A rotor core manufacturing method and system allow for molding permanent magnets in an unmolded rotor core to provide an electric motor molded rotor core. The unmolded rotor core includes a shaft and rotor core body having a central through-hole along a longitudinal axis, magnet cavities around the axis with magnets therein. The shaft lies in the central through-hole and projects therefrom, and the molded rotor core includes the rotor core body having the magnets fixed in the cavities. The method includes inserting an unmolded rotor core between the first and second molds of a rotor core molding system; moving the molds together to clamp the rotor core body of the unmolded rotor core with a predetermined pressure; providing a molding material into the magnet cavities; letting the molding material cure within the magnet cavities to a molded rotor core; opening the molds and removing the molded rotor core.

A resin molding device includes: a lower mold on which a substrate is placed; an upper mold in which a cavity is formed by a side block and a cavity block provided so as to be capable of ascending and descending vertically with respect to the side block; a clamp mechanism which clamps the lower mold and the upper mold; a transfer mechanism which supplies a resin material to the cavity by a plunger; and a controller which performs first final adjustment control for adjusting a clamp load of the clamp mechanism to a final clamp load after the cavity has been filled with the resin material supplied from the transfer mechanism and which performs second final adjustment control for driving the plunger after the first adjustment control has been completed and thereby adjusting a plunger load applied to the plunger to a final plunger load.