In order to repair a workpiece, a requirement specification about a requirement to be met by the workpiece and a numerical simulation model for simulating a physical behavior of the workpiece are imported. Furthermore, a current shape of the workpiece is detected by means of a sensor. Where a deviation of the current shape from a target shape S of the workpiece is identified, a respective physical behavior of the workpiece in its current shape and in a shape added to by means of a 3D printer are simulated using the simulation model. Furthermore, a check is performed on the basis of the requirement specification to ascertain whether the simulated physical behavior meets the requirement. Depending on the outcome of the check, the workpiece is then either left in its current shape, added to by the 3D printer or discarded.