Abstract: An injection molding apparatus includes an injection unit; a clamping unit; a mold assembly including a mold plate, a manifold, an actuator mounted on and upstream of the manifold, and at least one nozzle coupled to and downstream of the manifold, the actuator for reciprocating a valve pin between an open position allowing a melt to pass through the nozzle and a closed position preventing the melt from passing through the nozzle, the mold assembly further including a biasing mechanism biasing the actuator upstream towards the mold plate.