Sorry to bump this older thread but its still worth discussing…
I have tried using 1.75mm PLA, Stainless Steel PLA, ABS and PVA. Some of the higher quality regular PLA material works very, very well and I have had some nice prints with it.
The rest of the materials have the same problem - the filament is too small in diameter (or in the case of PVA too flexible) for the feed path into the hotend. The outer clip with the two twist screws that keeps pressure on the filament and the feed gear isn’t snug or doing it’s job really. The diameter of the hole between the feed gear and the hotend is clearly better for a 3mm size and just like others have posted, the 1.75 filament overlaps itself or bunches into an S curve.
My thought on all this would be to make some simple modifications to keep the pressure from warping the filament as its going along…
A small metal or maybe polycarbonate tube that slides into the toolhead below the feeding gear. It could act as a size adapter and keep the smaller 1.75 filament from bunching.
A modified outer clip with the two twist screws to keep better pressure between filament and feeding gear.
Sorry for my lack of terminology, I’m relatively new to all this and I hope you understand what I’m trying to say. Would love any thoughts or experience on all this as I am trying to switch to 1.75mm filament entirely. I am using a Taz 5 with dual extruder v2.