Using the Inertia tool, you can quickly see and export several attributes, including the Bounding Box dimensions for the overall assembly and all components. You can also create geometry for CG in a separate part or an existing one.
Is true that CATIA does not always provide the minimum Bounding Box volume, depending on how the part was created. To do this, you must get/create at least two lines conveniently, and create the BBox related to them by macro or power copy. The export file is good when you don't have complex geometry created mostly in context. This means to go through the structure and do all those operations more or less manually. Is feasible and can be done, creating also parameters which then can be export all of them from the assembly level in one shot in a csv file. But for a simple structure with simple parts, CATIA export is by far the most convenient solution.
