Abstract: A method of producing a blown film with a controlled thickness profile, comprises the steps of: extruding molten plastic through an annular extrusion die; cooling the molten plastic using an annular blower around the extrusion die, positioning one or more sources of supplemental air at one or more desired circumferential positions about the annular extrusion die and adjacent to the extruded molten plastic, the annular blower and the one or more sources of supplemental air being operated to supply cooling air to the molten plastic between the annular extrusion die and the frost line where the molten plastic solidifies; and controlling the one or more sources of supplemental air to form one or more areas of increased thickness along a circumferential thickness profile of the blown film, the one or more areas of increased thickness having a thickness that is greater than an average thickness of the circumferential profile.

Abstract: A method of producing a blown film with a controlled thickness profile, comprises the steps of: extruding molten plastic through an annular extrusion die; cooling the molten plastic using an annular blower around the extrusion die, positioning one or more sources of supplemental air at one or more desired circumferential positions about the annular extrusion die and adjacent to the extruded molten plastic, the annular blower and the one or more sources of supplemental air being operated to supply cooling air to the molten plastic between the annular extrusion die and the frost line where the molten plastic solidifies; and controlling the one or more sources of supplemental air to form one or more areas of increased thickness along a circumferential thickness profile of the blown film, the one or more areas of increased thickness having a thickness that is greater than an average thickness of the circumferential profile.