| 摘要 |
PURPOSE:To realize a highly accurate molded item by a method wherein a cylindrical cavity having an inner surface, which limits the outer peripheral surface of a cylindrical molded item with multiple screws, is constituted by assembling outer peripheral blocks, which are produced by dividing the screws with the same number of parting faces as that of screw flight consisting of spiral surface perpendicular to the center axis of the cylindrical cavity and having the same lead angle as that of the screw, by the parting face. CONSTITUTION:A cavity 30 having a cylindrical outer peripheral surface is equipped with a hollow part 31, the inner surface of which limits the outer peripheral surface of the synthetic resin layer 3 of a female screw rotor 1. A line segment A-B perpendicular to the center axis O is obtained by a line, which extends radially from the center axis O of the cavity 30 through the apex of a screw 4. A spiral surface 32 having the same lead angle as that of the screw is obtained by integrating said line segment A-B in the direction of the center axis O. By dividing the cavity 30 by these six spiral surfaces 32, six outer peripheral blocks 33, each of which is pinched between adjacent spiral surfaces 32, are produced. These six outer peripheral blocks 33 are finished one by one by machining, grinding and the like and assembled together by the parting faces in order to form the cavity 30. |
