Left Z axis threaded rod binding

I started getting failed prints, first with the PLA coming off the bed (glue stick fixed problem (so I thought)), then suddenly bubble affect on my print about 5mm high (abort print). I checked the Z axis stepper motor alignments according to step #23 of the Service bulletin (https://www.lulzbot.com/sites/default/files/TAZ-6_Square_Frame_service_bulletin.pdf), though my printer did not fall within the serial number range of the bulletin, the Taz 6 printer is about 2 weeks old s/n 25288. Sure enough there was a difference between Left and Right Z axis. Brought back in alignment, next print and all prints afterwards kept failing, out right badly from the nozzle dragging over the dried and bubbled up pla to just plain ugly entirely. Re-align and right back to failure. Checked the entire framing as described in the Service Bulletin. Everything is flush and squared as it should be. Same distance from corner to corner in all directions.

Lots of troubleshooting and searching and reading… long story short, what I found while checking the squaring of the frame is that the left threaded rod felt kind of binding as I would turn it to align it to a measurement. The right rod would turn smoothly and freely. I can’t see any type of adjustment for this. Seems as though the rod is slightly bent or something with the mount that rides the threads.

Attached is a picture as a result. You can see by the slant that the motors aren’t turning in synch, or in my case the left side is binding thus not moving up the appropriate amount, the same amount as the right side.

Also, homing the axis, adjusting to both sides are even, then running it all the way up the Z axis (270mm) works without a problem. That test passes. When I print, it fails. I tried both high detail and standard.

Please let me know if there’s an adjustment I can do or if you need to ship me out another part or if I need to ship this back for warranty repair. I have it apart right now for the squaring of the frame, no sense on putting it back until I can get that rod to spin and move freely.


This first picture is an example of how bad it got, and this is at standard height.

The second picture demonstrates how the vertical axis is crawling to the left.

Reach out to the support team, at LulzBot.com/Support. They’ll be able to help you further diagnose why your left lead screw isn’t turning as freely as the right hand lead screw.

I did contact support, we went through some troubleshooting steps. I swapped the left & right motors, seems the lag followed the motor and began leaning towards the right side slightly; however still at around 7mm in height the left side would bind up and start the failure of the print. The X axis would no longer be level with the right side being up slightly higher than the left and I would then have difficulty getting them to move up the Z axis to get the nozzle away from the print. It seemed to be getting even worse and getting in a bigger jam when failing. I did notice when I had the coupler’s disconnected from the motor housing that the left screw was just as free to turn as the right side and with the coupler’s screwed all the way to the top I could then slide the bar that holds the print head up and down freely (meaning without the jack screw). I could feel some resistance on the lower end of the guide rods. Either one of the rods are not perfectly round or one of the bearings are faulty. Anyways, I shipped it back to them so they can see it and experience it too. Hopefully they’ll give it a more thorough analysis.


Ok, the leadscrew is typically held in place by a top plate with a 608zz bearing and a bottom motor mount block with another 608zz bearing in it. Your leadscrew top should be inside that bearing and flush all the way to the top, at identical height on both leadscrews. If it looks like the leadscrew on one side isn’t pushed up into the top bearing all the way, you need to move the lower motor mount up the frame to press the leadscrew up into that bearing on whichever side is able to move. It is possible for those Z motor mount blocks to slip in shipping or be installed incorrectly in the first place. To move them, loosen the bolts holdiong that motor mount and slide it up then retighten the bolts.

Update from Tech Support:
“The left z-axis was binding and was causing issues with the print. To fix this I had to replace the z-nut. The nut that was previously on was cracked and was not adjusting properly. Once the new nut was on and adjusted the z-binding went away. No other issues were found”