The invention regards a system and method for assisting reductive shaping of an object into a desired 3D-shape by removing material. The system comprises a tool and a localization means. The tool is configured to remove material from an object by means of a cutting function or a grinding function performed by a working head of the tool. The localization means determines a position of the working head relative to the desired 3D-shape. Each time the grinding function or cutting function would remove material from an inside of the desired 3D-shape the cutting or grinding function is deactivated.
