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martin.m25
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Fan noise printing PETG still unsolved?!

Dec 08, 2018 5:01 pm

Fan "whine" from the cooling fan when printing PETG has been a problem from the beginning. If you google for "prusa fan noise pet" you will find that many users have reported this. The root cause is the 470 Hz PWM frequency of the fan control, which is nearly at the most sensitive https://en.wikipedia.org/wiki/Equal-loudness_contour point of the human ear.
I think it has been discussed to death and find it strange that the support seemlingly still sends out spare fans (which changes nothing), although the root cause is in the software. You can find a lengthy discussion on Github:
https://github.com/prusa3d/Prusa-Firmware/issues/460

So.
  • When printing PET, the fan is set to 30%, causing a horrible noise
  • This has been known for almost a year
  • The root cause is known nearly as long
  • Possible software improvements have been suggested, tried out and work
  • There's even a pull request on Github.
HELLO PRUSA, where are you? When will you please fix this bone-piercing awful noise when printing PETG?

I hope that developers won't abandon the MK3 with so many new products coming up.

- Martin

jbinfl
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Re: Fan noise printing PETG still unsolved?!

Dec 09, 2018 1:50 am

Martin:

I do not know about the 30% noise, but I find that I can hear the fan when it is running despite what % it is at. it is not that annoying, but I am a bit older an my hearing maybe degraded to a point where it is not that annoying, but can see where a younger person could be bothered if they can hear it more

After a print ends, I run the fan at 100% (255 = max) to cool the hotend down when done printing for the day and I hear it. It is a fan, but it is not that bad in the grand scheme of things for me...

I ask, is there a fan that does not make a noise when running that could be an alternative? I do not know and am asking. It could be a $$ factor, or maybe all the fans make a noise???

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bobstro
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Re: Fan noise printing PETG still unsolved?!

Dec 09, 2018 2:34 am

If harmonic bothers you at 30% what happens at 29% or 31%? Seems an easy fix. PWM will always make some noise, but you can very easily tweak the settings. What's with all the drama?
My notes and disclaimers on 3D printing and miscellaneous other tech projects
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curtis.c2
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Re: Fan noise printing PETG still unsolved?!

Dec 09, 2018 4:39 am

bobstro wrote:
Dec 09, 2018 2:34 am
What's with all the drama?
indeed. best part is how the fan at full speed is easily twice as 'loud'.
https://www.youtube.com/watch?v=Rf2mNBXZXNA

yes, its slightly annoying, but honestly gets drowned out by everything else in the workshop. are you printing next to your bed at night or something?

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martin.m25
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Re: Fan noise printing PETG still unsolved?!

Dec 09, 2018 1:04 pm

jbinfl wrote:
Dec 09, 2018 1:50 am
Martin:

I do not know about the 30% noise, but I find that I can hear the fan when it is running despite what % it is at. it is not that annoying, but I am a bit older an my hearing maybe degraded to a point where it is not that annoying, but can see where a younger person could be bothered if they can hear it more

After a print ends, I run the fan at 100% (255 = max) to cool the hotend down when done printing for the day and I hear it. It is a fan, but it is not that bad in the grand scheme of things for me...

I ask, is there a fan that does not make a noise when running that could be an alternative? I do not know and am asking. It could be a $$ factor, or maybe all the fans make a noise???
The cooling fan running at 100% is not a problem. But if you print PETG, it runs at 30% only, which is implemented as 470 Hz PWM. Its this PWM frequency that causes the noise. Does probably not matter if you set 20% or 50%. Only silent settings are 0% and 100% (well not totally silent, but OK IMO).
I am printing in my appartment mostly over night so this is an issue.

- Martin

karl.w2
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Re: Fan noise printing PETG still unsolved?!

Dec 13, 2018 1:06 am

I agree with Martin. While it isn't as bad for me since my printer is in an enclosure, I can still easily hear the PWM whine from outside the room. It would be nice to have the frequency changed so that it can't be heard. It is much louder than the noise caused by the fan moving air. MUCH louder.

charles.h13
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Re: Fan noise printing PETG still unsolved?!

Dec 13, 2018 1:47 am

I get a similar fan acceleration with PETG. It works so I am not too alarmed.

ButterworthDesign
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Re: Fan noise printing PETG still unsolved?!

Dec 13, 2018 11:39 pm

karl.w2 wrote: I agree with Martin. While it isn't as bad for me since my printer is in an enclosure, I can still easily hear the PWM whine from outside the room. It would be nice to have the frequency changed so that it can't be heard.
martin.m25 wrote: But if you print PETG, it runs at 30% only, which is implemented as 470 Hz PWM. Its this PWM frequency that causes the noise. Does probably not matter if you set 20% or 50%.
You can set your own fan speeds (and save them as part of your own custom setting) in Slic3r PE. It's found under the Filament tab, in the Cooling page. 5% up or down isn't going to make a significant difference in cooling on the filament or part; you can play with these settings to your heart's content and find a rate that doesn't hit the harmonic on your fan.

Edit: See here for the setting to change during slicing.
Slic3rPE_FanSpeeds.png
Slic3rPE_FanSpeeds.png (37.54 KiB) Viewed 95 times

Edit 2: Also, just curious - does the fan noise go away if, while printing something, you go into the "Tune" menu on the printer itself and adjust the fan speed manually during the print? I only ask because my printer had a very distinct squeak during retract/deretract while printing PETG caused by friction, but this sounded different than what you were describing. It was higher pitched and sounded exactly like PETG rubbing against other PETG (like a box of disposable water bottles in the back seat of a car). That was unrelated to the fans though, and was fixed by remodeling and reprinting the top half of the extruder.

zoltan.f2
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Re: Fan noise printing PETG still unsolved?!

Dec 14, 2018 7:55 am

My is "whining" also on PETG. When I first printed in PETG I thought that the fan is broken.

And no, setting the speed higher or lower does not help much. The sound frequency is a bit different, but it's still very annoying. How annoying you might ask? You can't be in the same room. I'm not kidding you, after 5 minutes of this I hear ringing for another 1/2 hour. I usually setup the print, watch the first layers go down and when the fan turns on I just leave and close the door.

And please don't say such things as "what's with all the drama". I'm personally fine with this, I can bear it, I came to accept it as a cost of using this printer with PETG (I basically only print with PLA and PETG). I also think that probably it's not that trivial to fix since Prusa did not do it by now (and I googled it and it's like a more or less known problem since the Mk3 release). However that does not mean that ppl should not give their input and raise the their concerns from time to time. Maybe in the future some kind of a software solution could be found (such as using a different PWM freq. as someone proposed) that would make this printer even better.

Thank you!

ButterworthDesign
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Re: Fan noise printing PETG still unsolved?!

Dec 14, 2018 8:08 am

zoltan.f2 wrote: My is "whining" also on PETG. When I first printed in PETG I thought that the fan is broken.
That's certainly odd. I'm afraid my experience differs (after addressing a filament-on-extruder plastic friction point), and my printer sounds exactly the same with PETG and PLA (and ABS for that matter). I print about 50% of my prints in PETG, and I am able to sit next to my printer (in a lack enclosure) for several hours at a time.

Just a curiosity point: does the fan "whine" go away if you bend or flex the fan casing slightly in any direction? I was able to produce a mid-range (think middle-C on a piano) pitch by forcing the fan casing in such a way that the blower began vibrating or rubbing on something. If you find something like this, using an extra shim on one of the mounting screws (between the fan body and the printed part) may help twist the fan body back into a good alignment.

Edit: I listened so some of the videos posted on the github page linked above. When PWM is being utilized (i.e., fan is not at 0% or 100%) to control fan speed, my fan does indeed sound like what's captured those videos. I don't find in bothersome, and the sound is certainly a common characteristic of PWM controlled fans.

It's worth noting that the sound isn't related to printing PETG, except in that the filament type prefers something less than 100% fan rate. The way I read this post originally, it seemed as if PETG was directly the culprit here.
Last edited by ButterworthDesign on Dec 14, 2018 8:20 am, edited 1 time in total.

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