The book teaches the fundamentals of single-screw extrusion such that fast troubleshooting and process optimization and design are possible. The fundamental processes that are occurring in the machine are developed from the natural reference point of a rotating screw rather the traditional rotating barrel. These fundamentals are then combined with the chemistry of polymers and the physical properties related to processing to troubleshoot and optimize extrusion processes. Many industrial extrusion problem case studies are presented. In each case study, the root cause of the problem is identified along with the solution. A fundamental view of the processes that occur in a single-screw machine from the natural reference frame; i.e., screw rotation. The theory is discussed and compared to experimental data and to a rotating barrel reference frame. Topics include: polymerization chemistry and degradation mechanisms for polymers, physical properties related to processing (e.g., rheology, heat capacity, dynamic friction, bulk density and pellet compaction, melt density), and 30+ case studies for troubleshooting extrusion problems. A detailed description of the problem and the solution is presented so the reader can implement the solution on their own equipment.