Mold core of multi-inner-cavity rotary body structure piece

The utility model relates to a mold core of a multi-inner-cavity rotary body structure piece. The mold core comprises a sand core base embedded into the top of lower box molding sand; a bottom sand core is overlapped at the center of the upper end face of the sand core base; a middle sand core is overlapped above the bottom sand core; a top sand core is overlapped above the middle sand core; the sand core base, the bottom sand core, the middle sand core and the top sand core are coaxial; the shape of the bottom sand core is the same as that of a lower rotary inner cavity of a structure piece; the shape of the middle sand core is the same as that of a middle rotary inner cavity of the structure piece; and the shape of the top sand core is the same as that of an upper rotary inner cavity of the structure piece. A mandrel is arranged at the center of the sand core and comprises a mandrel main rod, and a mandrel concave end and a mandrel convex end which are connected with the two ends of the mandrel main rod; and the mandrel convex end on the upper side can be inserted into the mandrel concave end on the lower side. A core box comprises a core box bottom plate and a core box side plate; and the mandrel is inserted into the center of the core box bottom plate. By virtue of the mold core of the multi-inner-cavity rotary body structure piece, a complicated inner cavity structure of a large-size multi-section high-precision rotary body casting is formed.