Coat-Hanger Extrusion Die Calculator
Sheet & cast film extrusion: Calculate coat-hanger distribution manifold pressure loss, slit gap shear rate, power-law flow uniformity, and die lip gap pressure drop.
Die Geometry & Throughput
Die Pressure Loss & Shear Distribution
Recommended Tools & Equipment
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Frequently Asked Questions
How does a coat-hanger die achieve uniform sheet thickness across its width?
In a flat extrusion die, polymer melt enters at a single central port and must travel varying path lengths to reach the edges versus the center. A coat-hanger geometry tapers both the manifold radius and the island feed angle so that the combined pressure drop along the manifold and through the die lips is perfectly identical at every point across the width.
Why does pseudoplastic shear-thinning (index n) matter in die design?
Polymer melts are strongly pseudoplastic (n ≈ 0.3 to 0.45). At higher shear rates, viscosity drops steeply. If an extrusion die designed for n = 0.5 is run with an n = 0.25 polymer, the edges will receive significantly different flow rates than the center, creating severe "dog-bone" or hourglass gauge variation.
What is die lip bowing and how does lip pressure affect gauge uniformity?
Internal melt pressures of 50 to 100 bar exert thousands of kilograms of hydraulic force pushing the upper and lower die lips apart. Because the die body is clamped at its ends, the center flexes open wider (bowing), causing extruded sheets to be thicker in the center than at the edges unless compensated with thermal adjustment bolts.