Speed-dependent extrusion: can it be accounted for?

[dewi-ny-je]

In the past I noticed how printing at 8 mm³/s with my hot end caused thinner extrusion width than expected along long straight walls or infill. Now I find this video demonstrating scientifically the phenomenon.
https://youtu.be/0xRtypDjNvI

I have two questions:

1. can it be compensated in Klipper with a speed-dependent extrusion multiplier? As seen in the video, the calibration would be quite simple!
   Also, the faster we print, the bigger the difference between high speed segments and low speed segments is, and the bigger the difference in the effective extrusion. A speed-dependent extrusion multiplier would improve quality by a significant amount.
2. since the pressure advance is calibrated using a tower which, as suggested, should be printed at relatively high speed, would the lack of correction affect the accuracy of the pressure advance calibration as well? Or in opposite way, would such a compensation improve the uniformity of the pressure advance compensation at different speeds?

[klipper-gitissuebot]

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[alfrix]

More info:
https://reprap.org/wiki/G-code#M592:_Configure_nonlinear_extrusion
https://forum.duet3d.com/topic/5588/non-linear-extrusion
First implementation of this:
Duet3D/RepRapFirmware@1ecf339

[GarthSnyder]

I've wondered about this issue as well. It's not a minor difference, either - I've notice that the actual length of 100mm calibration extrusions varies by as much as 40mm depending on the extrusion speed.

[dewi-ny-je]

Well the gear gripping the filament always has some degree of slipping. The more the counter pressure, the higher the slip.

While 40% seems a lot to me (maybe the filament is not squeezed tight enough by the driving gear and counter-bearing), correcting for this progressive slip would be welcome. It should be probably linked to the pressure in the nozzle already known to Klipper.

[KevinOConnor]

It would require an interested developer to implement this. It should only require Python host changes (not micro-controller code changes).

-Kevin

[KevinOConnor]

I'm going to close this as it looks like the original question was answered (it's possible but would require an interested developer to implement it).

-Kevin

[dewi-ny-je]

But if it's closed, how will a developer see it? Isn't it better to leave it open for some months for better visibility?

[yschroeder]

I just learned that RepRapFirmware implemented this:
https://duet3d.dozuki.com/Wiki/Gcode#Section_M592_Configure_nonlinear_extrusion