PolyNURBS fitting for a large structural connector with multiple integrated fixed components

Giovanni_barreca

I have successfully optimized the structure; however, I am struggling to generate a functional geometry from the results. Before I attempt to manually reconstruct the NURBS, do you have any suggestions? My primary issue is shrinkage at the fixed interfaces, and the resulting NURBS surface is often non-manifold or open-edged. I have experimented with various mesh-processing tools, but I haven't achieved a viable solution yet. I'd like to obtain the results in https://help.altair.com/inspire/en_us/topics/inspire/structure/fit_polynurbs_c.htm,with intersect. For context my part is 400mm high and of a diameter of 150mm, the common dimension of a fixed geometry is 8mm

SouravDas0306

Hello Giovanni,

You have successfully optimized the structure, but the main difficulty now is obtaining a clean, functional geometry from the topology result, especially around the fixed interfaces. Since your part is relatively large (400 mm height and 150 mm diameter) compared to the 8 mm fixed features, the shrinkage you are seeing is likely caused by insufficient mesh resolution and smoothing effects near the constrained regions. Before manually reconstructing the NURBS, I would suggest refining the mesh locally around the interfaces, adding non-design buffer zones, and possibly oversizing the preserved geometry slightly to compensate for erosion during optimization. In many cases, the PolyNURBS “with intersect” workflow works best only after the topology result has been converted into a fully watertight manifold mesh, because open edges, thin necks, and self-intersections near supports often cause invalid NURBS patches. A practical workflow is topology result > remeshing/cleanup > watertight manifold mesh > PolyNURBS fitting. Also, if the interfaces are function-critical, it is generally better to preserve them as CAD/non-design geometry and optimize only the transition regions. Given your dimensions, I would also recommend ensuring at least 3–5 elements across the 8 mm interface regions, otherwise shrinkage and non-manifold reconstruction issues are very difficult to avoid.

Regards,

Sourav