Taz 5 stops extruding at exactly the same point

I work with 3d printers on a daily basis as part of my job, and one of them is a Lulzbot Taz 5. When I first started working with it, it was printing beautifully, but now all of the sudden, its print quality has dropped, as I will explain. I am using unpigmented PLA that is in spec, and has worked well in the past. The Taz will print a 50mm test cube fine, but if I try to print a 3DBenchy, or any other print, it will print the first 1/2 inch fine, then abruptly start leaving only bits of filament for a few layers, then it will extrude nothing. I have already recalibrated every axis on the printer, and the extruder axis several times, but nothing will fix the problem, that I’ve found. Also it looks like it is stripping the filament very slightly, but as far as I know the idler tensioners are very close to the correct setting. Please help as this is one of the nicest printers I’ve worked with, and would like it to be back to its original quality. Thanks in advance.

It’s stopping where it transitions to the area that uses many rapid retractions. Assuming nothing has changed on your retraction software settings, it’s probably a loose Idler arm. The distance between the washers on either side of the springs should be around 8mm to start, narrower if it’s getting retraction issuesIf you are already under 8mm, i’d still tighten it further Also check the diameter to make sure you aren’t way under on fillament diameter (2.6 or so). Also check for a broken idler base, a gummed up idler bearing, or a loose small gear setscrew or loose idler arm.

Thanks. I’ll check it out, to see if that fixes it.

This can also be caused by a weak hot end cooling fan. When you are moving a good amount of plastic through the hot end, it remains cool enough to work. When you get to a section that has a lot of retractions, the plastic isn’t flowing at as high a volume and you start to get heat creep related filament swell resulting in a filament strip out.

I have had problems with three of the small squirrel cage fans. They still spin and blow but they don’t move enough air to prevent the heat creep.

Thanks for the help. Much appreciated.

As it turns out, the problem seemed to be the idler tensioners. I had in addition to this forum post, sent a email to Lulzbot Support, and when they sent me back a reply, I went through the instructions. They mentioned that the distance between the tensioner washers needs to be ~5mm. Once I tighten it up to that and did about 3 cold pulls, it seems to be working like a charm. I also reverted the extruder calibration to its original settings which was M92 E850, then a M500 to save the setting,and a M501 to check that it saved. Thanks for all the help.