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Can y'all help me understand the various flow settings?



MaterialFlow  (this is the standard flow setting to me. IE, if adjusted here I'm changing the percentage of the 100mm step test? IE, once I've got esteps right to pass 100mm of filament, this is now considered ground zero or 100% ? )

Speed: Flow Equalization Ratio  (the descriptive words mean something to me individually, but big picture? Nope


Finally:   Ender 3v2, how does its flow setting as seen on the screen, which is "tunable on the fly",  affect what the printer g-code calls for? 


Many thanks in advance, PDC

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    Material > Flow: Cura calculates the flow rate based on wall width, height, length and speed. This lets you override it as a percentage of what Cura has calculated. The idea is that if your system is partially clogged or something, you can increase the flow to increase the amount of material being pushed through to compensate, or if your printer is misbehaving and overextruding, you can compensate for that. Some people (myself included) use the option to increase flow rate for the first layer, only a little bit in my case (105%) just to make sure a decent amount of material gets through which helps adhesion.


    Speed > Flow Equalization Ratio: Some printers can take a fraction of a second to change the flow rate after receiving the g-code for it. Depending on the print speed, the head could have moved a few millimetres by the time the flow rate actually adjusts and you get the line width you want, especially if you're using a Bowden extruder (applies to the Ender 3 v2) since there's still the filament in the tube between the feeder and extruder to go through before the adjustment kicks in.

    • Cura can change the speed of the print head to compensate for this, moving faster or slower for a bit while waiting for the flow rate change to take effect so you still get the line width you want. This is 100%, and recommended if you have a Bowden extruder.
    • It can rely entirely on the printer to change the flow rate and not use g-code to compensate at all. This is 0%. I'm still not sure if you want to set it this low even if you have a direct drive extruder.

    It's best to just leave it at the default setting for your printer's profile. If in doubt, increase it, but you should probably leave as is.


    Finally: I have an Ender 3 v2 Neo so I'm not sure if mine works exactly the same as yours, but when I change settings using the screen it does override the g-code, but I haven't tested whether those changes persist if the g-code ever includes an instruction to change it.

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    I can add a little here to what @Slashee_the_Cow said.

    When "Volume of Filament Through the Extruder = Calculated Volume of an Extrusion" then Flow is 100%.

    That's why it's important to calibrate the E-Steps AND to get a good measurement of the actual diameter of the filament (as opposed to just using what it says on the roll).


    1.75 filament is 2.405mm³/mm so if your Layer Height is 0.20 and your Line Width is 0.40 then 2.405/.08 = 30.06mm of extrusion.


    The filament brand I use is consistently 1.72mm diameter.  If I didn't change the number in Cura then I would be consistently under-extruding by 3.4%.


    When you change the Feed Rate on the LCD of the printer, it internally sends M220 to itself.  That will adjust all the  feed rates of the Gcode by the percentage you enter and it will last as long as it is in effect.

    Tuning the Flow works the same way with M221 being used internally.  All "E" numbers coming into the printer are adjusted by the Flow Percentage that you enter.

    If you cycle the printer Off and On then the Feed Rate % and the FLow Rate % are reset.  BUT...If you happen to tune a print to 110% and after it finishes you immediately start another print, the second print would start with a flow rate of 110%.

    So you can see that it's a good idea to have M220 S100 and M221 S100 in your StartUp Gcode.  Every print will then start at 100% flow and feed.


    Finally (since it's Sunday and I haven't had a good Sunday Rant lately)

    Volume of Filament = PI * r² * Length

    Volume of Extrusion  = Layer Height * Line Width * Length

    There is nothing in there regarding a "single wall calibration cube".

    Calibrate the E-steps, measure the filament diameter, and you are done.

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