Using Max Volumetric Speed with Slic3r Prusa Edition¶
These notes apply to the Prusa i3 Mk3 printer. If you are using a different printer, please verify the hardware details are same. These pages may be a bit rough as I revise them and add new material. Please check back regularly for updates.
Volumetric speed limits are your best friend when using multiple nozzles. You can set your speeds to your preferred settings and the volumetric limits will throttle when and if necessary. I’ve got all my extrusion widths set to 0 so Slic3r Prusa Edition figures them out based on nozzle size. That is working very well, and I’m able to use a single print setting profile across all nozzles except for fine detail work. I’ve got a separate “miniatures” profile for 0.25mm detail work.
Life is a lot more difficult if you’re using another slicer that doesn’t support volumetric limits. You have to set your max speeds to ensure you never exceed the hotend capacity. You have to keep speeds much slower to avoid problems.
The max volumetric speed you should use depends on your hotend. The E3D V6 hotend that ships with the Prusa i3 Mk3 is can process filament at roughly 15 mm3/s, though in practice 11.5 mm3/s is realistic. The Volcano hotend upgrade increases this to roughly 25 mm3/s but does require some printer and software modifications.
Calculating maximum volumetric rates is straightforward:
Max. Volumetric Rate = Layer Height X Extrusion Width X Speed
Individual filaments also affect the amount of material that the hotend can process. Viscocity, content and other characterstics may greatly reduce effective throughput. PETG, for example prints well at a recommend rate of 8 mm3/s.
Much of the time, neither linear speeds nor volumetric throughput matter when doing smaller prints. It’s when you start doing larger parts or moving fast for things like infill that it matters. “Obeying the speed limit” with the volumetric setting avoids extruder clicks and jams.