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Air entrainment during film winding with layon rolls

Forrest, A. W., Jr.
Excessive air entrainment has long been recognized as a cause for telescoping and other forms of wound roll defects. To eliminate a portion of the air, exclusion devices such as layon rolls are often used. Air entrainment calculations in the literature generally do not consider this geometry. When layon rolls are employed, the high pressures under the nip make consideration of the surface roughness necessary. Here, the contact pressure is supported by a combination of the surface roughness and the entrained air pressure. After the nip passes, the entrained air expands and a final winding condition is achieved. This paper describes an analytical procedure that calculates the amount of entrained air considering these effects.