Frequently when I want a higher quality print, or if I don't need the print quickly, I usually adjust the feed rate modifier value to something less than 100 in order to reduce vibration and variation.
I've always had problems with stringing for various reasons, but it seems worse when I run Feed Rate Modifier at a low/lower setting.
Does this setting adjust all axis feed rates in proportion? If so, I'd expect the extruder and retraction speeds would also be adjusted. While this would be proper for normal extrusion, it occurs to me that the retraction speed should remain at the unmodified speed as specified by the slicer settings (unless firmware retraction is used).
What did you already try to solve it?
Nothing yet, however if retraction speed is reduced in proportion, I can adjust the slicer speeds in a new profile.
I think this will be firmware dependent how it's handled. There is the difference between feed and flow rate, which are both adjustable from the control tab of OctoPrint.
I'm afraid that you don't understand how Marlin firmware and a slicer works.
Marlin has features, if enabled, to do retraction by firmware. In my limited travels I've not seen any printers yet that have firmware retraction enabled, but that doesn't mean they aren't out there.
Typically, the retraction is done by the settings in the slicer. For example, Simplify3D has setting to control the retract speed, Z lift, retraction distance, wipe distance, coast distance, and retraction restart distance.
When the slicer calculates the speed for motion and extrusion it uses the settings of the slicer. When Octoprint is set to alter the speed of the print, motion and extrusion rates are adjusted. However, if the retraction speed is also adjusted in kind with the motion and extrusion Feed Rate Modification, then retraction would not happen at the speed it should to eliminate ooze & stringing.
My question is meant to determine how Octoprint handles retraction speed when Feed Rate Modification is set to something other than 100.
This is quite rich towards one of the largest contributors to the community, coming from the person who was asking for help. Quite unnecessary in my opinion.
I'm going to agree with @jneilliii here. It would be firmware dependent. All OctoPrint does when it sets the feed rate or flow rate is send a gcode command to the printer, either M220 or M221. In Marlin, and as far as I know other firmware, this is applied linearly across all the axes (inlc. E). It is not OctoPrint applying the speed change, it is your printer firmware.
Thank you for answers my question.
There was no disrespect intended!
The answer provided simply was not complete enough. Of course the firmware "handles" the speed, but it does so by way of the G-code command. Perhaps my question should have been a little more direct as maybe "How does Octoprint handle the speed?"
Octoprint just sends the new feedrate to the printer and the printers firmware speeds everything up or down according to it.
All speeds will be modified - travel, printing, retract, z-hop etc.
I can't tell you whether or not that also affects firmware retraction. I would ask that question in the marlin discord.
So the best solution would be to use slower speeds in your slicer.