Fan advance

ÖrjanE

When the part cooling fan speed is changed during a print, it can take several seconds until the actual RPM is reached since the fan itself has to accelerate/decelerate. When printing a perimeter bridge, for example, this often means that the extra cooling aimed for the bridge actually arrives when the nozzle has long passed the bridge area.

Would it be possible to change the PWM-signal ahead of time, somehow bypassing the movement queue? Ideally, there would be a settable advance time.

A more "scientific" approach might be to have some sort of PID-model for the fan+air plant, but this is probably overkill. Nevertheless, it would still require the M106 gcodes to be processed ahead of the regular movement queue.

MintyTrebor

@örjane You may find this is achievable in your slicers settings, for example in Super Slicer:

which effectively does what you are asking.

ÖrjanE

@mintytrebor Yes, asking the slicer to insert the fan speed command earlier in the gcode stream is an alternative. I do not think PrusaSlicer or Cura have this option (yet). Nice to see that SuperSlicer has implemented this.

Phaedrux

@örjane said in Fan advance:

I do not think PrusaSlicer or Cura have this option (yet).

Cura does for sure. Though it's likely hidden by default.

I thought Prusa Slicer did as well, but I haven't actually used it in quite a while.

ÖrjanE

@phaedrux said in Fan advance:

Cura does for sure. Though it's likely hidden by default.

I rarely use Cura, so it may simply be my inability to navigate the interface, but I do not find this option. Do you know what it is called?

Phaedrux

Sorry, I was mistaken, the fan speed look ahead is only a feature of Cura master build, not mainline Cura. They call it Cooling fan lag.

https://github.com/smartavionics/Cura/releases/tag/20220111

ÖrjanE

@phaedrux Thanks. Perhaps we can hope that this feature will eventually come in the majority of slicers.

I noted that this had also been proposed for Klipper, but never implemented.