Hex Press-Fit Puzzle

For this project, I wanted to create a more open-ended modular construction kit, where it is up to the user to determine the output, as many are possible. I chose the hexagon, which is my favorite rigid/regular shape. I made a set with 2 base pieces: A, with spoke outward, and B, with notches and a center hole. I also wanted to see how various kerfs fit together, so I cut a sweep of each shape with kerf adjustments from 0.15-0.35.

• Fusion 360 with Laser Cutter Extension
• Adobe Illustrator
• 6.4mm (0.25 inch) thick birch plywood (approximate)
• laser cutter

First, I made a sketch of a hexagon and extruded it to the material thickness. Then, on one of the extruded sides, I made a sketch to design the spoke or the notch.

I used parameters in Fusion 360 to assign dimensions I could use to make the notches and spokes, and keep them consistent. To make it easier on myself, I made the length and width of the notch and spoke equal to the material thickness, 6.42mm. Click on the image if you want to see the whole window...

Then, I used the circular pattern feature to duplicate the notch or spoke on all sides of the hexagon. For a notch, I extruded into the shape, and made a cut. For a spoke, I did the exact same, but extruded out of the shape.

For piece B, I drew a sketch on the top face and made a square with the notch dimensions, then cut it through.

In hindsight, I wish I had been more intentional with the hex side lengths, because I can't use all 6 spokes on the larger hexagons without the smaller ones running into each other, as you can see in the second image of the cut pieces.

I used the DXF for laser cutting Fusion extension, and exported each shape (the top face) and varied the kerf from 0.15-0.35 in steps of 0.05.

(I forgot to take a photo of this step, and I don't have illustrator... oops).

I opened the DXFs in illustrator and arranged them in increasing kerf order (so I would remember which piece is which). Next time I test kerfs, I would add a raster engrave of the kerf so I don't have to worry about being forgetful.

Then I changed the line stroke to red (255,0,0) and weight to 0.05pt, and printed to the laser cutter.

I made sure to do the Z calibration, and since wood tends to warp, I did so in the center(ish) of my piece.

Pictured here are the combinations of kerf adjustments that made the best fit. I think the best fit is somewhere between 0.15 and 0.20, but I didn't do any further tests because I was happy with what I had. Also, the fit varies across the joint type (center hole vs notch vs spoke) and across pieces with the same kerf. I would guess that this may be due to wood warping, which impacts the material cut in the laser cutter.

After I found the best fitting pieces, I cut more of the 0.15,0.2, and 0.25 kerf hexagons, so I had more pieces to create sculptures with.

Here are 3 different sculptures I made with my pieces. There are many more possible outputs, and if I make more, I'll update the photos here!

I really like hexagons because they're the building block of organic chemistry, so next time I do this, I'll make something that is suitable to visualizing chemical structures. It has always been on my bucket list to make fullerene models, but the angles are super hard to achieve, especially in laser cut pieces. I would also need to add pentagons. Maybe with 3D printing....