4. Drawing stage

4.1 Thermostated roller

The dimensions of the thermostatically controlled roll must be determined in relation to the overall throughput of the production line, to ensure even film cooling. Design parameters depend on the extruded polymer, film dimensions and machine speed range. The extruded film is cooled on the thermostatically controlled roll, which can have a diameter of between 400 and 1,200 mm, depending on the line size. The internal structure of the roll is designed to achieve the required cooling capacity with maximum thermal stability. The surface finish of the roll (which is chosen to a certain extent according to the nature of the polymer being processed) is generally highly polished (roughnesses of less than 0.3 µm are typical), but for high line speeds, surface matting...