In an injection molding method, using a heating cylinder having on the front end thereof a discharge nozzle, a single axis screw is rotatable inside the heating cylinder, a fiber-supplying device fills reinforcing fiber into the heating cylinder, and injection molding is performed while supplying the reinforcing fiber and the resin starting material separately and supplying the reinforcing fiber on the front side of the resin starting material. The method includes a plasticization process for obtaining a specified amount of a kneaded product by retracting the screw while rotating in the normal direction to melt the resin starting material and knead reinforcing fiber into the melted resin starting material, and an injection process for discharging the kneaded product from the discharge nozzle by advancing the screw. Reinforcing fiber is supplied into the heating cylinder in the injection process.

In order to be capable of reliably supplying a prescribed amount of fiber materials into a heating cylinder for each cycle and continuously manufacturing a homogeneous composite material, a plasticizing unit is provided with a fiber supply device 3 that supplies prescribed amount of fiber materials A2 having a prescribed length into the heating cylinder 1. The fiber supply device 3 is provided with: a cutting section 12 that cuts off a long fiber material A1 pulled out from a reel 11 into a prescribed length; a pressure-feeding section 13 that presses the fiber materials A2 having the prescribed length cut off by the cutting section 12 into the heating cylinder 1; and a fiber transfer device 45 that forcibly transfers the fiber materials A2 accumulated in the cutting section 12 to the pressure-feeding section 13. The pressure-feeding section 13 is constituted by a press cylinder 41 and a press piston 42, and the fiber transfer device 45 is constituted by a vacuum device.

In order to be capable of reliably supplying a prescribed amount of fiber materials into a heating cylinder for each cycle and continuously manufacturing a homogeneous composite material, a plasticizing unit is provided with a fiber supply device 3 that supplies prescribed amount of fiber materials A2 having a prescribed length into the heating cylinder 1. The fiber supply device 3 is provided with: a cutting section 12 that cuts off a long fiber material A1 pulled out from a reel 11 into a prescribed length; a pressure-feeding section 13 that presses the fiber materials A2 having the prescribed length cut off by the cutting section 12 into the heating cylinder 1; and a fiber transfer device 45 that forcibly transfers the fiber materials A2 accumulated in the cutting section 12 to the pressure-feeding section 13. The pressure-feeding section 13 is constituted by a press cylinder 41 and a press piston 42, and the fiber transfer device 45 is constituted by a vacuum device.

The injection molding apparatus of the present invention includes: a heating cylinder; a screw that is provided rotatably in an inner portion of the heating cylinder; a resin feed hopper that feeds a resin pellet; and a fiber feed device that is provided ahead of the resin feed hopper and feeds reinforcing fibers into the heating cylinder. The screw includes a first stage that is located on a rear side, and in which the resin pellet is melted, and a second stage that is located on a front side, and in which the melted resin pellet and the reinforcing fibers are mixed, and a lead of a second flight provided in the second stage is larger than a lead of a first flight provided in the first stage.

A mixer (1) for mixing a mixing material (13) in polymer processing comprises a mixing chamber (2) and more than two rotors (6a-6d) arranged in the mixing chamber (2). In particular, the rotors (6a-6d) can be configured to interlock.