Plastic extrusion · Production setup
Tube Extrusion Drawdown Ratio Calculator
Compare annular die-exit area with finished tube area for a documented tube or pipe tooling setup.
Formula and method
Area drawdown ratio = (die OD² − tip OD²) ÷ (product OD² − product ID²).
Inputs and units
Measure the die inside opening as die OD, the tip outside diameter, and the final conditioned product OD and ID. Use one length unit for all four diameters.
Worked example
A 12 mm die opening with an 8 mm tip producing 8 mm OD × 6 mm ID tube gives an area drawdown ratio of 2.86:1.
When to use it
Use when recording an existing tube setup, comparing a planned product/tooling combination, or communicating the geometric basis of a trial.
How to interpret the result
Compare the result only with material- and process-specific tooling guidance. The calculator deliberately supplies no universal acceptable range.
Assumptions and limitations
The geometric ratio does not predict die swell, melt strength, draw resonance, wall eccentricity, sizing behavior, vacuum response, orientation, or final tolerance capability.
Validation guidance
Measure actual die and tip land geometry and conditioned tube dimensions. Confirm wall distribution around the circumference and validate the setup in a controlled trial.
FAQ
Can this calculator select the die and tip?
No. It documents one area relationship. Resin-specific extrusion guides, tooling experience, swell, draw balance, sizing, and trial results govern selection.
Sources
DuPont Surlyn Extrusion Guide · Eastman: Extrusion of Tubing and Profiles