Screw-type mixers, or extruders, of which there are numerous design configurations, are widely employed for the extrusion of molten or plasticized polymers to semifinal- and final-product forms. These machines are also used for preparing additives such as resins for plastification, pigments, and others. Components to be mixed are normally doped with additives in a feed tunnel to the machine, thus providing a relatively homogeneous mass which is then extruded in the main working chamber (screw channel). Mixing and material extrusion can be accomplished in single or double rotating screw machines.