NOTE: I am pretty sure the following is not going to be supported by lulzbot.
I recently received my new TAZ 5 and have been very pleased with it, but like others I have a buttload of 1.75mm PLA filament from my previous printer. I figured that the new Hexagon hotend on the TAZ 5 was all metal and did not have the PTFE tube what would be the problem with just sending some 1.75 filament through it. I figured that the main issue would be with retraction, but I am happy to say it worked perfectly.
I took my standard PLA profile and just changed the filament diameter from 2.89 to 1.75, then print a calibration cube. When loading the filament I did not adjust the extruder tension at all. It was dead perfect, wall thickness was dead on, dimensions were dead on, no blobbing, no holes.
Since I tried this I have run full print plates with 1.75mm PLA through the TAZ 5 with zero issues. So for all those out there that have some 1.75mm PLA sitting around, don’t be scared to run it through.
I have not tried this with ABS or any other material as I primarily had PLA.