This cube puzzle is inspired by a puzzle that my son loved when beeing in Thailand. Unfortunately, the wooden puzzle's string broke soon and was not really fixable.

I've drawn up the 4 different cubes that make up the puzzle.

There is a start (ST) and an end(EN) pice, there are 9 streight(S) pieces where the connecting pin is opposite the hole and there are 16 angled(A) pieces where the pin is at 90° to the hole.

See the photo of the pieces stringed out or the below sequence to see the correct way of assembling.

ST-S-A-S-A-S-A-S-A-A-A-A-S-A-S-A-A-A-S-A-A-S-A-A-A-S-EN

The goal is to twist the pices so that a 3 x 3 x 3 cube is assembled.

My son can solve the puzzle behind his back in about 40 sec, it takes me considerably longer.

I'm not providing you with the solution.

As proof that it is possible to solve, see my son solving it behind ihis back:

20mm is a good size for the individual cubes, but the bigger 25mm is also nice.

After printing also a version in 15mm with a large 1mm chamfer and a bigger pin, the 15mm version is now the favourite.

Printing:

To make the pin stronger you need to have the pin on the side, otherwise the pin will break off during assembly. Unfortunately this means you need support under the pin. the hole does not “need” support, but if you are using organic support the hole will be rounder as well.

I also include the Fusion 360 file so that you can change the size to your preferences. Just change the parameter Cube_lenght for differently sized cubes. (You can also change the pin & hole dimensions through the parameters if you want much bigger or smaller cubes)

I used PETG, because the pin might brake when PLA is used, but I have not tried it.

You can also mix up the color of the pieces to make it look nicer. The wooden original had dark and light colored wood, but not in a particular order, just random dark and light wood was used for the pieces.