A controller for an injection molding system is in communication with a melt flow control unit, a gas assist control unit, and a gas counter pressure control unit. The controller can effect real-time adjustments to gas assist pressure and/or gas counter pressure as a function of melt pressure or flow front position.

[Problems] The objective of present invention is to provide the mold, injection molding system and method capable of limiting the outflow of pressurized fluid injected into a mold cavity.

[Solution] A mold device and a molding device comprising: a shaft body 27 provided at least on one mold among a first mold 205 and a second mold 206 that form a molding space 200, the shaft body being used for pushing out a molded article formed from a resin injected into the molding space 200; a ring-shaped elastic member for supporting the shaft body 27 in which an opening formed along the circumferential direction is oriented toward the said molding space; and an injection portion provided on at least one mold among the first mold 205 and the second mold 206, the injection portion being used for injecting a pressurized fluid into the molding space 200.