This video is from a Prusa MK3. It used to be intermittent. But now, whenever the y-axis moves, it makes this zip-tie noise.
I think the source is this bearing, but the high-pitched sound makes it difficult for me to localize.
Does it sound like a dead bearing to you?
The adventure continues.
While removing the idler assembly, I noticed two things. The first is that the noise when away once it was loose. I found that... odd since the linear bearings would not have had a change in load. Then I found the lock nut for one of the screws was also loose. At first, it was nearly impossible to turn. Then It spun freely inside of the plastic housing. (The nut was supposed to be retained by the plastic.)
So, yeah, that screw took some damage over time. (And probably some from my expert disassembly skills.)
The second finding was that after finally removing the idler assembly, I noticed there was a dot on it!
Left is my precision removal technique. Right is the new spare part I printed (years ago). It shows the dot.
I thought it was curious because I did not remember that dot when I assembled the printer.
While re-reading the assembly instructions, I saw this tiny-yet-important-gem:
Take the Y-belt-idler and place it on the front plate. Note there is a mark (circle) on the printed part facing up.
I put the key sentence in bold.
Yeah, so 3(?) years ago, I installed the idler wrong (upside-down). And the "intermittent" noise was likely stress on THAT bearing. So now I do believe the noise is a failing bearing, just not the one I initially thought.
After 1500+ hours of print time, like that, I think it is safe to say I need to replace that pulley's bearing.
The adventure continues.
While removing the idler assembly, I noticed two things. The first is that the noise when away once it was loose. I found that... odd since the linear bearings would not have had a change in load. Then I found the lock nut for one of the screws was also loose. At first, it was nearly impossible to turn. Then It spun freely inside of the plastic housing. (The nut was supposed to be retained by the plastic.)
So, yeah, that screw took some damage over time. (And probably some from my expert disassembly skills.)
The second finding was that after finally removing the idler assembly, I noticed there was a dot on it!
Left is my precision removal technique. Right is the new spare part I printed (years ago). It shows the dot.
I thought it was curious because I did not remember that dot when I assembled the printer.
While re-reading the assembly instructions, I saw this tiny-yet-important-gem:
Take the Y-belt-idler and place it on the front plate. Note there is a mark (circle) on the printed part facing up.
I put the key sentence in bold.
Yeah, so 3(?) years ago, I installed the idler wrong (upside-down). And the "intermittent" noise was likely stress on THAT bearing. So now I do believe the noise is a failing bearing, just not the one I initially thought.
After 1500+ hours of print time, like that, I think it is safe to say I need to replace that pulley's bearing.
my dear a blond or rather a bald moment... 
Looks like there are more fundamental issues with the design here...
