Mold device for resin molded article, molding apparatus, molding system, and method for manufacturing molded article

A method for manufacturing a foam-molded article by performing a gas counter pressure (GCP) using a sealed mold, a mold clamping mechanism, a shaft body for ejecting the foam-molded article from the sealed mold, and at least one of:

• a loaded O-ring for sealing the shaft body;
• an O-ring having a U-shaped groove for sealing the shaft body;
• and a spacer block for sealing the shaft body, the method comprising:
• a step of compressing a sealed space including a molding space inside the sealed mold by injecting a gas having a pressure of 0.6 MPa or more into the sealed space, the gas being selected from the group consisting of air, nitrogen gas, carbon dioxide, and a mixed gas of two or more thereof;
• a step of filling a foamable resin into the molding space by 90 volume % or more in a state that the sealed space is compressed by the gas;
• a step of discharging an amount of the gas injected into the sealed space to atmosphere by opening a discharge valve after the foamable resin is filled into the molding space by 90 volume % or more, wherein the step of discharging the gas is performed through a fixed side or a mobile side of the sealed mold, the fixed and mobile sides of the sealed mold defining the molding space;
• a step of retreating a mobile side of the mold clamping mechanism by 0.1 mm to 2 mm at the same time as when the step of discharging the gas is started, during the step of discharging the gas, immediately after the step of discharging the gas, or when a specified delay time has elapsed after the step of discharging the gas is finished for performing at least one of a mold-back and a core-back so as to discharge an amount of the gas injected into the sealed space from a parting where the fixed side and the mobile side of the sealed mold are mated with each other and increase a foaming ratio of the foamable resin in a state that a cooling and a solidification of an inside of the foamable resin are not finished;
• a step of cooling and solidifying the foamable resin, thereby forming the foam-molded article;
• and
• a step of opening the sealed mold and taking the foam-molded article from the sealed mold.