3D Printed Maze Cube

Welcome to the last installment of assignments from Computational Fabrication (CS 291I)! This week we were tasked to create a set of 3D printed components that either fit together or fit onto existing materials using press fit design.

I was looking up 3D puzzles and came across the "3D Magic Maze Cube" puzzle and decided to recreate it. I happened to have a clear plastic display cube in my house already that I wanted to put the maze in. The box, however, is much larger than the actual 3D magic maze cubes you see online. So I decided to make a larger version to fit for the 3.5in x 3.5in box.

• Rhino (used for design)
• 3D printer
• A plastic or glass box
• Sandpaper

First I took the professor's sample code to do a press fit test and adjusted the parameters to what I desired. It was good to get an idea how snug the press fit would latch onto each test block. I decided to do my own press fit test using the geometry I would have to use to fit the cube together.

The cube press fit is very simple: it is just some part extruded and another part that has a pocket of the same size. It fit very nicely without any adjustments, though I did have to push it in a bit. While doing this step I realized it would be hard to make my design using Rhino's default units so I switched to inches. With some trail and error, I found out that STL and OBJ model files do not save the units so when I would import them into the slicer they would be a different size. I had to export the objects as 3MF files in order to keep the units. Cura would then convert the model back to mm. The third image is a 1in x 1in x 1in cube converted back to mm in the slicer.

I created the maze structures in Rhino for each side. This was done with polylines, planarSrf, extrude, and boolean union commands. For the press fit structure I followed this 3D Magic Cube. The top and bottom of the cube fill the entire area while the sides fill one side but not the other and create a connected cube interlocking each other.

For the ball that would go in the inside of the maze I modeled a simple sphere that has a dimeter of .15in (later changed due to issues) and printed it with a different filament.

When I printed my first iteration of the top piece I noticed an issue. Although the box itself was 3.5in x 3.5in x 3.5in, I had not accounted the fact of the plastic on the inside of the box that actually creates the structure. This part was approximately 0.0625in or 1.58mm in thickness.

To fix this, I used Cura to scale specific dimensions down. It took me some tries to figure out what was a good number as shown from the picture. But in the end I scaled the top and bottom pieces down by 3mm of their original size (2454.29% instead of 2540%) on both the x and y axis and the side pieces down by 2.5713mm (2454.29% instead of 2540%) on the x axis only.

Once all the parts were printed I assembled the pieces as described in the previous step.

There were some mistakes I realized I made when trying to put the assembled cube into the box. Most stemmed from the fact that the assembled cube was slightly too big.

1. The order I put the pieces together caused some places where the ball cannot travel (my bad I forgot to check that when designing the side pieces)
2. The lid also took additional space so I could not close the lid once I put the assembled maze inside.
3. I am unable to remove the cube maze from the plastic box because the cube maze is slightly too big causing a very tight fit - oh well

I fixed the first issue by using the pliers and cutting layers off the top edge so that the lid would close. So the cube is uneven on one side but I can't take the cube out anymore so this is the solution. However, this caused another problem.

4. The ball cannot roll around anymore because it is too tall for the side with the shortened walls.

I fixed issue 4 by adjusting the sphere radius to be 6mm. Since this is a small geometry, the layers may get printed a bit off so I used sandpaper to smooth the edges.

Designing for press fit is hard! I should have targeted making the cube slightly smaller than the actual cube dimensions. This way I could still take the cube out and fix all mistakes.

After doing the fixes for the maze, I put everything together and filmed this short video to show you how the maze works.

Rhino files here!