| 摘要 |
PURPOSE:To obtain a cylinder having plural protruded undercut parts by a simple metal mold, by a method wherein a cylindrical cavity is contoured by an outer mold, a first core pin and a second core pin slid therewith and, after a hard resin is injected thereinto and solidified therein, each molding element is withdrawn. CONSTITUTION:After a molten hard resin is injected into a cavity 9 to be molded into a cylinder 1 after solidification, a second core pin 5 and an outer mold 7 are withdrawn and a first core pin 4 is subsequently withdrawn. Because three internal spaces 10 are formed by preliminary withdrawing the second core pin 5, the cylinder 1 can be deformed into an almost triangular shape when the first core pin 4 is withdrawn and, even in the hard resin, the deformation amount of a part containing a protrusion 2 is made large and the first core pin 4 can be easily withdrawn. |
