Method for molding a multi-component manufactured product through injection of plastic materials in a mold comprising on the inside one or more movable parts, characterized in that the movable parts are moved into a first configuration in which at least two distinct mold cavities are made in the mold, plastic material is injected into each of the two distinct mold cavities to form two components of the manufactured product, the movable parts are moved into a second configuration, in which they make at least a third cavity in the mold the walls of which at least partially consist of the two components already injected, plastic material is injected into the third mold cavity to form a third component of the manufactured product that is thus welded to the first two.