Constantly and Quickly Surging Fans
 
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jackmanbob
(@jackmanbob)
Member
Constantly and Quickly Surging Fans

Hi, all! I'm hoping someone can help me out here, or at least confirm that what I've found is a legit bug with Prusa Slicer?

Recently, I've been having trouble with my fans surging from 20% to 100% repeatedly at a very high frequency (8900 speed changes within a basic 90 minute print, averages to 1.6 speed changes _per second_). It seems like might be somehow related to dynamic overhangs, but even dynamic print speeds has no effect (on the fan bug). Disabling dynamic fan speeds, the gcode improves very slightly, but the problem persists.

Below is an image of the part I'm printing (the smaller part has a 45* overhang, but (pretty sure) the fan problem persists when printing layers above that, too)

Also a screenshot of my overhang-related settings and a snippet of resultant g-code.

The very last image is the "improved" gcode after disabling dynamic fan speeds, but you can see the pulsing/surging is still present.

Any info or suggestions you might have are appreciated, and please let me know if I can provide any more info about my setup!

Part Image

Print Settings

Fan Settings

GCode Dynamic ON

GCode Dynamic OFF

This topic was modified 11 months ago by jackmanbob
Posted : 02/12/2023 1:27 am
TheMicke
(@themicke)
Member
RE:

Similar problem here slicing this test file https://www.printables.com/de/model/342481-overhang-test-regular with 2.8.0 and dynamic fan speeds enabled.

example of fan speed changes, in total I get 18069 fan speed changes on a 15min print

I tried different settings this is what I'd want to realize:

overhang test newV6(1).gcode

example:

G1 F1913.824
M106 S122.4
G1 X148.525 Y135.617 E.0096
M106 S94.35
G1 F1630.309
M106 S142.8
G1 X148.983 Y135.275 E.01018
M106 S94.35
G1 F1491.463
M106 S153
G1 X149.475 Y135.1 E.0093
M106 S94.35
G1 F1486.389
M106 S132.6
G1 X150.152 Y135.053 E.01209
G1 X150.392 Y135.094 E.00434
M106 S94.35
G1 F1650.72
M106 S135.15
G1 X150.872 Y135.213 E.00881
G1 X151.254 Y135.423 E.00777
M106 S94.35
This post was modified 3 months ago 3 times by TheMicke
Posted : 08/08/2024 7:06 pm
_KaszpiR_
(@_kaszpir_)
Honorable Member
RE: Constantly and Quickly Surging Fans

Try lowering Fan Settings > Bridges Fan Speed? It is 100% on those screenshots.

Otherwise report on GitHub.

See my GitHub and printables.com for some 3d stuff that you may like.

Posted : 08/08/2024 7:58 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Constantly and Quickly Surging Fans

Already open issues on GitHub about excessive amounts of fan speed commands. A couple of them at least iirc. Don’t have time to search at the moment for the exact links but go add to them. 

Posted : 09/08/2024 4:41 am
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