PURPOSE: To obtain molds capable of manufacturing a frame assembly having an adhesive piece integrally provided to the inner surface side of its box-like container, consisting of a fixed mold, a movable mold and a side core piece to form holes and ribs in the adhesive piece on the inner surface side.

CONSTITUTION: A resin material is injected into molds for forming a speaker box 10, for example, and then a side core piece 23 consisting of a shaft pin 20 and a rib piece 21 to form holes in an adhesive piece 11 is lowered by an oil-pressure cylinder 24 before a fixed mold 12 and a movable mold 14 are opened. A push plate 16 is then operated to separate a molding 26 from a movable insertion body 13 by an ejector pin 17. In this case, an undercut part 25 of an adhesive piece form is forcibly punched out to obtain an objective molding integrated with an adhesive piece 11.

USE: Formation of speaker box, etc.