How does extrusion at OPI Plastics work?

At Oosterwolde Plastic Industry we produce flexible film packaging. The film is blown at our extrusion department. Polyethylene granulates are poured into a cylinder through a funnel, and heated. Within that cylinder, the melted mixture is forced through an orifice by a rotating propeller, after which the film is blown outwards, in the shape of a balloon. After it has cooled down, the rollers flatten the film to a double layer, and the film is rolled up. Now the film is ready for further processing.