Flow Rate
Extrusion multiplier — fine-tunes the volume of plastic deposited after E-steps are calibrated. Compensates for filament diameter variation and material compressibility.
Critical priority
Filament-Specific
What It Is
Flow rate (extrusion multiplier) is a percentage adjustment applied on top of E-steps calibration. Where E-steps ensure the extruder pushes the right length of filament, flow rate compensates for the fact that different materials, diameters, and nozzle geometries produce slightly different actual deposit volumes.
What It Controls
- Wall thickness accuracy
- Top surface quality (gaps vs. over-fill)
- Dimensional accuracy
- Layer bonding (related to squish)
Why It Varies
- Filament diameter variation (1.75mm ± 0.05mm is common)
- Material compressibility (TPU compresses more than PLA)
- Die swell characteristics differ by material
- Nozzle wear changes orifice size
How to Calibrate (Manual)
- Print a single-wall cube (vase mode or single perimeter)
- Measure wall thickness with calipers
- Calculate:
new_flow = current_flow × (expected_wall / measured_wall) - Adjust in slicer (typically 90-110%)
- Reprint and verify
How the Auto-Tuner Calibrates It
- Inline filament diameter sensor measures real-time diameter variation
- Weight-based method: weigh extruded filament vs. expected weight
- Roller encoder monitors actual vs. commanded feed for slip detection
Related Anomalies
- Under-extrusion — flow too low
- Over-extrusion — flow too high
- Elephant Foot — over-flow on first layer