How precise is your filament really?

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What can we really verify about the 3D printer filament we use? No much, really. Maybe what material it is, but especially things like extrusion precision across the entire spool are not something that you could just easily measure yourself. But I wanted to know - how good have filament manufacturers become when it comes to producing round, consistent filament, and is there really a difference between a "+-50um" filament and a "+-20um" one?
So I built a custom filament diameter measurement rig, based on cheap, custom sensors units I designed and went to town measuring a bunch of filament. Lots to learn!

I'll be releasing the sensor design after one more round of revisions. They are decent as-is, but can be built to be more reliable and repeatable with a few small changes. Stay tuned!

Filaments tested
DAS FILAMENT PLA https://www.dasfilament.de/filament-spulen/
Prusament PETG http://go.toms3d.org/Prusament
Creality CR-PLA http://go.toms3d.org/CrealityPLA
Breathe3DP PA https://www.breathe-3dp.com/nylon.html
Proto-Pasta PLA http://go.toms3d.org/ProtoTom/

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