Multilayer core molding method

A multilayer core molding method for molding a multilayer core of a golf ball, the multilayer core molding method comprising:

• an upstream process of obtaining an intermediate molded body;
• and
• a downstream process of performing molding using a downstream process molding apparatus, wherein
• the intermediate molded body includes:
• an inner core;
• and
• an unvulcanized or semi-vulcanized first outer core material that covers only part of a surface of the inner core and is integrated with the inner core,
• the downstream process molding apparatus includes:
• a first downstream process mold including a substantially hemispherical first downstream process mold cavity surface;
• a second downstream process mold including a substantially hemispherical second downstream process mold cavity surface;
• and
• an intermediate plate including a substantially hemispherical intermediate plate cavity surface configured to be arranged facing the first downstream process mold cavity surface, and a substantially hemispherical intermediate plate projecting surface configured to be arranged facing the second downstream process mold cavity surface, and wherein
• the downstream process includes:
• a second outer core arrangement step of arranging a second outer core material on the second downstream process mold cavity surface or the intermediate plate projecting surface;
• an intermediate molded body arrangement step of arranging the intermediate molded body on the intermediate plate cavity surface or the first downstream process mold cavity surface;
• and
• a preparatory molding step, performed after the second outer core arrangement step and the intermediate molded body arrangement step, of compression-molding the second outer core material and the intermediate molded body, in a state in which the first downstream process mold, the second downstream process mold, and the intermediate plate are closed against each other,
• in the preparatory molding step, part of the first outer core material of the intermediate molded body sticks out from between the first downstream process mold cavity surface and the intermediate plate cavity surface to form a first flash, and part of the second outer core material sticks out from between the intermediate plate projecting surface and the second downstream process mold cavity surface to form a second flash,
• the first flash and the second flash each includes a thick portion and a thin portion, the thin portion of the first flash couples the first outer core material of the intermediate molded body and the thick portion of the first flash, and the thin portion of the second flash couples the second outer core material and the thick portion of the second flash.