Control of the Cross Section Geometry of Extruded Dental Porcelain Slurries for Rapid Prototyping Applications

This study investigates the dependence of the cross section geometry of extruded dental porcelain slurries on the rheological property of the slurry and the extrusion conditions. It is found that a pseudoplastic slurry is a basic requirement for obtaining extruded lines with rectangular cross sections. The cross section geometry of the extrudate is also strongly affected by extrusion parameters including the extrusion nozzle height, nozzle moving speed, and extrusion rate. Proper combinations of these extrusion parameters are necessary in order to obtain extrudates with near rectangular cross sections. The results obtained have been explained in terms of the interactions among the rheological properties of the slurry, the shear rate imposed on the slurry during extrusion, the wettability of the slurry on the substrate, and the forced flow of the slurry during extrusion.