2. Flat dies

The molten polymer flows through a flat die with a rectangular end section. One of the aims of this tool is to achieve the best possible temperature and thickness uniformity across the die (i.e. perpendicular to the direction of flow). The air gap (i.e. the rectangular cross-section through which the molten polymer flows) of the dies used in cast film can be adjusted either manually or automatically. Uniformity of flow distribution is linked to the design of the channel (commonly called a manifold), and a flexible lip is used for final adjustment of the melt thickness. In some applications, a throttle bar is used to adjust flow regularity.