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Coat Hanger Die
Meaning
Polymer extrusion hardware distributes molten plastic uniformly across a wide slit to produce sheets or films. A coat hanger die utilizes a contoured internal manifold that tapers from the center to the edges to balance flow resistance. This geometry ensures that the plastic exits the exit lips at a constant velocity and thickness, but it does not apply to round profile extrusion.
Manifold Geometry
Flow channel design compensates for the pressure drop that occurs as the polymer melt travels toward the outer margins. The coat hanger die features a curved, branching shape that mimics the sloping shoulders of a garment hanger. This specific curvature is calculated based on the rheological behavior of the plastic to achieve a balanced flow rate across the entire width.
Production Impact
Uniform thickness prevents the formation of structural weak points or optical distortions in the finished plastic film. Inconsistent flow leads to gauge variation, which causes winding problems and uneven cooling on the chill rolls. Maintaining a precise flow distribution across the width improves the overall yield of the production run.
Capital Cost
High precision manufacturing is required to machine the internal surfaces of these flow distribution systems. Purchasing a coat hanger die involves a substantial financial commitment and requires extensive testing to match the polymer grade. Operating the system under incorrect temperature profiles risks permanent degradation of the internal chrome plating.