| 摘要 |
PURPOSE:To obtain a molding which is of high-precision and stable, by a method wherein the titled resin is cast evenly by providing a runner for skin layer resin between an injection cylinder unit for the skin layer resin and the starting point of the runner and providing further a gate, whose resin circulation cross section has been narrowed, on the runner. CONSTITUTION:A runner plate 8 is provided with a first runner 8a joining a first and second sprues 6a, 6b with each other. A resin sink 8d provided on the runner plate is provided on a straight line connecting between a first gate 8b, whose cross-sectional area is narrower than that of a runner for skin layer resin, and the sprue 6b for core layer resin. A second runner 8a2 communicating with the resin sink 8d and extending evenly and radially on the surface which is flush with Y1-Y'1 surface is provided. As the first gate is provided on a joint between the first runner and second sprue like this, when second resin is cast through the second sprue after injection of first resin, a back flow of the second resin to a first runner side stops at the inside of the first gate. Then it follows that the second resin is distributed and cast to each of the second runners by even quantity and that even resin pressure influencing excessively upon accuracy of a molding is applied evenly to the runner.
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