Loud noise when Z-axis move down  

Re: Loud noise when Z-axis move down

Sounds like something is bit loose and starts to resonate when the printer reaches sweet spot. And if there are no issues in printing then these are the causes I came up with and possible ways to fixes for the issues:

1. Check your z-axis assembly. Are all the screws tightened? None is rattling when the printer descends to sweet spot. Fix as needed. Do not over tighten!
2. Is the Z-axis screw slightly warped? The lower end is without support, so suitably warped axis' lower end might touch the printer body when the axis is lowered to suitable position. Even if it is slightly warped, I don't think it is serious if the printer does not show any other symptoms. Possibly ways to fix the issue are:
   1. You could print z-axis support for the lower end. If the printer works with it fine, this might be you best bet.
   2. Lubricate the z-screw or the whole's inner surface. This might help if the screw touches only slightly.
   3. Widen the whole where the screw vanishes so that the screw does not touch the printer's body anymore
   4. Ask replacement part/z-axix assembly from Prusa if the screw is very warped.
3. Z-axis screw or more likely the rails are dry on some spot and this causes tiny irregular movement -> sound
   1. lubricate the rail and screw SLIGHTLY around the suspected area. Exes amount of grease only collects dust and garbage, so only tiny layer is needed.
4. Screw's thread is not uniform, there's a e.g. tighter place somewhere:
   1. If the printer does not have any problems, stepper is not over heating (more current needed in problematic part of the thread), lubrication might help.
   2. Request a replacement part/z-axis assembly from Prusa.

I don't think there's anything seriously wrong if the print quality is good even on the loud z-heights.

Re: Loud noise when Z-axis move down

Lupin, thanks a lot for the detailed response! I will try your suggestions later.

Re: Loud noise when Z-axis move down

Ok, start with assembly check out first, then with lubrication and if al else fails proceed further. All the time try to identify the source of the sound, but it can be difficult. Don't go overboard with your fixes since the printer works fine otherwise.

And please report back with your findings, we all learn from it.

My issue is gone for unknown reason

Ah, I just realized my issue is gone but I don't know why and when. What I did in the past two weeks:

1. Printing. I guess 50 hours.
2. To troubleshooting other issue, I have ever removed extruder from the Z axis and put it back. However, I have ever done this once before this post and it was not helpful last time.
3. I installed this camera mount on the x motor and uninstalled it. It could be installed easily (just clip) but I am not familiar with it and I may push extra force on the x motor.

RE: RE. My issue is gone for unknown reason

it is possible, that due to your usage of the Mini, it has achieved "break in", i.e., parts have worn together so that they now slide/move smoothly. I should have considered this, but for some reason it didn't occur to me.

"Breaking in" was at some point required for new cars too, especially the engines needed to have easy few thousand (10 000?) kilometers of running and after that oil change was done to remove tiny metal particles which would be floating in the engine oil after the parts of the engine had worn together. These days manufacturing techniques have advanced so far that this is not normally required anymore.

Anyway, next time your z-axis makes noise, it means that there is something wrong. Most likely you have forgot to lubricate it. Done regularly it won't bother you unless something really breaks.