Extrusion begins with raw materials, typically in the form of pellets or granules, which are loaded into a hopper. As the materials move into the extruder, they encounter a rotating screw that helps to mix, heat, and push the material forward. The heat generated through friction, combined with the external heating from the barrel, causes the thermoplastic to melt. Once the material is sufficiently melted and homogenized, it is forced through a die that shapes it into the desired profile.