Queendom Tools

Extruder Drag Flow Calculator

For extrusion engineers who need a fast first-pass check on metering-zone throughput for a new screw design or a speed change before committing to a full non-isothermal 2D screw simulation. This tool computes the isothermal Newtonian metering zone drag flow, based on the formula: Q = 0.5 * pi^2 * D^2 * N * h * sin(phi) * cos(phi).

Volumetric Drag Flow Q:
— cm³/s
Disclaimer: For preliminary estimation only, not a substitute for review by a qualified/licensed engineer. Assumes zero pressure gradient (pure drag flow, Newtonian, isothermal).

How to Use This Calculator

  1. Enter the screw diameter D in mm.
  2. Enter the metering channel depth h in mm.
  3. Enter the screw speed N in rpm.
  4. Leave the helix angle at 17.66° for a square-pitch screw, or type your actual flight helix angle in degrees.
  5. Optionally enter melt density in g/cm³ to also read mass throughput in kg/h.

FAQ

Q: What is the drag flow equation for a single-screw extruder metering zone?
A: Q = 0.5 · π² · D² · N · h · sin φ · cos φ, where D is screw diameter, N is screw speed in rev/s, h is channel depth and φ is the helix angle — the isothermal Newtonian drag-flow term.
Q: Why does the helix angle default to 17.66 degrees?
A: 17.66° is the helix angle of a square-pitch screw, where the flight lead equals the diameter: tan φ = D/(π·D) = 1/π, so φ = arctan(1/π) ≈ 17.66°.
Q: Does this calculator include the pressure (backpressure) flow term?
A: No. It assumes a zero pressure gradient, so it returns pure drag flow. A real screw's output is the drag flow minus the pressure-driven backflow generated by the die and screen pack.
Q: How do I get the throughput in kg/h instead of cm³/s?
A: Enter melt density in g/cm³; the tool multiplies the volumetric rate in cm³/s by density and by 3.6 to convert to kg/h.