Moulding unit for manufacturing a container from a part-finished form made of plastic, this moulding unit comprising: - a mould equipped with a wall defining a cavity in the impression of the container and with an insert able to move with respect to the wall between a retracted position, in which it is retracted with respect to the cavity , and a deployed position, in which it projects at least partially into the cavity ; - at least one boxing system comprising a ram provided with a ram body , with a piston and with a rod rigidly attached to the piston and to which the insert is fixed, the rod and the piston being able to move as one between a retracted position corresponding to the retracted position of the insert , and a deployed position corresponding to the deployed position of the insert , the ram body and the piston jointly defining, one on each side of the piston , a primary chamber connected, via a primary fluidic circuit , to a primary source of fluid at a primary pressure (P1), and a secondary chamber connected, via a secondary fluidic circuit , to a secondary source of fluid at a secondary pressure (P2) that is comparatively lower, this moulding unit being characterized in that the boxing system comprises: - at least one electrically-operated valve mounted on the primary fluidic circuit , this electrically-operated valve comprising a fluidic outlet connected to the primary chamber and defining a bore section (S) that can vary according to an electric control signal ( E ) applied to the electrically-operated valve ; - a processing unit connected to the electrically-operated valve and programmed to cause the electric control signal ( E ) applied thereto to vary. - a mould equipped with a wall defining a cavity in the impression of the container and with an insert able to move with respect to the wall between a retracted position, in which it is retracted with respect to the cavity , and a deployed position, in which it projects at least partially into the cavity ; - at least one boxing system comprising a ram provided with a ram body , with a piston and with a rod rigidly attached to the piston and to which the insert is fixed, the rod and the piston being able to move as one between a retracted position corresponding to the retracted position of the insert , and a deployed position corresponding to the deployed position of the insert , the ram body and the piston jointly defining, one on each side of the piston , a primary chamber connected, via a primary fluidic circuit , to a primary source of fluid at a primary pressure (P1), and a secondary chamber connected, via a secondary fluidic circuit , to a secondary source of fluid at a secondary pressure (P2) that is comparatively lower, - at least one electrically-operated valve mounted on the primary fluidic circuit , this electrically-operated valve comprising a fluidic outlet connected to the primary chamber and defining a bore section (S) that can vary according to an electric control signal ( E ) applied to the electrically-operated valve ; - a processing unit connected to the electrically-operated valve and programmed to cause the electric control signal ( E ) applied thereto to vary. <EOS>