| 摘要 |
PURPOSE:To obtain the gate bush for a mold having high dimensional accuracy and high smoothness, by forming a gate bush main body comprising an electroforming layer to the tape part of a mandrel and demolding said gate bush main body from the mandrel to form a taper hole having a smooth inner peripheral surface to the gate bush main body. CONSTITUTION:A bottomed cylindrical electroforming layer 14 comprising a nickel/cobalt alloy is formed to the outer periphery of a taper part 13 by an electroforming method. A base part 12 is chucked while a mandrel 11 is inserted in said electroforming layer 14 and the electroforming layer 14 is cut to form a gate bush main body 15 having a predetermined outer diameter. Next, when the mandrel 11 is drawn out from the gate bush main body 15, a taper hole 16 is formed. This gate bush main body 15 is inserted in a preformed flanged outer cylinder 18 under pressure. After the gate bush main body 15 is inserted in the flanged outer cylinder 18 under pressure, pins 20, 20 are inserted in the pin holes to prevent the drawing-out of the gate main body 15. At last, a nozzle hole 21 with a fine diameter is provided to the bottom part of the electroforming layer 14 by drilling. |
