| 摘要 |
PROBLEM TO BE SOLVED: To prevent a sink mark of a crystal resin by slightly opening a die after the die is opened and a molten resin is first injected, the die is clamped and shaped while molten resin is then injected in a die cavity and shaped, providing a gap between the molding and the cavity, and clamping the die while surface resin is capable of being flowed after a given time. SOLUTION: A polypropylene resin of a molten state in a die cavity clamped by a mold clamping unit 300 and in an injection unit 200 is metered by a first injection timer 533. At the time of elapsing a given time after completion of filling, a movable die 404 is retracted so that a gap between the molding surface and the cavity surface becomes a given value. A pressure holding state is maintained for a given time after the first injection, and then a second injection is executed. At the time of elapsing given time, the mold 404 is advanced, the die is again clamped, a thick part generated by the secondary injection is corrected, shaped, and held for a given time. Then after a given time is elapsed, a gap is provided as a heat insulation layer between the surface of the molding and the surface of the cavity, held for a given time, the die is clamped and then opened. Thus, a sink mark can be prevented at the thick part of a crystalline resin.
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