A device to correct geometrical differences of surfaces of parts to be assembled at the interface of the assembly. A measurer to acquire data by measuring the geometry of the assembly surfaces of two parts to be assembled to each other with their respective assembly surfaces facing. A simulator configured to simulate the assembly of the parts and to determine from the acquired data at each measured point of a sampling of the interface a thickness of the void resulting from the geometrical discrepancies between the assembly surfaces. An additive fabricator to receive from the simulator data representative of the thicknesses of the voids resulting from the geometrical discrepancies between the assembly surfaces. The additive fabricator configured to deposit material on the assembly surface of at least one of the parts to at least partly fill the void resulting from the geometrical discrepancies between the assembly surfaces.