[Clarification] Cura Slicer - Volumetric Max Flow Rate and Max Print Speed

[lollo1188]

Hey @AndrewEllis93 ,
this issue has emerged since I want to understand how to use the volumetric Max Flow Rate, in order to know max print speed in slicers like Cura, which do not contain such parameter as other slicers mentioned by this awesome guide.

I understand that the Max Flow Rate needs to be calculated via this method considering temperature, material and nozzle size, but I'm still not sure how to correlate and find a proper max print speed in Cura.
I try to use an example.
Let's say my Max Volumetric Flow is 22 mm^3/sec, and I want to use this formula to calculate Max Print Speed using this formula
speed = volumetric_flow / layer_height / line_width and assume that I use 100% flow/extrusion multiplier, 0.4 line width and 0.2 layer height

I think that, since layer_height and line_width are not what I see here on the slicer parameter, but what is effectively calculated by the slicer itself, called layer thickness and line width, the print speed calculation shall be done as follows:
(consider I can see the values in the preview page, respectively under "Layer Thickness" and "Line Width" tabs)

22 mm^3 sec / 0.20 mm / 0.53 mm = approx. 207 mm/sec
If my calculations are corrects, I think should recalculate the max print speed each time I change something in Cura slicer that modify these two values

Instead, if I use the formula with slicer parameters, considering also other available profiles for PLA, there is a significant difference in print speed:

22 mm^3 sec / 0.20 mm / 0.40 mm = 275 mm/sec
22 mm^3 sec / 0.16 mm / 0.40 mm = 343 mm/sec
22 mm^3 sec / 0.12 mm / 0.40 mm = 458 mm/sec
22 mm^3 sec / 0.28 mm / 0.40 mm = 196 mm/sec

I also send you screenshots of what I see in Cura.

[lollo1188]

I think I'm finding some news about the calculated values.
The settings that are listed in Layer Thickness and Line Width are different values, selecting by opting in/out the checkboxes. Especially for line width, in Cura 5 there is this new feature called variable layer height
(https://support.makerbot.com/s/article/1667417421589)

If I look for example to Shell checkbox, i see this in the various Tabs for this specific model and profile (0.4 mm line width and 0,2 layer height):

• Layer Thickness is 0.2 mm
• Line Width both 0.37 mm (small parts) and 0.53 mm (bigger parts)
• Speed 16.07 mm/s (small parts) and 96.26 mm/s (bigger parts)
• Flow (which is a tab for Volumetric Flow Rate) 1.29 mm^3/s and 7.20 mm^3/s (small and bigger parts)

I've also find this article, related to Flow Preview, that also reports the setting Flow Equalization Ratio

Ultimately, I've also found this plugin for Cura that adds Maximum Flow as a direct parameter, which I want to experiment with.
Consider that in the version Ultimaker Cura 5.7.2 I had to disable bundled plugin "Gradual Flow" in order to let Valve plugin have effects, at least on Preview section, as I have not already tried it.

I do not know if that is useful for the issue