| 摘要 |
PURPOSE:To stably obtain a product of prescribed form, by closing the nozzle of an injection cylinder for a prescribed time after the pressure in a mold has become a predetermined value, and then opening the nozzle again to maintain the pressure. CONSTITUTION:A nozzle 2 at the front end of an injection cylinder 1 is fitted with a needle valve 3 to adjust an injection passage for a molten resin. The passage is controlled by an in-mold resin pressure detector 8, a controller 10, a cylinder 6, a link 5, etc. The needle valve 3 is opened to inject the resin into a metal mold 9. When the pressure of the resin in the mold has reached a set maximum value Pmax, the needle valve 3 is closed according to an instruction from the controller 10. After a prescribed time thetas has elapsed in that state or when the pressure of the resin in the mold has reached a prescribed value Ps, the needle valve 3 is opened again to inject an additional quantity of such a resin to compensate the contraction of the former injected resin due to cooling. The pressure of the resin in the mold is thus maintained. After the injection, the needle valve 3 is closed. Plasticization is then effected. |
