Extruder Screw Design

The single most important mechanical element of a screw extruder is the screw. The proper design of the geometry of the extruder screw is of crucial importance to the proper functioning of the extruder. If material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. Screw design is often still considered to be more of an art than a science. As a result, misconceptions about certain aspects of screw design still abound today. Since the theory of single screw extrusion is now well-developed (see Chapter 7), the design of screws for single screw extruders can be based on solid engineering principles. Thus, screw design for single screw extruders should no longer be an art, but a science based firmly on the principles of polymer processing engineering.