Abstract: A machine for making mould cores from flowable sand mixtures in hot multi core boxes including a supporting frame carrying a conveyor whereon core boxes are placed, each of the boxes having a top and a bottom piece and mechanically interlinked main and additional gates. The gates are adapted to close or open respectively the central and peripheral core print openings of the core boxes while interacting with their respective individual drives. When the main gate and one of the additional gates interact with their respective individual drives made fast on the supporting frame at the pressing mechanism, they close respectively the central and peripheral core print openings. When the main gate and the other additional gate interact with their other individual drives made fast on the supporting frame before the splitting-up mechanism, they open the central and peripheral core print openings.