When this setting is enabled, the printer uses this value during printing. The extruder’s PA value is ignored, and printing proceeds using the value from the slicer. The following command appears in the G-code:
Standard print profiles cannot be modified directly—you must always create a copy. Probably, most default values are entirely sufficient for most users. But if the feature exists, why not use it? Otherwise, you can simply disable automatic Dynamic Flow Calibration.
Would it be possible in a future update for the U1 to use its internal PA value if one exists, and only fall back to the slicer’s value if no automatic Dynamic Flow Calibration has been performed?
This is great information that alluded me previously. Thank you for clarifying this for me!!
Not sure if it fixes my problem entirely but it definitely answers a question about what value is actually used at print time. Why do they leave this setting ENABLED on their SnapSpeed filament setting in SnOrca?
One thing I will comment on though is that this setting WAS enabled for me and before and after Flow Calibration the output on my first layer visibly changed and got worse afterwards so it seems like it uses it somehow even with it enabled. Maybe it was a fluke and my results were just worse despite it.
During printing, these values should also appear in the overview under pressure advance. These are almost always multi-digit numbers. If only “smooth” numbers like 0.02 appear, they likely come from the slicer. I’ve tested this multiple times yesterday.
That’s a great note about the even numbers being uploaded from the slicer. That makes a lot of sense. This is some excellent information.
I don’t have time at the moment to do another test with the flow calibration to see it in action but I’ll give it a go tomorrow. At the moment I need to kick something off to print now that I have my printer working again. For the record, the flow settings I’m using for my filament at the moment were arrived at with the Flow Rate YOLO test although that isn’t the same as the Pressure Advanced which I’ve left at 0.02.
Here is a general update regarding automatic extrusion calibration:
Many people assume that during this calibration, the printer determines the material flow ratio—classic values like 1.0, 0.98, or 0.95 that define how much material is extruded overall.
However, this is a common misconception.
In fact, the printer does not calibrate the material flow factor here, but rather the Pressure-Advance value.
Typical values are around 0.02 for PLA and 0.04 for PETG.
The determined Pressure-Advance value is assigned to the currently active extruder.
When the material is unloaded, this value is reset to zero and is no longer active.
Therefore, when inserting a new material, the calibration must be performed again to determine the appropriate Pressure-Advance value for that material and extruder.
Pressure Advance does not affect the amount of extrusion, but rather the timing of extrusion during acceleration and deceleration phases to produce a consistent extrusion pattern.
The material flow factor, on the other hand, solely determines the total amount of material being fed.
Although both parameters affect the print quality, they serve fundamentally different purposes and should not be confused with each other.
I’m not sure if I’m the only one with this problem, but the PA generated by the dynamic flow is grossly off. I usually use the built-in PA line calibration to determine the k value. When i use dynamic flow calibration, the k value returned is grossly different from what my manual calibration values are.
I just posted the same sentiment in another thread, literally right before finding your posting. Do you know what’s measured? Why it would be that much off?
I also conducted a test yesterday with PLA matte. According to the automatic extrusion calibration, it was 0.0169. A manual calibration yielded approximately 0.0175–0.018. I find this value well-chosen. I will repeat this test again with Material4Print PETG deep black.
However, your value deviates significantly—I agree with you on that!
I have now tested the PETG. The automatic calibration resulted in a value of 0.033. Based on the test from the Orca slicer, I would set an optimal value of 0.051.
Agree with you. If I only do a cornering test, that suggests using maybe a 25% higher value. Other tests agree very closely with the U1 though and resulted in slightly better top surfaces.
Okay. This is problematic then. I have noticed that every time it does this calibration, it is always at 250c, regardless of the filament.
EDIT: I am wrong about that. It does the calibration at print temperature. The 250c thing is done whenever loading filament. I think it is a middle ground for purging filaments that want a higher temperature.
I suppose the use of this is advisable when using generic profiles or something for a quick print with a filament that has not been calibrated, but I am thinking that if we are going to chase perfection, then the calibration should not be used and we should stick with the calibration tests in the slicer.
