| 摘要 |
PURPOSE:To obtain a sprue for a injection molding die having a smooth tapered hole eliminating drilling with a drill and grinding of a tapered hole as in the past by forming a sprue body on a tapered mandrel by electroforming. CONSTITUTION:A cylindrical brass material is formed on a madrel 11 having a thinly tapered part 13 by machining it leaving the base thereof and then, the surface of the tapered part 13 is mirror finished by a sandpaper or the like. An electroformed layer 14 of a nickel-cobalt alloy is formed on the circumference of the tapered part 13 by a sidely accepted electroforming with the mandrel 11 as electrode and after the outer periphery of the electroformed layer 14 is cut to the desired diameter, the mandrel 1 is withdrawn to obtain a sprue body 15. After retaining holes 17 and 17 are drilled on the outer wall of at the tip of the sprue body, the sprue body is forced into a flanged outer cylinder 18 and pins 20 and 20 are inserted into the retaining holes 17 and 17 and pin holes 19 and 19 of the outer cylinder 18 to obtain a desired sprue. |
