Knocking noise mystery
I am getting an intermittent knocking noise from my PRUSA i3 MK3S printer. It sounds as if someone is knocking on the build plate with something hard.
I have not noticed any print quality problems. No under-extrusion or over-extrusion as far as my 'novice' eyes can tell. No layer shifts. The noise does not seem to happen with any predictable pattern. I do not think the print nozzle is dragging on the bed (z-height seems good to me). The noise happens with both the powder coated sheet and the smooth PEI sheet.
I have looked underneath the build plate and I do not see anything loose or misaligned under there. I have opened the extruder-idler and I do not see any problems in there. If I had to guess I would say the noise may be associated with Y axis movement, but this really is just a guess???
I have attached a video with a few of the 'knocks' to listen to. Any help would be much appreciated. ThanksIMG_1986
RE: Knocking noise mystery
I get some knocking too, and it sounds like it's from the build plate or below it. But believe it or not, it's from the filament roll spinning on top of the printer. Maybe it's the same for you?
RE: Knocking noise mystery
@mafredri
I am currently printing from a filament dry box (for PETG prints) beside my printer. And yes, you are correct, the dry box makes a fair amount of banging and knocking but I am confident it is NOT the source of the noise in question. I still get the noise when I use the stock PRUSA filament holder (for PLA prints). I feel confident this noise is coming from the area of the print bed. Thank you for your input!
...and as AN UPDATE...
The noise has gotten a little worse while printing today, more frequent knocking. It definitely seems to be related to Y-axis moves, especially when they are fast Y only moves. Still no effect on print quality. When I touched the following things while printing, I do not feel a vibration as the noise happens: Y-axis motor, pulley or belt, frame, Y-axis smooth rods, or the extruder assembly. I believe I am feeling the noise coming from the print bed, or below it more specifically. I am starting to wonder if it could be a Y-axis bearing problem. It has gotten annoying enough that it needs to be solved before I move on. I am breaking out the tools and assembly instructions and going in for a deep diagnostic dive.
RE: Knocking noise mystery
Thanks for your update. Now that you mention it I have also suspected bearings (the filament reel was a convenient explanation though and it does knock, so...).
By the way, the recommendation for bearings orientation has changed recently. Depending on when you assembled your printer, it could be that they are not in the recommended orientation. If you do disassemble, you can compare against the online manual. But I do still have knocking even with the correct orientation so... don’t get your hopes up 😅
RE: Knocking noise mystery
@mafredri
Ok thanks, I will definitely check that out. I assembled my printer in July this year.
Another update on my problem...I discovered that with the printer unplugged, I am able to recreate the 'knock' by sliding the Y-axis back and forth by hand. Nothing seemed loose or knocking on the magnetic heat bed so I have removed that. The Y-axis bearings or their U bolts remain the most likely source of the noise. More disassembly planned for today.
RE: Knocking noise mystery
Problem solved, so far...
I checked my Y-axis bearings and, sure enough, they were oriented as described in the Assembly Manual. Those directions have changed online. So I re-oriented the bearings to the new correct orientation and I also lubricated the smooth rods. Everything is reassembled now and the knocking noise is gone. I pray it stays gone. Thanks again for the tip!
RE: Knocking noise mystery
Checking in here over a year later. I seem to have the exact same Y axis noise your machine exhibited. Since re-orienting the bearings, has the noise returned? I would rather not tear down my Y axis, but understand the necessity. Any tips for someone at the crux of the problem?
RE: Knocking noise mystery
If you take your PEI sheet off the bed and push it in the middle, some sheets might have a little bit of flex in the middle. For me, this was what was making the knocking sound. I wracked my brains to find the source of the noise - worrying that my nozzle was scratching the PEI surface. It all turned out to be harmless sheet flex. It has not affected my prints at all.