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Pourquoi 2.85 et pas 3 mm ?

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Pour en finir définitivement avec cette question sur le pourquoi du comment du parce-que nos UM préfèrent le filament de 2.85 au filament de 3.00 mm

Quand le filament est extrudé il fait 2.85 mm +- 0.05 mm, ce qui veut dire qu'on peut le mesurer par endroit comme faisant 2.90 mm ou 2.80 mm : c'est ça tolérance.

Quand le filament passe dans le feeder, il est déformé, surtout quand ce dernier utilise beaucoup de force ce qui le rend partiellement ovale et ce, juste avant de rentrer dans une long tube (le "bowden").

Imaginons que notre filament de 2.85 soit écrasé et devienne ovale de disons 0.1 mm en + au plus large.

Si il faisait au passage du feeder 2.80 mm, il fera alors 2.90 mm : nickel, ça passe.

Si il fait bien 2.85, il fera alors 2.95 : ça passe bien.

Si il faisait 2.90 mm au passage du feeder, il fera alors 3 mm : ça passe aussi.

Prenons notre filament de 3.00 mm et faisons lui subir le même traitement :

Si il faisait 2.95 mm au passage du feeder il fera alors 3.05 mm : ça va passer mais on est déjà 0.05 mm plus large que notre filament de 2.85, mesuré à 2.90 et écrasé à 3.00 mm...

Si il fait pile poil 3.00 mm, il fera 3.10 mm : ça va devenir pénible...

Si il faisait 3.05 mm au passage du feeder, il fera 3.15 mm et là, ça va coincer, c'est certain.

Mais ça coince ou ?

Dans le "bowden" qui est de 1/8" avec ça propre tolérance (1/8" = 3.175 mm) principalement (tolérance à 0.005).

Vous me direz que ça doit bien passer un filament ovale de 3.15 mm dans un tube de 3.170 !

Oui, ça passe, dans l'idéal, avec un filament tout droit et un tube tout droit aussi mais malheureusement, l'arc de cercle que fait le tube le déforme également ne laissant pas beaucoup de place pou un jeu fonctionnel de seulement 0.02 mm

Conclusion : sur les UM, il faut prendre du filament de 2.85 mm au risque de voir les problèmes s'accumuler lors des impressions.

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Merci pour le récapitulatif :)

Sinon pour la petite histoire si vous voulez savoir pourquoi 2.85mm:


2.85mm filament

At Ultimaker we work with a diameter of 2.85mm. The alternative on the market is a 1.75mm diameter, and we’re often asked why we chose to work with 2.85mm and if there are any advantages. The reason is pretty simple - allow me to explain. In the early days when 3D printing was starting to surface there was somewhat of a shortage of 3D printing material. Plastic welding filament was commonly available matching most of the requirements of 3D printing. Therefore it was frequently used because, well, it was available. These plastic welding filaments were, as you may have guessed, 3mm in diameter. Through time, 3mm filament evolved into 2.85mm.

Ultimaker is now almost 5 years old, and looking back we were one of the first companies starting this 3D printing revolution. If you combine the above with our decision to work with a Bowden tube set-up (the feeder motor is at the back; pushing the filament forward) it makes sense that we use 2.85mm filament.

A thicker 2.85mm filament provides more control during its travel than a thin diameter. This is emphasized when printing flexible materials. Saying that, the advantage of 1.75mm mainly comes into play when the feeder motor is mounted on the printhead. The length it has to travel is significantly smaller and therefore easier to control. And another advantage of 1.75mm is when you print very small, like under 10mm, the extrusion flow will be easier to control.

Source: https://ultimaker.com/en/blog/18266-ultimaker-schooling-3d-printing

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