A machine to manufacture cartridges for electronic cigarettes comprising a casing made of plastic material having a microperforated bottom wall and a side wall and containing a quantity of powdered tobacco on top of which a portion of filtering material is arranged; the manufacturing machine comprises: a feeding conveyor which feeds a plurality of empty casings in correspondence to a collecting station; a drum rotating at a predetermined pitch around its own vertical rotation axis, which receives an orderly mass of empty casings from the feeding conveyor in correspondence to the collecting station and feeds them to a filling station, where a quantity of powdered tobacco is inserted into each empty casing; a filling unit arranged in correspondence to the filling station for feeding a quantity of powdered tobacco inside each empty casing from above; the filling unit comprising a first hopper for the collection of powdered tobacco; the manufacturing machine being characterized in that said filling unit comprises a plurality of discs (32, 34, 40, 42) arranged under the first hopper and designed to fill the empty casings with the powdered tobacco, said discs being arranged to be brought into rotation at a predetermined pitch about a common vertical rotation axis; the first disc defining a bottom wall for the first hopper; wherein between the first disc and a second disc a plurality of compartments is defined, each designed to contain the quantity of powdered tobacco to be inserted into a respective casing from above; wherein the first disc and the second disc are mobile relative to one another, so as to vary the volume of the compartments and the quantity of powdered tobacco contained inside them and wherein the plurality of discs (32, 34, 40, 42) of the filling unit are arranged to be brought into rotation while the drum transfers the casings containing powdered tobacco to a weighing and discarding station in correspondence of a unit for weighing the cartridges containing powdered tobacco and for the possible discarding of the cartridges which do not conform. a feeding conveyor which feeds a plurality of empty casings in correspondence to a collecting station; a drum rotating at a predetermined pitch around its own vertical rotation axis, which receives an orderly mass of empty casings from the feeding conveyor in correspondence to the collecting station and feeds them to a filling station, where a quantity of powdered tobacco is inserted into each empty casing; a filling unit arranged in correspondence to the filling station for feeding a quantity of powdered tobacco inside each empty casing from above; the filling unit comprising a first hopper for the collection of powdered tobacco; the manufacturing machine being characterized in that said filling unit comprises a plurality of discs (32, 34, 40, 42) arranged under the first hopper and designed to fill the empty casings with the powdered tobacco, said discs being arranged to be brought into rotation at a predetermined pitch about a common vertical rotation axis; the first disc defining a bottom wall for the first hopper; wherein between the first disc and a second disc a plurality of compartments is defined, each designed to contain the quantity of powdered tobacco to be inserted into a respective casing from above; wherein the first disc and the second disc are mobile relative to one another, so as to vary the volume of the compartments and the quantity of powdered tobacco contained inside them and wherein the plurality of discs (32, 34, 40, 42) of the filling unit are arranged to be brought into rotation while the drum transfers the casings containing powdered tobacco to a weighing and discarding station in correspondence of a unit for weighing the cartridges containing powdered tobacco and for the possible discarding of the cartridges which do not conform.