3mm, 1.75mm? A few questions.

[Flateric]

Could someone clear up for me the main differences and advantages and disadvantages between 3mm and 1.75mm.

Specifically why did our machines comes with 1.75mm over 3mm.

I have been doing alot of research into all metal hotends and the bulk of the all metal hotends seem to all be 3mm.

I have no personal preference to 1.75mm or 3mm(never used yet). But I do note that the majority of my jams or issues seem to be stemming from the thin 1.75mm filament kinking just before entering the bowden tube.

Most of my personal stockpile of filament thus far has been 1.75mm. But I'm wondering if this is a mistake and perhaps I should start shifting over to 3mm. I would have a wide selection of metal hotends. It seems to me that kinks and binds before the bowden tube would not be as common.

But I truely don't know a thing about 3mm and the unforseen problems I would encounter with it.

A little help and advice from someone who's learned these hard lessons with both please.

Thanks.

[Flateric]

Seriously no one has any advice on this for me?

[cambo3d]

i guess we'll have to try it and see how it works out.

[JohnStack]

i guess we'll have to try it and see how it works out.

Crazy hard to read colors over grey. Thought it was me for a second.

[Polygonhell]

For a very long time in the Reprap community only 3mm was available, mostly because I believe it's the same size used for plastic welding rod.
Over the last few of years 1.75mm has gained popularity.
1.75 gives you better control of the filament at low extrusion pressures (low layer height and low speed), and it requires ~1/3 the pressure to push through a hotend. Note that the gearing on a standard Wades extruder is between 3 and 4 to 1 so you can get the same extrusion rate out of a direct drive extruder on 1.75 as a typical geared extruder on 3mm.
In europe it's not uncommon for vendors to sell filament by the meter resulting in 1.75mm being almost 2x the price of 3mm by weight, in the US, there is almost no difference in price.
With a bowden system it's more complicated, retraction speed is important and 3mm might have an advantage there, the tube for 3mm filament might flex less (hard to say), you certainly have to retract less. Someone on the Delta Robot google groups did some tests and came to the conclusion that 1.75mm was better for a bowden tube, but my guess is it's probably a wash. I've seen good prints out of both 3 and 1.75mm bowden setups.

FWIW the profesional FDM machines use a much smaller stock even less that 1.75. Most of those use DC motors with optical sensors to direct drive filament.

Short version, it's a somewhat arbitrary choice, a lot of newer designs are going with 1.75, it lets you use a direct drive extruder (though SeeMeCNC really don't take advantage of that).