I started noticing this last night on my new printer, it’s been set up for less than a week. Particularly when close to the bed and auto-leveling, I get ticking sounds when the Z axis is moving. It doesn’t seem to cause problems, but since I’m new I don’t know what “normal” is. 
It seems to come from the left side, close to the electronics housing. I’m just checking to see if it’s a possible issue developing and what to do to prevent issues if there are any to worry about.
Have a look at the silver flexible shaft that connects the motor shaft to the lead screw. Are the set screws tight? Does it look out of alignment? Try loosening either the top or bottom 2 set screws to release any tension and retighten.
Thanks for the reply, I’ll do that tonight.
Hi, did the fix work for you? I seem to be having the same issue. Thanks
I inspected the couplers and they appear to be good. I don’t seem to have the proper hex driver for the set screw. But they don’t seem to move improperly. In experimenting with the manual controls it seems to make the noise only when stopping movement. That does seem to imply that it could be a slightly loose set screw. I’ll rummage around, I have some small hex drivers somewhere. Anyone know the exact size?
1.5mm
Thanks for the size. I found one and snugged up the set screws. Not much movement with a reasonable torque level. I figured they wouldn’t take much force. One was a bit stripped. 
It did quiet it down some. It wasn’t that loud to begin with. I still hear it a bit, but it could well be that I just notice it now and didn’t before. Any other bits I should check on while I’m tinkering with it? Prints still come out fine, though I did need to use the Z-offset to get a more reasonable first layer, which also helps get the @!#$@ ABS prints off the bed. Imagine that, after all the reading about people trying to get things to stick, I have trouble getting them not to stick so well. 
If they are sticking that well you are too close. Raise the extruder .05mm and try. If the Z axis is only making noise when it stops and not on each rotation of the stepper, then it is probably backlash or a loose lead screw nut. Can you replicate the noise manually by lifting or pushing on the x axis mounts?
Quite so. I increased the Z offset and that helped a lot. Lifting and pushing on the X axis rails doesn’t make the sound. I do get a small tick on the stepper rotation, but it’s small.
I’m also hearing a ticking on the Z-axis while my mini is printing.
If I touch the flex coupling on the stepper motor closest to the power supply enclosure, I can really feel it ticking. The other side ticks also, but it is harder to feel.
Lulzbot tech support’s answer was to ask if it affected the print quality. Not that I can see, but I don’t like to hear strange noises with no explanation.
I think the software is telling the motor to dither for some reason while it is printing. It may be a setting, so I’ll do a few test prints and see what I can learn.
If someone has ideas on what to try, I’m willing to try them.
Thanks.
Double check it for a crack. You may want to pull the motor off and remove the couple for inspection.
I didn’t see any cracks when moving it in small increments w/ Cura and looking at it with a bright light and magnification.
I did see where it does seem to flex quite a bit, closing down one of the slits to about half what it is normally. But that’s why they used a flex coupling, right?
I won’t take it apart yet since I don’t see any cracks.
Also, I had this clicking noise when it should have been holding the Z axis stable, or relatively stable. When it was printing X or Y, the Z axis was barely moving, but clicking. Like it couldn’t decide between two step points. It did this with both 0.10 and 0.20 layer thicknesses.
Thanks Piercet!
It’s not unusual for the Z to move very slightly while X and Y move around on the same layer. It’s compensating for the slight differences in bed level around the bed.
I found I got rid of much of the noise by removing the bed and tightening up all the screws on the Y axis that live under there. Don’t go nuts, or you’ll pull out the heat-set inserts, but just snug them up. That shouldn’t have affected anything that moves on the Z, but it did help some. I also tightened up all the screws on the steppers and the couplings. There are 2 on the couplings, I missed one set the first time, so keep rotating and looking for them. I also did the procedure to sync the 2 Z screws, mine were a little off.
I still hear a little, but it could just be the couplings flexing a little.
The Z axis sync guide I used is here… https://forum.lulzbot.com/t/is-there-a-maintenance-guide/2675/1
The most likely cause of Z axis ticking is that the X axis is not prefectly parallel to the Y table. (The TABLE, not the platen.) First make sure the frame on your printer is perfectly squared. Make sure the Y axis rods are parallel to the base of the machine, then make sure the X axis rods are parallel to the Y axis rods. Measure from each Y rod to the bottom X rod. If the distances are not equal twist one of the Z axis screws until they are. This should square up your X axis and the noise should be gone.
My Z axes are matched. That was my post ttabbal. 
I’ve been emailing tech support on this. We have yet to come to a conclusion.
I can feel my Z axis ticking when the X or Y is traversing across the bed while printing. This is indeed due to the level compensation that is going on as it tries to eliminate the offset between the corner discs.
However, mine is ticking louder than I would expect, but then again, I have the NEMA17 isolator on my Y axis, so it prints VERY quietly.
If someone else with a mini could just feel their Z axis worm gear while it is printing, and tell me if they can feel a ticking or vibration I would really appreciate it. It changes frequency with how fast the X or Y axis is moving. Long X or Y moves really bring out the noise.
I believe they all do it, but I’m just a picky bastage that notices stuff like this.
This isn’t detrimental to the print quality, but something just seems slightly wrong. I think it’s the Cura software causing it, or the motor control/drive circuit. It might be trying to follow a line, but jumping on either side of that line, and constantly correcting.
I would describe it as a 10 to 50 Hz tick or buzz, depending on how fast either horizontal axis is moving.
If everything is square then it is probably the auto leveling routine trying to find level when the value is somewhere between steps of the motor. It may be stuttering trying to find an even step position. I have a TAZ so I’m not familiar with the exact system on the Mini, but if you can adjust the level on the platen, I would try to set it as dead nuts flat accurate as possible. At least tweak it a Ittle to see if you can stop the stutter.