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Gah! Help me ID this noise...  

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vintagepc
(@vintagepc)
Gah! Help me ID this noise...

Printer started making a terrible racket today during a particular travel move for a print.

https://vimeo.com/394824890

Hopefully someone with an experienced ear knows what's up... I cannot figure it out, but not for lack of trying. It is not always consistent, sometimes it's very loud, somtimes not at all, and sometimes in between.

If you think that a bearing has crapped itself... yeah, I'd agree it sounds like that... except, here's my ace in the hole: I have vesconite bushings on both axes. 

Things I've tried/checked:

  • Reproducing the noise with the same travel move in pronterface. No luck, printer is silent/behaving. (but it does it consistently with this print)
  • Checked for loose bolts, nuts, whatnot. Everything was tight. 
  • Axes feel normal, not binding anywhere.
  • Rods are not dry, they have a thin film of lubricant on them.
  • Printer is isolated from the LACK soundboard table with sorbothane, feet, sitting on top of a marble cutting board (which has its own hard rubber feet).
  • Head is not dragging over infill, given the print nature (Z-hop is 0.3)
  • LCD (another common culprit) is mounted to the front of the LACK table, not on the printer.
  • I feel the vibrations on the printer frame when it happens.

What gives? 

 

Posted : 01/03/2020 11:50 pm
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(@)
Illustrious Member
RE: Gah! Help me ID this noise...

Might be the printer is running at a speed in which the drivers are setting up a harmonic in one or both motors.  It would be useful to ferret out the line in the gcode for that move and start trouble shooting from there.

 

Rereading, you say you've tried the same move: was it the 'exact same move" X Y and Z params?   Make sure the bed is at temp, too. And watch for heater ON versus OFF ...

This post was modified 2 years ago 3 times by --
Posted : 02/03/2020 3:29 am
vintagepc
(@vintagepc)
Topic starter answered:
RE: Gah! Help me ID this noise...

Yeah, I did try the same XYZ (and F) line from the g-code. bed and hot end were not at temp, may have to try it with that... 

 

 

Posted : 02/03/2020 12:14 pm
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(@)
Illustrious Member
RE: Gah! Help me ID this noise...

What I am thinking, and it's a way-out-there possibility, is that the move, combined with other loads, get the motor drive currents and voltages to that sweet spot where things inside the motors take off. A resonance point.   My printer will do something similar, out of the blue, not repeatable, and annoying as heck when it happens.  Always a diagonal, sounds like something on the bed itself is rattling, and pulling up on the front of the sled seems to quiet things a bit; but I can't say it is the lifting or a touch more load on the drive.    And, it was my impression the effect changed when Prusa was mucking with driver currents - at one rev is was a lot worse - but a later rev is got a bit better, but still not as quiet as the original firmware the printer came with. 

The worst part is the bed is a great sounding board. Noise from the motors, the bearings, stuff inside the extruder, all bounce off it: so the noise could be coming from most anywhere.  

Posted : 02/03/2020 8:07 pm
vintagepc
(@vintagepc)
Topic starter answered:
RE: Gah! Help me ID this noise...

Yeah, definitely annoying since it sounds like the printer is about to seize up or something. I need to run a few more copies of that print anyway, let me try once and see if it goes away when running in normal mode (I typically run stealth)

I agree that since the usual culprits have been eliminated, the only thing that remains is a resonance of some kind. I occasionally do get a very annoying one during Z travel from tall places as well. I've contemplated just bolting a spare stepper onto the frame somwhere for extra mass damping - with the hope it bumps the resonant frequency out of the normal operating range of the printer.

Posted : 02/03/2020 8:17 pm
gnat
 gnat
(@gnat)
Noble Member
RE: Gah! Help me ID this noise...

You said you have the bushings on two axis, which two? 

Since I'm not printing much any more I get a similar sound from a similar move after my printer has sat for awhile. I've chalked it up to my Y axis as it still has bearings and the problem goes away after a few prints that use a good portion of the Y travel. My theory is that due to sitting and it being fairly cool in my office that the grease is hardening and drying a bit and after moving things around for awhile the grease warms up and re-lubes everything properly. I've also noticed that it is more prominent with faster moves, but it's still there for slower moves if I listen carefully.

I think Tim is also correct that since it is pretty limited to that "diagonal" move that it a harmonic issue more than a true grinding (at least I've seen no sign of damage to my Y rods). YMMV though.

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Posted : 02/03/2020 10:48 pm
vintagepc
(@vintagepc)
Topic starter answered:
RE: Gah! Help me ID this noise...

Both X and Y; Z doesn't bear any significant load so I have not had any issues with rod scoring there, and didn't feel a need to replace.

 

This post was modified 2 years ago by vintagepc
Posted : 02/03/2020 10:56 pm
vintagepc
(@vintagepc)
Topic starter answered:
RE: Gah! Help me ID this noise...

Yeah, definitely seems like resonance. I ran the same g-code in normal mode and it didn't seem to hit that frequency anywhere near as badly. But going back to stealth mode it returns. 

I noticed it seems to come and go with alternating layers... I wonder if this is a combo of the bed and frame as amplifiers, and the ends of the Z leadscrews being free to vibrate. Might be worth making them captive in some 608 bearings for testing to see if it damps - definitely does make a difference if I'm touching them during the move, it's not as harsh a noise anymore.

Posted : 05/03/2020 12:24 am
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