This article shows the application of Knowledge Based Engineering (KBE) methodology for the design automation of the structure of an automotive painting defects inspection tunnel. A previous work reached the design automation through the data transfering from Spreadsheets to Siemens NX CAD software using applications programmed with Visual Basic. With the application of KBE, it was possible to control the geometrical features of every part in the tunnel, to properly manage the component addition to the assembly and to reach a direct interaction between the designer and the CAD tunnel model in a new and more insightful manner. The presented work was developed through Knowledge Fusion (KF), a Siemens NX module which is based in Knowledge Based Engineering (KBE).