Design and Make a 3D Puzzle Cube (with Fusion360)

I own a 3D printer for a while now but I haven't been using it too much lately, so I wanted to make a simple but fun project to put my Fusion360 knowledge and printer to use.

This 3D Puzzle Cube is a simple but challenging puzzle where you have a bunch of little cubes that you have to position them in a way they build a larger 9x9 cube. The catch is that every cube is tied to each other with an elastic string cord so that there's only one way to put it together.

In this instructable, I'll show how to design your own puzzle in Fusion360, how to print it, and how to assemble it.

I don't know how much experience in Fusion360 you reading this instructable have, so I'll be writing the step by step this way:

General instruction in using a command in Fusion360
- Specific step by step, or sometimes I'll show the step by step in comments on the images

I hope this way it works out for you and learn more about Fusion360

If you want to skip the designing process and start making, jump to step 5.

Supplies

- A 3D Printer

- A computer with Fusion360

You don't really need to own a 3d printer to build this project, you can design the puzzle in Fusion360 and then make each little cube with anything cube-shaped, but you might need a drill and a way to mark the center of the cube... B.

Step 1: Modeling the Cubes

In this step, we'll be modeling the basic cubes for the puzzle.

Open Fusion360 and start by creating a new component. Name it "Cubes".
Then, click the box command (it is in the create dropdown menu) and create a 20mm cube. To do this, after you selected the box command:
- Click the bottom plane.
- Click the origin point.
- Move the mouse around to make a 20x20mm and click
- The box will appear on the screen and then set the height to 20mm.
- Click OK
Using the rectangular pattern, repeat the cube 3 times in each direction to make a 3x3 grid:
- Follow the directions in picture #2
Repeat the rectangular pattern and add 2 more layers of 3x3 cube grid
- To do this, follow the directions in picture #3

You should end with something like a Rubik's cube

Step 2: Make the Template for the Solution

In this step, we will let you create the template for the solution of the puzzle.

Start by activating the top assembly and then create a new component, name it as "string". This will make the cubes look transparent.
- More details on the first image.
Next, create 3 offset planes from the front plane so that they are just in the middle of each layer. The offset value should be 10mm, 30mm, and 50mm
- More details in picture #2
Start a Sketch on the first plane. It will be easier to select the plane if you go to the left side "browser tree" to find it
- More details in picture #3
Make a point in the center of each square (Picture #4) and finish the sketch.
- To make a point, you can find it on the Create dropdown menu.
Repeat the same sketch on each one of the offset planes we created. You should end with something like picture #5
Create a new sketch on the front plane and check the box of "3D Sketch" on the Sketch palette on the right. This will allow you to make a line connecting points from the 3 planes we made.
Create your own solution by connecting different points with the line command.
- You should only pass through each point once
- To make it easier to select each point, you can change the cube component to be unselectable by right-clicking it and selecting "Selectable/Unselectable". Remember to reactivate it when you finish this step
- It can be confusing to "see" where you are going. Rotate the viewing cube to make sure you are doing fine.
- You can see the result in picture #6. Yours can be different than mine but it's ok.
Finish the sketch and select the Pipe command from the Create dropdown menu, select the line we just created and make a pipe of 5mm diameter (picture #7).
With the Fillet command, select the outer edge of each corner and make a fillet of 2.5mm (as seen in picture #8)
- Don't miss any corner! The fillet will make it easier to thread the string later
Select the end face of the pipe and create a new sketch. Deselect the 3D Sketch option and make a circle of 10mm diameter centered with the pipe (picture #9). Finish the sketch and with the Extrude command, make a cylinder of 10mm long as shown on picture #10.
Repeat on the other end.
Make the Cubes component Selectable again by right-clicking on it and click on "Selectable/Unselectable"

This step was kind of long to explain. I hope the instructions and the pictures made it clear. Any doubt or question let me know!

With the steps we've followed so far, you have designed the solution of the puzzle. If you want to go to skip the 3d model export and jump directly to 3d printing, go to the Step 5 where I left the STL file for you to download and the instructions to assembly following your design.

Step 3: "Cut" the Cubes Wit

This step will consist of making a hole on each cube where the pipe we created intersected.

But... If you analyze the whole pipe going through the cubes, you can see that there are only 3 types of cubes: "straight line" cubes, corner cubes, and end cube (picture #1). So this step we will only need to apply it to one of each type and not to the 27 cubes!

To do this:

Activate the Combine command, as the "target body" select one "end cube" and as the "tool body" select the pipe. It may be difficult to select it inside all those cubes, so search the pipe in the browse tree on the left
- Make sure the operation selected is "Cut"
- Check the box in the "Keep tools" option
- Click OK
Repeat the Combine command with the other two types of cubes

Step 4: Export the 3d Models

Using the Make took in Fusion 360 export the different cube models as an STL.

Since there are only 3 types of cubes (end, straight and corner pieces), you only need to export 3 files!

To do this:

Find one of the cubes that you "cut" on the previous step from the Browse tree on the left, right-click on it and select "Save as STL".
A window will open. Click OK to save the STL file.
- Fusion360 gives you the option to send the STL directly to the Slicer of your choice instead of saving it. To do this you can check the "Send to 3D Print Utility" and browse for the program you use.
Repeat for the other two remaining pieces.

In the next step, you will find the STL files I created. If you don't want to know the solution of the puzzle, you can follow the directions I will leave on the following steps to make my version of the puzzle.

Step 5: Prepare to 3d Print

Use the slicer of your choice to prepare the printing of the necessary pieces.

The number of pieces of each kind you will need depends on the solution you designed, so make sure to count each one from the 3d model on Fusion360.

For my design you need to print:

2 End pieces
9 Straight pieces
16 Corner pieces

You can print the straight pieces with no infill if they are placed with the holes oriented vertically (as seen in the 1st picture).

For the other pieces, I used a 2% "Line" infill to reduce the infill needed to the minimum avoiding weird overhangs inside the print. Take a look at the 2nd picture to see what I'm talking about and how the infill should be.

Step 6: Assembly

Start threading the elastic string through one of the end pieces and tie a knot on the bigger side of the hole. The knot should be big enough that it doesn't slip to the other side if the string is pulled.
Keep threading the remaining pieces following the 3d model on fusion360. If you want to assemble my design, follow this order of pieces
- E - S - 3C - S - 2C - S - 3C - S - C - S - 4C - S - C - S - C - S - C - S - E
- E: end piece, S: straight Piece, C: corner piece, 2C means two consecutive corner piece
After you place the last piece, pull the string so that every piece is tight, but not too much, and make a knot in the end. To get an idea of how tight it should be, if the whole thing is left in a table it should maintain its shape, but if it is pulled from both ends, it should be able to stretch.
Cut the excess string.