The mixture of polymers (polyethylene, polypropylene, polyamides and other resins) in the form of variously colored granules, along with additives and strengtheners, is put into the extruder.

This is where fusion takes place by the heat produced by a cylinder equipped with resistors and by the action of the screw inside the cylinder itself, which pushes the material towards the extruder making it come out in the form of flat ( Cast ) or annular ( Blown ) lamina, properly pressed and blown, is then transformed into the desired film.

Typical semi-manufactured types such as flat films, flat tubular films or accordion-shaped films suitable for packaging. 

technology deriving directly from extrusion is coextrusion, which combines the action of a variable number of mass-produced extruders which – with different materials- contribute to the production of one final semi–manufactured item.  

This procedure produces radial coextruders, which have different materials in the extrusion (coextrusions that at times are alternately rigid/elastic or transparent/opaque) or axial coextrusions, which have materials that differ from the section.