Max Volumetric Flow
The maximum volume of plastic (mm³/s) the hotend can melt and push through the nozzle — the true speed limit for extrusion.
High priority
Filament-Specific
What It Is
Max volumetric flow rate is the maximum volume of plastic (in mm³/s) that the hotend can melt per second. This is the real speed limit — not mm/s travel speed, but how fast plastic can actually be extruded. Exceed it and the extruder grinds, skips, or under-extrudes.
What It Controls
- Maximum achievable print speed (for each line width and layer height)
- Whether the printer can actually keep up with commanded speed
- Under-extrusion at high speeds
Why It Varies
- Hotend design (all-metal vs. PTFE-lined, melt zone length)
- Nozzle diameter (0.4mm vs. 0.6mm vs. 0.8mm)
- Material (PLA melts faster than PETG, which melts faster than nylon)
- Temperature (hotter = lower viscosity = higher flow possible)
- Filament quality (additives affect melt behavior)
How to Calibrate (Manual)
- Extrude into air at increasing feed rates (e.g., 1, 2, 5, 8, 10, 15 mm³/s)
- Listen/watch for extruder clicking, grinding, or visible under-extrusion
- The rate just before failure is your max volumetric flow
- Set as limit in slicer (e.g., PrusaSlicer: Filament Settings → Max volumetric speed)
How the Auto-Tuner Calibrates It
- Roller encoder monitors actual vs. commanded feed rate at increasing speeds
- Detects the point where actual flow falls behind commanded flow
- No test print needed — just extrude into air at increasing rates
Related Anomalies
- Under-extrusion — printing faster than MVF causes starvation
- Grinding — exceeding MVF causes gear to strip filament