Extrusion Shaping
A constant-thickness die generally ensures good equilibrium of the forces in play during the extrusion process. The lower the body moisture content the higher the plastic body attrition forces; it is thus easily understandable that, whatever the other parameters of the extrusion process described above, that the water contained in the ceramic mass must provide the body with enough cohesion to equilibrate the attrition forces with the extrusion walls and the extrusion mouth.
During extrusion-shaping density is a direct function of the water content of the ceramic mass: more specifically, the density of the extruded product increases as the water content in the mass decreases. If the goal is to obtain semi-finished products with as high an apparent density as possible, then it will be necessary to reduce the water content that goes into the mix being extruded. The attrition forces in play vary from machine to machine, so laboratory analysis does not always provide results valid at industrial level.
To be Contd…
