One of the application areas crying out for high quality digital twins are Additive Manufacturing (AM). Traditional CAD-based on boundary structures (b-rep) targets subtractive and formative manufacturing where material properties are assumed to isotropic and the interior of the object to be a solid block. AM allows advanced interior structures to be produced, e.g., lattice structures. Trying to represent lattice structures in b-rep CAD most often makes the b-rep CAD-system kneel. Certain AM-technologies allows graded material to be build. Graded material is not supported by b-rep CAD.
CAD designed objects to be produced by AM are most often converted to an STL-files (a triangulation). Then the STL representation is modified to prepare for actual manufacture, i.e., by adding interior structures and modifying the geometry be suitable for the AM-process targeted. The result is that the original CAD-model is no longer an accurate digital twin of the object produced. To update the CAD-model to represent the shape of the object produced is hard. This is both due to thermal distortions in the object produced as well as the challenge of updated a b-rep CAD-model to match a STL-file or a point cloud acquired by metrology.
Some of the above challenges were addressed in the CAxMan RIA (2015-2018), see www.caxman.eu for more details.