Extruder Output Test Calculator

Convert a timed, weighed extrudate sample into kg/h and normalized kg/h per screw rpm.

Formula and method

Output (kg/h) = collected mass (kg) × 3,600 ÷ collection time (s). Normalized output = kg/h ÷ screw rpm.

Inputs and units

Collect discharged material for a timed interval after the line is stable. Weigh only the material represented by that interval and record average screw rpm from the same interval.

Worked example

A 4 kg sample collected in 80 s at 50 rpm equals 180 kg/h and 3.6 kg/h per rpm.

When to use it

Use during a stable output check, feeder verification, screw comparison, or before reconciling extruder output with take-off demand.

How to interpret the result

Compare kg/h per rpm only on a documented material, screw, temperature, head-pressure, and feeding basis. A lower normalized result is a prompt to inspect the record; it is not a diagnosis.

Assumptions and limitations

The result is an interval average. Surging, startup material, diverted scrap, gear-pump behavior, moisture, and scale or timing error can make a short sample unrepresentative.

Validation guidance

Repeat at least three stable intervals, retain each result rather than only the mean, and reconcile total collected mass with the production record.

FAQ

Why normalize the output by rpm?

It creates a useful same-line comparison. It does not make different screws, materials, dies, or pressure conditions equivalent.

Sources

SPE Extrusion Division: Output Calculations · Davis-Standard Extruder Specifications