The cast extrusion process is a continuous operation of melting and conveying a polymer in a heated screw-and-barrel assembly (an extruder). The homogenous melt is forced to flow through a flat sheet die from which it exits at the desired width and thickness. The molten sheet is wound through the nips of a three-chill-roll stack for thickness sizing and cooling. The solid sheet is then cooled further on a cooling conveyor while the edges are trimmed to final desired sheet width. The sheet is either rolled or sheared into sections for later use.