subject: Twin And Single Screw Extruder [print this page] In a twin screw extruder including a barrel, which has two screws disposed in parallel in its inside and an opening at one edge, and an extrusion molding die disposed to the opening side of the barrel through a straightening vane and a filter net, the straightening vane includes a first straightening vane and a second straightening vane, the first one has a hole forming region having plural through holes formed in a region whose size and shape are in agreement with the size and the shape of the inner periphery of the opening portion, and the second one has a hole structure whose size and shape of its inner periphery at one opening edge are in agreement with the size and the shape of the hole forming region, and its sectional area is reduced once in a process to the other opening edge and then expanded in a taper shape.
A structure of a conventional twin screw extruder can be basically employed as it is as the structure of twin- screw extruder of the present invention except the straightening vanes described above. In the single screw extruder of the present invention, the two screws in the barrel may be rotated any of the same direction and a different direction.
Although the shape of the formed body formed by the single screw extruder of the present invention is not particularly limited a long as it is a shape obtained by extrusion molding, the twin- screw extruder is preferable to form, for example, a honeycomb formed body which is liable to be deformed because it employ thin partitions to partition cells.
As shown in Table 1, in the comparative example using the conventional single screw extruder, the roundnesses of the honeycomb formed bodies are greatly changed at the edge faces thereof due to the change of the amounts of extrusion as well as the roundnesses have large differences between one edge faces and the other edge faces, and further the roundnesses have large values. In contrast, in the example using the twin- screw extruder of the present invention, even if the amounts of extrusion change, the roundnesses of the edge faces of the honeycomb formed bodies are not so greatly changed, and the differences between the roundnesses of the one edge faces and the other faces and the values of the roundnesses are small as compared with those of the comparative example.
