Abstract: A computer-implemented method for creating a customized CAD model of a casting mold, defined as the casting mold CAD model, for moulding of a personalized device, where the casting mold is used for casting an at least partly soft mould as part of the personalized device, and where the casting mold is adapted to be manufactured by means of rapid prototyping, such as 3D printing, including the steps of: —acquiring an input 3D model representing the personalized device, where the input 3D model is acquired by means of 3D scanning, —generating the casting mold CAD model as an impression of at least a part of the input 3D model, said casting mold CAD model thereby including the negative geometry of the personalized device, and—defining at least one sectioning of the casting mold CAD model by means of at least one separation plane and/or separation spline.