A method of manufacturing at least one multi-layer preimpregnated preform (4, 24, 26), characterized by the steps of: a. Arranging a plurality of preforms (4, 24, 26) of dry semi-finished products or dry fabrics b. Applying resin (3, 25, 27) locally on the at least one preform (4, 24, 26) of dry semi-finished products or dry fabrics with quantities depending on the local thickness of the at least one preform (4, 24, 26) of dry semi-finished products or dry fabrics in at least one liquid tight rigid first vacuum chamber (9, 28, 29) or applying resin (3, 25, 27) locally on at least one preform (4, 24, 26) with quantities depending on the local thickness of the preform (4, 24, 26) of dry semi-finished products or dry fabrics outside the at least one liquid tight rigid first vacuum chamber (9, 28, 29) and putting the at least one preform (4, 24, 26) applied with resin (3, 25, 27) in the at least one liquid tight rigid first vacuum chamber (9, 28, 29) before closing said at least one first vacuum chamber (9, 28, 29), c. Tightening the at least one first liquid tight rigid vacuum chamber (9, 28, 29), d. Removing at first air from at least one second rigid vacuum chamber (13, 21, 22) interacting with the first liquid tight rigid vacuum chamber (9, 28, 29) via a vacuum foil/flexible membrane, e. Removing subsequently air from the at least one first liquid tight rigid vacuum chamber (9, 28, 29) to the same pressure as in the at least one second vacuum chamber (13, 21, 22) or slightly above in order to remove any air from the at least one preform (4, 24, 26) of dry semi-finished products or dry fabrics, f. Increasing the pressure in the at least one second vacuum chamber (13, 21, 22) to press the resin (3, 25, 27) into the at least one preform (4, 24, 26) in the at least one first liquid tight rigid vacuum chamber (9, 28, 29); and g. Demoulding the at least one multi-layer preimpregnated preform (4, 24, 26) from the first liquid tight rigid vacuum chamber (9, 28, 29); wherein a first vacuum port is provided with a valve to control pressure in the first left hand vacuum chamber and in the first right hand vacuum chamber; wherein the vacuum foil is fixed and tightened laterally into each of the left hand lateral wall and the right hand lateral wall to define with the upper rigid plate and the intermediate wall the second left hand vacuum chamber and the second right hand vacuum chamber of the device; and wherein each of the second left hand vacuum chamber and of the second right hand vacuum chamber are provided with respective second vacuum ports (32, 33) controlled by respective valves (34, 35) to define individually the pressure in the second left hand vacuum chamber and in the second right hand vacuum chamber separately from the pressure in the two first liquid tight rigid vacuum chambers (28, 29). a. Arranging a plurality of preforms (4, 24, 26) of dry semi-finished products or dry fabrics b. Applying resin (3, 25, 27) locally on the at least one preform (4, 24, 26) of dry semi-finished products or dry fabrics with quantities depending on the local thickness of the at least one preform (4, 24, 26) of dry semi-finished products or dry fabrics in at least one liquid tight rigid first vacuum chamber (9, 28, 29) or applying resin (3, 25, 27) locally on at least one preform (4, 24, 26) with quantities depending on the local thickness of the preform (4, 24, 26) of dry semi-finished products or dry fabrics outside the at least one liquid tight rigid first vacuum chamber (9, 28, 29) and putting the at least one preform (4, 24, 26) applied with resin (3, 25, 27) in the at least one liquid tight rigid first vacuum chamber (9, 28, 29) before closing said at least one first vacuum chamber (9, 28, 29), c. Tightening the at least one first liquid tight rigid vacuum chamber (9, 28, 29), d. Removing at first air from at least one second rigid vacuum chamber (13, 21, 22) interacting with the first liquid tight rigid vacuum chamber (9, 28, 29) via a vacuum foil/flexible membrane, e. Removing subsequently air from the at least one first liquid tight rigid vacuum chamber (9, 28, 29) to the same pressure as in the at least one second vacuum chamber (13, 21, 22) or slightly above in order to remove any air from the at least one preform (4, 24, 26) of dry semi-finished products or dry fabrics, f. Increasing the pressure in the at least one second vacuum chamber (13, 21, 22) to press the resin (3, 25, 27) into the at least one preform (4, 24, 26) in the at least one first liquid tight rigid vacuum chamber (9, 28, 29); and g. Demoulding the at least one multi-layer preimpregnated preform (4, 24, 26) from the first liquid tight rigid vacuum chamber (9, 28, 29);