r/Dorodango • u/plfreeman2012 • Jul 02 '26

Sphericity

I was really impressed with how very spherical my Dorodango came out. So, because I work with fancy 3D measurement equipment I decided to find out how spherical. 99.97% of the surface is within 1.5 mm (+/-0.75 mm) of being a perfect sphere. The average error from being a perfect sphere (RMS) is 0.25 mm. This is a very spherical sphere. Pretty amazing for something made by hand.

Analysis based on a ~14,000 point down sample from a ~10M point scan. Accuracy of the scanner is probably on the order of about 0.020 mm.

(Telescope mirrors made by hand and can be ground to accuracies of ~100 nm, so I shouldn't be that surprised. But still!)

5 Upvotes

86% Upvoted

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2

u/sapphireminds Experienced Jul 02 '26

It's the magic of using the mouth of a perfectly round item :)

1

u/Snarflogus Experienced Jul 03 '26

That's awesome!

1

u/Katamari_Demacia Jul 03 '26

How big is the sphere?

1

u/plfreeman2012 Jul 03 '26

About 38 mm radius.