A method of making a support arm includes heating a mold to a glass transition temperature of a thermoplastic material; injecting the thermoplastic material comprising a filler into the mold and allowing the thermoplastic material to conform to the mold; cooling the mold to an ejection temperature to form the support arm; and ejecting the support arm from the mold; wherein a cross-section of the support arm taken along a line from an inner edge to an outer edge of the support arm comprises a first U shaped portion and a second U shaped portion.

A molding die includes: a pair of dies, i.e., a first die and a second die respectively having abutting surfaces; a first die part and a second die part respectively having cavity forming portions inside which a cavity is formed, and thick portions provided at both ends of the cavity forming portions, the die parts being detachably fitted to die part attachment grooves provided in the abutting surfaces of the pair of dies; and induction heating coils for heating a surface of the cavity, wherein thicknesses of the cavity forming portions are smaller than thicknesses of the thick portions, and the distance between the induction heating coils and the cavity is smaller than the thicknesses of the thick portions.

A method for manufacturing a rotor includes clamping a first die and a second die so as to hold a core between the first die and the second die in a state in which a magnet is accommodated in a magnet housing hole of the core, injecting thermoplastic into the magnet housing hole, and opening the first die and the second die and removing the core and the magnet from a space between the first die and the second die. The removing the core and the magnet includes removing the core and the magnet from the space between the first die and the second die when a temperature of the thermoplastic injected into the magnet housing hole is higher than or equal to a glass transition point and lower than a melting point.

An injection molding device according to an embodiment of the present disclosure includes a first mold including a first injection port through which a raw material is injected; a second mold including a heating member; a first movable mold facing the first mold or the second mold and having a first cavity formed therein; and a second movable mold facing the first mold or the second mold and having a second cavity formed therein, wherein the position of the first movable mold and the position of the second movable mold can be changed.