Extrusion

is a process in which individual components of a film, often present as granulate, are melted and homogenized in an extruder. The extruder consists of a heated spiral conveyor that is built in a cylinder. The granulate is filled in via a funnel on one side of the cylinder, from where it is transported through the cylinder by the rotating spiral. The granulate then melts due to the heating elements on the cylinder and the friction. While the melting granulate is transported, the geometry of the auger narrows which builds up pressure. After the compression zone, the granulate is fully molten and can be fully homogenized with additional mixing elements at the auger. The liquid polymer is now pressed through a filter whereby gels and degraded or non-melted material is separated. Afterwards, the polymer is compression or injection molded ¹ and proceeded to further molding steps.