I'm helping my daughter with her geometry class, and we got to the part about conic sections (circle, ellipse, parabola, hyperbola). For some reason her teacher failed to cover that subject in class, so I decided to make a visual aid to help her visualize the subject at home. It's a cone divided by planar boundaries, that you can disassemble to see what shape each of the cuts is.
It's not hard to model in Fusion 360:
- Make a cone,
- Draw a sketch from the side with four line segments where you want to planes to go,
- Turn those line segments into planes with "plane at angle", and
- Divide the cone into pieces using "split body".
To attach the pieces together after printing, at first I was considering pegs or a dowel, but then I settled on one of my favorite tricks: magnets. I have a whole bunch of 6mm x 2mm rare-earth magnets, so I cut holes for two of them in each face:
The magnets line up with each other. Here's a picture of the cross-section, for visualization:
Those holes are really tight: 5.9mm for a 6mm magnet. That way, after I've banged them in, there's plenty of friction to keep them from falling out again.
I printed the model in a low-key color scheme... alternating white and beige PLA. No supports, default settings.
With the magnets, it's important to be careful to get them oriented properly so they attract each other, rather than repelling. To do the magnets on one side of each face, I used my "Gridfinity Pressure Fit Magnet Jig". Then for the other side, I stuck the magnet to the first side and placed it by holding the sides together.
The hardest part was figuring how to bang the magnets in with a hammer and getting them to actually go in. Or rather, it was hard until I realized that I should do it by placing the magnet over the hole, putting masking tape over the magnet to hold it in place, and then hitting it with the hammer through the masking tape until it's in the hole. If you use masking tape, it's easy. Bang them in until they're flush, like this:
Here are the five separate pieces. They fit together nicely to make the cone.
Files
Want to make some yourself? Here's the Fusion 360 file, and the STLs.
I bought the "6x2 mm referigerator magnets" from Amazon.
Questions or comments? Email me at .
2024 Jun 2