Volumetric flow: connect deposited area and speed

Speed in mm/s describes motion; flow in mm³/s describes volume per second. Understanding extrusion demand requires the deposited cross-section, which must not be confused with the incoming filament cross-section.

Write the units before calculating

For deposited area A in mm² and speed v in mm/s, Q = A × v in mm³/s. Conversely, a flow limit Q gives v = Q / A in this model. This dimensional relationship is not a hotend measurement.

PrusaSlicer documentation says speed may be reduced when demanded flow exceeds the volumetric limit. It uses a stadium-shaped cross-section and distinguishes print-profile and filament limits. Width × height is therefore only a rectangular approximation, not an exact reproduction of that slicer.

An explicitly approximate example

Assume width 0.45 mm and height 0.20 mm. A rectangular approximation gives A = 0.45 × 0.20 = 0.09 mm². At 60 mm/s, Q ≈ 5.4 mm³/s. At 120 mm/s, Q ≈ 10.8 mm³/s.

None of these values is claimed as a machine capability. Actual extrusion geometry, material and heating conditions are not validated by this calculation.

Read the slicer output

Within one project, compare width, height, requested speed, flow limit and the sliced speed preview. Check units and the active profile before concluding that a setting was ignored. A requested maximum does not mean that speed is reached throughout a path.

Do not confuse volumetric flow and extrusion multiplier. Changing a speed limit does not establish a need to change material quantity. The settings guide provides context.

What this article cannot predict

The calculation predicts neither total duration, quality nor part strength. The analyzer does not reconstruct paths or actual flow. To convert filament length using its own cross-section, use the mass-length guide; that is a different calculation. LayerBench3D has measured no maximum flow rate.