For the economic use of repair in the spare parts business, additive repair by Laser Powder Bed Fusion (LPBF) is a promising technology. As material can only be applied to a flat surface in LPBF, prior machining is required. The selection of the section plane requires expert knowledge, though. To provide that knowledge and recommend a suitable section plane, an expert system can be used. In this paper, a concept for such an expert system is presented and its functionality is evaluated by an example.