HFSS15: Four: Removing Small Features

Even though, in principle, the geometry may be ready for a mesh to be created, it is possible that small features in the geometry lead to a mesh that is unnecessarily large and contains long and thin tetrahedra that make the simulation converge slower. Small features may even cause the mesh generation to fail. By small, we mean details on an object that are thousands of times smaller than the main features of the object, and that, in most cases, are unintended consequences of the drawing history in another CAD tool. Therefore, it is advantageous to remove small features.

You may have noticed that you could have invoked small-feature removal at several earlier stages. There is no objection to doing it earlier. See Object Overlap Settings for Complicated Models. The reason why it is presented here as stage four is that the previous stages were necessary while this one is optional.

To start the small-feature removal:

1. Click HFSS>Modeler>Analysis Options and specify the Entity Check level, make selections for holes, chamfers, and blends, their thresholds, as well as for edges, faces and slivers.

2. Select objects and invoke object analysis through Modeler>Model Analysis>Analyze Objects.

Alternatively, without objects selected, use Modeler>Model Analysis>Show Analysis Dialog>Objects and select objects from the list. In the Model Analysis window, invoke Perform>Analyze Objects.

The software will report according to the Analysis Options settings, such as holes smaller than a given radius, the smallest edge length and the smallest face area.

3. Upon clicking OK, the analysis is performed.

As a result of the analysis, the software presents a list of all holes, chamfers, blends, faces and edges that don’t meet the thresholds set by you in the Analysis Options.

4. Check the box "Auto-Zoom to Selection" at the bottom of the Model Analysis window and click on items in the list.

Inspect them visually and decide whether they can be deleted. It is good practice to delete them one by one rather than deleting many at once in order to prevent unintended changes.

Sometimes, an edge or face cannot be deleted, and you get a message notifying you. In that case, either ignore it, or revisit it after deleting some other details first, or revisit it later manually in the 3D drawing environment.

At this point, the geometry has no ACIS errors, no non-manifold objects and no partial object intersections. Furthermore, there are fewer small features that were unintended or unimportant for the electromagnetic analysis, so the quality of the model has improved.