Extrusion Shaping
The relationship between the extrusion pressure needed to extrude a certain material with a certain extrusion mouth as a function of the extrusion rate is dependent on the minimum pressure characteristics of the body and the characteristics of the extrusion mouth. Variations in pressure caused by changes in the extrusion rate are somewhat limited, and depend on the plasticity of the body. If the water content in the body is increased the minimum pressure drops.
Thus to obtain higher extrusion rates at lower extruder pressures the water content in the body has to be increased; However, if pressure is too low it becomes difficult to prevent the piece from deforming under its own weight after extrusion. This therefore constitutes a maximum limit to water content in the body. If, instead, we use bodies with below-standard water content piece consistency will be greater yet it will be necessary to operate at higher extrusion pressures.
To be Contd…
