| 摘要 |
PURPOSE:To eliminate an undercut part of a molded screw even if a screw pitch is large by a method wherein a plastic screw mold is composed of three or more split molds dividing a screw molding cavity of the mold into three or more parts around a screw shaft. CONSTITUTION:A mold 10 is composed of four split molds 12A-12D dividing a screw molding cavity 11 into four parts around a screw shaft. In this manner, even if a pitch P of a plastic screw 1 is large and an angle theta of skew of thread is excessively large, a buffer area does not exist between the threads of the molded screw 1 and the split molds 12A-12D. As a result, an undercut part of the molded screw 1 is eliminated. Therefore, when the screw 1 is removed from the mold, an occurrence of a mar, a burr, and the like can be prevented. |
