A non-plug solid conveying theory for plasticating extrusion is proposed in this paper. The polymer granules are treated as bulk pellets which move down the screw channel at different speeds, rather than as a plus which never experiences deformation during extrusion. The pellets system is considered as a linear elastic system, and can only resist compressive forces but not tensile forces. Based on elastic mechanics and virtual work principles, a mathematical model for non-plug solid conveying is proposed. Finite element method (FEM) is used to determine the relationships between internal stress and velocity profiles of the pellets in the screw channel, the internal stress states at any point in the screw channel, etc. The prediction also proved the existence of the optimum depth of the screw channel and the optimum helix angle of the screw. Most of the experiments have been carried out on an extruder with glass windows in its barrel. The experiments confirm the validity of the theory.
