Slic3r 1.40: Max volumetric speed relation to nozzle size, perimeters & layers & speed
I've been working with Slice3r lately, and noticed that I was able to get a good print using Colorfabb XT-CF20 on the 1st try with the supplied filament profile. Working with other slicers, I expected to spend some time figuring out usable speed and temperature settings. The print was near-perfect, although it printed slowly. I realized the Filament Settings->Max Volumetric Speed was set to 1 for this filament, versus 15 for PLA and 8 for PETG.
If I've understood this correctly, I can create profiles under Print Settings for quality, then set per-filament flow restrictions. If so, this is the simplest solution I've found with any of the slicers I've tried (Cura, Simplify 3D, Slic3r).
Yes, you can save a new profile for that filament settings. I have my own for all filaments, particularly for adjusting the extrusion multiplier. And I want to control any changes. I just look to Prusa default profiles from time to time to see if a change interest me.
That said 1mm3/s is very very low. Don't know why it is so low. It is mitigated by the min print speed of 15mm/s. All your print may be at that speed. I use a lot of XT and I set it to 10 but perhaps I will go to the default 8. I have no experience with XT-CF20 but in ColorFabb printing advises for speed are the same, then I would report an issue there: https://github.com/prusa3d/Slic3r-settings/issues . Setting the volumetric speed for XT-CF20 to 8 is logic.
Your maximum volumetric speed limit will be the same no matter what your layer height and
nozzle diameter extrusion width are. Volumetric speed is how fast filament is moving through the nozzle.
Volumetric Speed = <Layer Height> * <Extrusion Width> * <Feedrate>
If you want to find your max feedrate you can move things around to get Feedrate = <Max Volumetric Speed> / (<Layer Height> * <Extrusion Width>). So with a max volumetric of 8mm^3/s, layer height of 0.2mm, and .45mm extrusion width (0.4mm nozzle), your max speed for any print moves is 88.89mm/s.
[...] If you want to find your max feedrate you can move things around to get Feedrate = <Max Volumetric Speed> / (<Layer Height> * <Extrusion Width>). So with a max volumetric of 8mm^3/s, layer height of 0.2mm, and .45mm extrusion width (0.4mm nozzle), your max speed for any print moves is 88.89mm/s.
That's what I'd understood. I have been spending a lot of time trying to calculate meaningful maximum speeds for Cura and Simplify 3D. Realizing this setting in Slic3r over-rode any desired speeds really was a breakthrough. I'm setting speeds as desired maximums, but trusting the max extrusion rate to cap them where necessary. This has really made life a lot simpler. Thanks!