Blown film extrusion

Blown film extrusion is the most common process for the production of continuous films that are used primarily for packaging. The first step in the process is to melt the plastic in the extruder, the molten polymer then enters an annular die head and is formed into a tube of plastic material. For multilayer films one extruder per material is required, their melt strands are combined in the die head to produce a tube of plastic with concentric layers.

After exiting the die the film tube, which is still in a plastic state, is pulled upwards by nip rollers. At the same time compressed air is blown into the film tube to achieve the desired film thickness and width. Chilled air is blown on the outside of the tube. Once cooled the film approaches the nip rollers and the bubble of film is gradually flattened into ‘lay-flat’ tubing. The nip rolls transport the film to the in-line slitters and roll winders at the base of the line.