Integrated single and twin screw extruder

An extruder comprising:

• a first barrel assembly;
• a second barrel assembly detachably coupled to the first barrel assembly;
• a die mountable to the first barrel assembly with the extruder in a single screw configuration and to the second barrel assembly with the extruder in an integrated single and twin screw configuration;
• a first screw having a first threaded portion and a second threaded portion, the first threaded portion being housed within the first barrel assembly and configured to provide upstream material processing in the integrated single and twin screw configuration, and the second threaded portion being housed within the second barrel assembly and configured to provide downstream material processing in the integrated single and twin configuration;
• and
• a second screw having a non-threaded shaft portion and a threaded portion, the threaded portion of the second screw being housed within the second barrel assembly and configured to provide the downstream material processing with the second threaded portion of the first screw, and the non-threaded shaft portion being housed within the first barrel assembly and lacking threads circumferentially about the second screw along the length of the first barrel assembly so as to provide screw threads in the first barrel assembly only by the first threaded portion of the first screw.