A flex plate for a guiding device of an injection molding machine includes a body extending between a front surface, a back surface, a top surface, and a bottom surface. A plurality of through holes extend between the top surface and the bottom surface for aligning the flex plate with a foot of the guiding device, and a plurality of guide shoe holes formed in the bottom surface of the flex plate couple the flex plate to a guide shoe of the guiding device. A front plate couples the front surface of the flex plate to the foot of the guiding device, and a plurality of slots define a central portion of the flex plate. The central portion of the flex plate is elastically deformable about a torsional axis and can pivot relative to the guide shoe and foot of the guiding device.

A partial reflux injection function part 5 is provided according to which resin R at the front side of a screw head portion 4s is injected into the metal mold 2 to fill the metal mold 2 with the resin R in synchronization with the refluxing of a predetermined amount of the reflux resin Rm to be used as a part of the resin R to the screw body part 4m side at the rear side of the screw head portion 4s through the inner side of the screw head portion 4s and/or the outer periphery side of the screw head portion 4s. A control function is provided that sequentially performs a plasticization step Wi1 to rotate the screw 4 in the heating cylinder 3 to thereby subject the resin in the heating cylinder 3 to a plasticization processing; an injection step Wi2 to allow, after the completion of the plasticization step Wi1, the screw 4 to move forward to thereby inject, into the metal mold 2, a part of the plasticized resin R accumulated at the front side of the screw head portion 4s of the screw 4 to fill the metal mold 2 with the resin; and a plasticization promotion step Wi3 to allow, after the completion of the injection step Wi2, a part of the remaining part of the accumulated plasticized resin R to be refluxed as the reflux resin Rm to the rear side of the screw head portion 4s.