Set all speeds as percentages of max volumetric speed #2253

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MrUnknownDE · 2026-04-06T02:28:08+02:00

MrUnknownDE commented

2026-04-06 02:28:08 +02:00

Originally created by @ngolshan on 9/8/2025

Is there an existing issue for this feature request?

I have searched the existing issues

Quality and accuracy of bridges, overhangs, small perimeters, and short-layer-time regions are all dependent on how fast you can cool your filament, and therefore more strongly related to volumetric rate coming out of the nozzle than anything else.

If i know my part fan cools a 50 degree overhang pretty well at around 60% of my max volumetric rate, that's going to be roughly consistent across layer height and extrusion width. The linear (mm/s) speed of the nozzle that corresponds with that 60% of max flow will change dramatically with layer height and extrusion width, though.

Additionally, if using Arachne slicing, width changes all the time, and therefore speed will need to change to keep flow constant!

(Cooling performance will change a little bit with really thin or thick layers, but physics says the mass flow rate of hot filament out of the nozzle and mass flow rate of ambient air out of the part fan will dominate how fast you can print a good overhang or bridge overall.)

The same extruder and part fan will print infill and non-overhang perimeters at max volumetric flow rate just fine.

I'd rather just control the mass flow rate directly. That's fundamentally all we're doing with setting linear speeds anyway, it just requires me to do math based on layer height and width to figure out what i'm doing in terms of flow rate.

Which printers will be beneficial to this feature?

All

Describe the solution you'd like

I want to be able to set speeds for all extrusion types as percentages of maximum volumetric flow rate, as set in either the printer profile or filament overrrides.

I've attached an image as an example.

Describe alternatives you've considered

No response

Additional context

This functionality appears to exist in both Prusaslicer and Superslicer currently.

*Originally created by @ngolshan on 9/8/2025* ### Is there an existing issue for this feature request? - [x] I have searched the existing issues ### Is your feature request related to a problem? Quality and accuracy of bridges, overhangs, small perimeters, and short-layer-time regions are all dependent on how fast you can cool your filament, and therefore more strongly related to volumetric rate coming out of the nozzle than anything else. If i know my part fan cools a 50 degree overhang pretty well at around 60% of my max volumetric rate, that's going to be roughly consistent across layer height and extrusion width. The linear (mm/s) speed of the nozzle that corresponds with that 60% of max flow will change dramatically with layer height and extrusion width, though. Additionally, if using Arachne slicing, width changes all the time, and therefore speed will need to change to keep flow constant! (Cooling performance _will_ change a _little_ bit with really thin or thick layers, but physics says the mass flow rate of hot filament out of the nozzle and mass flow rate of ambient air out of the part fan will dominate how fast you can print a good overhang or bridge overall.) The same extruder and part fan will print infill and non-overhang perimeters at max volumetric flow rate just fine. I'd rather just control the mass flow rate directly. That's fundamentally all we're doing with setting linear speeds anyway, it just requires me to do math based on layer height and width to figure out what i'm doing in terms of flow rate. ### Which printers will be beneficial to this feature? All ### Describe the solution you'd like I want to be able to set speeds for all extrusion types as percentages of maximum volumetric flow rate, as set in either the printer profile or filament overrrides. I've attached an image as an example. <img width="668" height="558" alt="Image" src="https://github.com/user-attachments/assets/167feaa2-d23c-465f-9027-5cead56f452f" /> ### Describe alternatives you've considered _No response_ ### Additional context This functionality appears to exist in both Prusaslicer and Superslicer currently.

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Due Date

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Dependencies

No dependencies set.

Reference: github/OrcaSlicer#2253