Math is always lurking somewhere

We have been printing like mad these days to prepare objects for the researchers night, and some of them will be used by the scientists at ICTP as a visual help while explaining their fields of study to the schools during that day. One really fascinating object to print is the Menger sponge, but my first experiment did not turn out that well.

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So the obvious solution was to print it with the largest possible base, so with the diagonal surface on the printing bed (difficult to explain, and even more difficutl to do!)

So not this way:

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But this way!

Menger3 half stl

It’s very easy to visualize, but Makerware does not have the nice feature “lay flat” that Cura has, so it’s a matter of finding the right angle of rotation. And it’s much more difficult then I would have thought! I tried first just rotating it until visually it was correct, then I tried analyzing the angles… But I always ended up with this. The surface touched the platform just on one side and obviously the whole print was ruined.

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I admit it: math was not my favorite subject and geometry gave me a headache right from the beginning. After many more unsuccesful tries I asked Carlo for help, and he sent me this link

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Where the angle is then calculated as 54.7°

Sounds completely crazy, but I had to try it so I processed the file yesterday, fed it into the repliacator today and HURRAY, the raft is perfect and it’s building it up nicely.

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the second version printed out much better, no overhangs and all the small holes are perfectly square.

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The only annoying thing is that the raft peels off easily, but the first layer after is never perfect, so the diagonal surface (that is particularly significant in this mathematical model) doesn’t look that great now.

Maybe I’ll keep one of both orientation also to show the differences.

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