Plastics Extrusion - Pipe, Film & Profile worked example

Die Swell Allowance with expected extrudate size at die exit of 2.7 in: a worked example

What does the result look like when expected extrudate size at die exit reaches 2.7 in? The full calculation is worked below with real intermediate numbers. Use it when tooling, process engineering, or quality needs a quick die swell allowance for pipe, profile, sheet, or film dimensions.

The inputs for this scenario

  • Expected extrudate size at die exit: 2.7 in (raised for this scenario; the documented default is 1.08)
  • Target finished part size: 1 in (unchanged)
  • Reference dimension for percent: 1 in (unchanged)

Working through the calculation

  • Applying the documented formula (Allowance = expected extrudate size - target finished size) to the inputs above produces each figure below.
  • At this operating point the engine returns 170 % for die swell allowance, the number this scenario is built around.
  • At this operating point the engine returns 1.7 value for size difference.
  • At this operating point the engine returns 2.7 value for expected extrudate size.
  • At this operating point the engine returns 1 value for target finished size.

How this compares with the baseline

  • Against the tool's baseline example, where expected extrudate size at die exit sits at 1.08 in and the headline result is 8 %, this scenario comes in 2,025% above the baseline at 170 %.
  • A figure at this level is achievable when expected extrudate size at die exit is genuinely sustained, not just peaked for a shift. Swell is highly sensitive to resin, melt temperature, shear rate, and draw ratio — a percent measured on one condition will not transfer cleanly to a different material or line speed.

Results at a glance

  • Die swell allowance: 170 % (headline result)
  • Size difference: 1.7 value
  • Expected extrudate size: 2.7 value
  • Target finished size: 1 value

Run it with your numbers

  • Every input above is editable in the live Die Swell Allowance calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.