzle industry domination: I have opened an Etsy store. You can find it here. I have some extra square-to-pentagon and square-to-hexagon puzzles so if you want one, they’re a lot easier to obtain now.

One thing that has surprised me is how much people like the way these puzzles look and feel. I keep hearing I should sell them as dining room or living room accessories because they’re the right size to be coasters and because they look very modern and bright. I’m just a puzzle geek so I don’t really know what to make of this feedback. They call them “Puzzle Coasters”.

My friends say I should make more of an effort at selling them so I figure Etsy is a good way to put my toe in the online sales water.

My First Puzzle

Here it is, the puzzle that started my lifelong interest:



Not the Rubik’s Cube – that’s in the picture for scale – it’s the wooden burr puzzle. It’s a simple six-piece burr puzzle, well-made (but hardly an objet d’art), and my grandmother gave it to me when I was in 5the or 6th grade. Over the years, she and others in my family contributed all kinds of different puzzles to my collection. I plan to blog about them periodically as I did yesterday about Rainer Popp’s Tricklock T8.



Popp’s Tricklock T8

I’ve been meaning to post reviews of some of my favorite puzzles for a while now and Rainer Popp‘s Tricklock T8 has the honor of being my first review!

I will be brief:

  1. It is really expensive.
  2. It is beautifully made. I mean it, it’s gorgeous. It is made from stainless steel, brass, and has some details (e.g., a dot of red paint) that make it look fantastic. It is precision made with high tolerances that give it a very pleasing, smooth feel.
  3. The locking mechanism is ingenious and unusual. I know of no other puzzle that uses the same principle.
  4. Like the best puzzles, it is easy and quick to solve if you know the trick.

That’s about it. Here’s a picture of it:

Tricklock T8

(I’ve included the Rubik’s Cube for scale.)

Other folks have reviewed it too:

So as you can see, everyone who plays with this puzzle is pretty impressed with it.

More Square Dissection Puzzles

Well, I sold my first batch of puzzles (the triangle and greek cross puzzles) and have moved on to more difficult ones. Henry Dudeney, brilliant guy that he is, came up with a dissection for turning a square into a pentagon and you can read about his method and the misprint I found in the diagram accompanying his solution here.

I also found a dissection for turning a square into a hexagon by Harry Lindgren. He wrote about it in the November, 1961 issue of Scientific American and I found it through this link which unfortunately misspells Lindgren’s name as “Lindgreen” here and then it gets misspelled again as “Lundgren” here. But anyhow, it’s a really clever dissection and I went and made a bunch.

I also found another square-to-hexagon dissection that’s much older than Lindgren’s. A Belgian mathematician by the name of Paul Busschop came up with one in the late 1800’s and here is a Wolfram demonstration of it. In case you’re interested, there is a wonderful and detailed geometric construction for this dissection here. It attributes this approach to E. Lucas in 1891 but I think that is a mistake because this link to Google Books’ online version of “Dissections: Plane and Fancy” by Greg N. Frederickson gives some background on Busschop and claims, “However Catalan was kind enough to supply Busschop’s full manuscript to Edouard Lucas, who included the dissection in (Lucas 1883).” History is complicated; I’ll stick with math.

So without further ado, here are pictures of the pentagon and hexagon dissection puzzles I made:


(As usual, I put a Rubik’s Cube in the picture for scale.)

More pictures of the puzzles and a little more info (e.g., links to their solution) are on my Items for Sale page.


A Note on Henry Dudeney’s Pentagon-Square Dissection

Henry Dudeney gives a method for dissecting a square so that its pieces can be rearranged to form a pentagon. I found it in a copy of Dudeney’s book “Amusements in Mathematics” on Project Guetnberg here. It is puzzle #155 (“Pentagon and Square”) and I found another copy of it here:

You will notice that two points are labeled ‘F’, one inside the pentagon and one inside the square. I’m embarrassed to say it took me a good fifteen minutes to sort this out but the one inside the square should be labeled ‘E’. I am further embarrassed to say I didn’t know what “mean proportional” meant in his instructions. Uncle Google to the rescue!

Great Puzzle Websites

Hola! This is my first blog entry and I thought I’d start by sharing some incredibly useful websites I’ve come across over the years. In no particular order, here they are:

Some of the puzzles shown on these websites are absolutely brilliant.