| 摘要 |
<p>The method of molding a cylindrical portion of a cylindrical material of a sheet metal according to the present invention comprises a method of pressing a cylindrical portion of a cylindrical material, which is fitted around a rotary mold, against the rotary mold by a molding roller while turning the cylindrical material with the rotary mold. According to the present invention, the part of the cylindrical portion which is pressed by the molding roller is shifted in a stepped manner from an open end of the cylindrical portion toward a root region thereof. For example, when the parts to be pressed by the molding roller of the cylindrical portion are divided into a first part to be pressed on the open end side thereof and a second part to be pressed on the root side thereof, the first part is pressed first by the molding roller so as to be thinned and stretched, and the second part is then pressed by the molding roller so as to be thinned and stretched. Owing to this method, the molded cylindrical portion does not open in the shape of a trumpet.</p> |
