When are expressions automatically created in NX Design?

Expressions are automatically created in NX Design predominantly when features are created. This happens because when you design a model in NX, many of the parameters and dimensions associated with features—like holes, extrusions, and cuts—are defined through expressions. These expressions allow for controlling the geometry of the model more effectively, enabling dynamic updates and modifications as the design changes.

Each time a new feature is added, NX generates corresponding expressions to manage the feature’s characteristics, such as size, position, and relations to other elements. This practice ensures that the design intent is preserved and can be easily adjusted without requiring manual updates across various aspects of the model.

In contrast, options like model import, part revision, and opening a file do not typically lead to the automatic creation of expressions. When importing a model, for instance, existing expressions may be brought in, but new expressions are not automatically generated during this process. Similarly, revising a part or opening a file might involve checking or updating existing expressions, but does not create new ones automatically.