Sprue Volume Calculator

Estimate the volume of a tapered circular sprue as a frustum. Use this as a documented planning estimate, then validate it against the actual machine, mold, resin, and process.

Formula and method

Volume = pi x height x (D1 squared + D1 x D2 + D2 squared) / 12.

Take start and end diameters from the CAD sprue geometry, not a nominal nozzle label.

Inputs and units

Use controlled records, CAD, measured production data, the exact resin data sheet, or machine-maker specifications. Keep the material and time basis with the result.

Worked example

A 70 mm sprue from 12 mm to 6 mm is 5.50 cm3.

What the result supports

This result is a first-pass screen for mold geometry planning. Use it to identify the next record or engineering check, not as a release decision.

Sanity check

Check the unit basis and whether all quantities describe the same cavity, shot, machine, or production window before comparing values.

Important limitation

This is only the tapered sprue; add runners and gates separately.

Reference: Autodesk: runner layout.

Next calculation

Runner Volume Calculator

FAQ

What must be checked after using sprue volume calculator?

Retain the input source and compare this estimate with the applicable machine, mold, supplier, or production record before relying on it.