ISO: Flow setting  

@reddawg

I guess what you looking for is "Extrusion Multiplier" in "Filament Settings" - "Filament"

Printer menu, gcode commands, or PrusaSlicer extrusion multiplier

Do be aware that they do equivalent things, but via different means.

1. Changes made via the printer menu are functionally equivalent to issuing the M221 gcode command. Either method will apply a modifier to any extrusion commands received by the controller. (Note: This setting is NOT automatically reset between prints, and must be reset or the printer power cycled.)
2. Adjusting the Extrusion Multiplier in the slicer (flow in Cura) adjusts the calculations used by the slicer. The extrusion rates inserted into the generated gcode will be adjusted accordingly.

Be aware that these can be combined. If you're tweaking the extrusion multiplier, you can save your sanity by leaving the printer settings (via front menu or Marlin M221 gcode command) alone. I make a habit of resetting M221 to 100% in my startup gcode, removing any other M221 commands from startup gcode, and only making tweaks in the slicer. This makes it easier to do everything in one place.

ISO: Flow setting

Seems to be some inconsistency in terms. This post seems to imply that the flow rate can be set as a percentage in the slicer, however, the "Extrusion Multiplier" parameter in the Filament Settings sub-menu is shown as a dimensionless number where it appears 1 = 100%. Since the default value is "1", I would expect the flow value in the LCD Tune sub-menu would also be 100(%), but apparently the print-starting M221 gcode command (95%) takes presidence, so unless you edit that out, any change you make in the Extrusion Multiplier field will be ignored, and the only other option to change it is the Tune sub-menu. Do I have that right? Consistency please!

RE: ISO: Flow setting

@reddawg

If you change "Extrusion Multiplier" in PS the extrusion rate is changed at g-code level. "M221 0.95" in start-up code is an old relic from the when Prusa printers consistently overextruded. Josef has an explanation Here

Example:
Your E "Extrusion mutliplier" is 1.1, so the g-code that comes out has a flow rate of 1,1
Start up g-code set M221 to 0,95, that means flow rate from the extruder is 1,1 * 0,95 =1,045
If you then turn knob on lcd to 110% you have 1,1*0,95*1,1 =1,1495 out from the extruder.

any change you make in the Extrusion Multiplier field will be ignored

No, nothing will be ignored, it just multiplies along the way from slicer (Extrusion Multiplier) -> startup g-code (M221) ->Flow on LCD-screen.

If you change filament "Extrusion Multiplier" changes affect all prints with that particular filament
If you change "M221" in startup g-code it will affect all prints sliced with that particular printer until the end of time, (at least until you change it next time)
And if you turn the knob on LCD it will affect all prints until power cycle or reset (the X-button), or if you set it back to "100%"

Seems to be some inconsistency in terms.

Yes, I agree, but in the same time it is not really the same thing, sure, the outcome is the same, but changes comes from different level in the process of getting some plastic out of the extruder.

ISO: Flow setting

Thanks for the thorough explanation. 

Printer & slicer settings are unaware of each other

Just to be clear: The flow rate indicated on the printer is only changed by adjustments from the printer menu or M221 gcode commands. It (the printer firmware) is unaware of any slicer settings (and vice-versa). Mixing the two (as Prusa has done with the annoying M221 command in the PrusaSlicer start gcode) causes a lot of confusion.

@bobstro

Ok, my bad 😌, checked my printer and I was wrong
Thank you for sort it out 👍 (and I learn new things every day 😀)

Just a general comment. These settings can be confusing.

Posted by: @ringarn67

@bobstro

Ok, my bad 😌, checked my printer and I was wrong

I didn't mean to point at you specifically. I was very (very very) confused by the M221 in the PrusaSlicer start gcode myself and just wanted to point out a possible trap to others. I would adjust my extrusion multiplier, then "fix" the flowrate on the printer and end up with a mess. Now I go out of my way to ensure the printer is set to 100% via M221 at the start of every job and do all my tuning in the slicer. If I spot an issue and can fix it with the front knob, I update my PrusaSlicer profiles.

I didn't mean to point at you specifically.

No worries, I didn't read it that way 😉 
I read your post and realize that it didn't was in line with my post. I check my printer, and I was wrong.
And I am sort of glad I was, now there is only two places to keep in mind, Extrusion multiplier and "flow", regardless where flow is set from/with.

Now I'm as sure I understand as I was a couple of hours ago 😀 

What about bridge flow, ironing flow and MVS or Volumetric flow rate?

RE: Mostly slicer-specific settings

Posted by: @swiss_cheese

What about bridge flow

Only applies to bridge layers. Slicer only, no corresponding printer menu or gcode command.

ironing flow

Only applies to ironing. Slicer only, no corresponding printer menu or gcode command.

and MVS or Volumetric flow rate?

Slicer limits speed to stay at or below the specified limit. Extrusions will be calculated at the final speed just like any other. Slicer only, no corresponding printer menu or gcode setting (although it should be matched to your actual hotend volumetric rate).

The extrusion multiplier will be applied to calculations based on these numbers in the slicer. Any applied M221 modifier will be applied in the printer and also affect all extrusion types (since the printer has no concept of perimeter versus infill, for example). The printer will only display the M221 value.