Filament size: 1.75mm or 3mm?

I want to finish up a printer I started a while back (ORD-Bot, Azteeg X3) and got stuck on getting the extruder working.

The big question that I thought I’d ask this community is: should I go 3mm or 1.75mm?

This won’t be a bowden setup, so I know that’s one reason that people use 1.75.

I already have a couple of good working printers, one using 1.75mm (Kossel Pro) and the newest one using 3mm (TAZ 5), so I have a good collection of both sizes filament around.

I had thought the original reason for the migration to 1.75 was that the 3mm filaments were from pre-existing tech and not sized reliably, and 1.75 was the bright new standard future for FFF. But the TAZ is still using 3mm and people seem to be settling on a 2.85mm standard there.

Does anyone have insight into where the industry is going with filament sizes? And maybe why Luzbot stuck with 3mm?

I tend to prefer 3.00mm filliament. It’s stronger and less likely to break, tends to be more demensionally stable relitive to its size, isn’t as likely to suffer heat creep due to additional material that can absorb the heat, and can take higher feed and retraction speeds before sheering.

The downsides to 3.00mm filliament is that there is less of it available, so it can be hard to find during peak season sometimes. 1.75mm extruder parts are also often slightly cheaper because there is a higher volume. 1.75mm filliament will also conform to a more contorted filliament path then 3.0mm will, so if the printer feed path isn’t designed well, 1.75 can actually work better. The fact that the components are slightly cheaper, and it’s harder to identify poorly made 1.75mm filliament is one of the main reasons you see so much of it from the chinese manufacturers on inexpensive printers.

While 3mm is the stock filament size for Lulzbot, they also provide guidance for building a 1.75mm printhead (

I use both 3mm and 1.75mm filament. As piercet noted, there are more choices available in 1.75mm. The other thing to keep in mind is that you might run into issues keeping the hotend temp where you want it if you use a large diameter nozzle but this is not anything that I have proof of. My largest nozzle is 0.80mm and I have only used 3mm filament with that nozzle.

Historically the best scoring printers in reviews have all been 3mm.

One of those things that makes you go hmmmm.