Extrusion-forming device and method for manufacturing formed article by use of this device

An extrusion-forming device comprising:

• an extruding portion having a drum including a supply port through which a clay containing a ceramic forming material flows into the inside, a screw having a rotary shaft and a spiral rotary blade disposed along the rotary shaft and configured to convey the clay in an extruding direction parallel to the rotary shaft while kneading the clay by the rotation of the rotary blade, and an extrusion port through which the clay is discharged;
• and
• a forming portion including a die through which the clay is extruded and which has forming grooves arranged in a forming face, and arranged along the extruding direction of the extruding portion,
• wherein the screw includes, as the screw on the side of the supply port, at least two supply port side screws having supply port side rotary blades provided so as to be rotationally symmetric with respect to the rotary shaft and, as the screw on the side of the extrusion port, at least one extrusion port side screw having an extrusion port side rotary blade, and
• a ratio P/D is in a range of 0.5 to 0.9, in which D is the diameter of the outermost periphery of the rotary blade, and P is the pitch of the extrusion port side rotary blade along the extruding direction.