Out of round large herringbone extruder gear

I have had a clicking with my TAZ 4 since I got it, and I have updated it to a Hexagon hotend which comes with a new extruder and all.

I finally decided to figure out what the clicking was as I have read of other people mentioning the same issue. Turns out the large herringbone gear is ever so slightly out of round (mind you these both came from Lulzbot). When the machine would retract there was a click sound if the motor was on the smaller side of the gear. I could see the exact problem with the extruder in my hand. On one side of the herringbone the smaller gear was perfect, not tight, not loose, but on the other side of the large gear there was about a 1mm gap in the teeth so when the direction was reversed it would smack into the other side.

When I decided to figure it out I was printing out a vase that had a tone of retraction and that is when I figured out it only did it when the gear was on one side. Basically it seems to be about 1/4th of the gear is where the main issue is.

I am now printing a new gear with a little bit higher resolution than the original. I plan on taking a lot of measurements to assure it’s accurate and then try it to see if the clicking is gone.

How old was the other gear? they do tend to wear unevenly from what I have seen.

It 4 months old (maybe 200 prints) but it did this from day one. Also the one that came with my printer (around 1.5 years ago now) did it from day one. Wear would be more even I would think.

Well, I printed the new one, installed it and no more clicking. I wonder if they print many parts on only a few printers and my parts just happened to come off one that was out of calibration slightly.

I know the printers used in the printer farm that create the parts get a considerable amount of wear and tear, with a few plastic material failures that can affect the parts being printed.

I also had a clicking sound when I installed the new hotend on my kittaz with it’s very first print. It was an out of round large gear. I replaced it with the gear from my older buda hotend to resolve the problem.


When assembling the extruder it takes about 30 seconds to see if the gear is correct. I might suggest to Lulzbot to add this to there QA checklist. The parts I have printed since I replaced the gear also look a bit nicer. I think that small gap of doing nothing (except clicking) may have affected the print when on the side of the failure.