Solids Transport in Single-Screw Extruders.

Classical solids transport theory for single screw extruders does not give adequate predictions for pressure generation. This is partly due to shortcomings of the theory but is also caused by incorrect interpretation of the theory and by inadequate experimental methods. The pressue build-up in a direction perpendicular to the screw flight is taken into account in a two dimensional transport theory. A suitable method of measuring pressure-rise is described. The effect of axial grooves in the entry section of the cylinder is analyzed and the concept of stiffness of the pressure build-up zone is discussed. Pressure independent mass flow may be obtained by maintaining a zone of Archimedean transport in the first part of the machine.