A mixing and extrusion machine (10) for the manufacture of rubber mixtures includes a mixer with a converging conical twin-screw (12) with a fixed frame (14) that supports sleeves (16). Two screws (18), being mounted at an angle, are mounted in the mixer (12) in such a way as to move in translational movement between an opening (22) arranged upstream and an outlet (25) arranged downstream of the sleeves. The screws are mounted in the sleeves with removable doors including sliding shutters (40) installed relative to the outlet (25). The sliding shutters move linearly between a closed position, in which the sliding shutters prevent the mixer from discharging the mixture, and an open position, in which the sliding shutters prevent discharge of the mixture through the sides of two counter-rotating rollers (32) of a roller nose type system located just downstream of the outlet.