Abstract: A plastic mold injection apparatus (300) is provided. The apparatus includes a runner system (110) that delivers a plastic melt through a flow tube (111), a cavity (120) that receives the plastic melt, and a hydraulic drive mechanism (130) that drives a pin in and out of a flow tube of the runner system. The runner system, the cavity, and the hydraulic drive mechanism are internal to, and operate within, the apparatus, to mix the plastic melt in the cavity. The hydraulic drive mechanism moves a first pin (141) out-of-phase with a second pin (142) to mix the plastic melt in the cavity. A first hydraulic pipe (151) removes hydraulic fluid to pull plastic melt into a first flow tube (111) from the cavity. A second hydraulic pipe (152) delivers hydraulic fluid to push out plastic melt from a second flow tube (112) to the cavity.