About Regenerating Models
When Creo Parametric regenerates a model, it recreates the model feature by feature, in the order in which each feature was created, and according to the hierarchy of the parent-child relationship between features. In an assembly, component features are regenerated in the order in which they were created, and then in the order in which each component was added to the assembly. Creo Parametric regenerates a model automatically in many cases, including when you open, save, or close a part or assembly or one of its instances and when you open an instance from within the Family Table. You can also use the Regenerate command to manually regenerate the model.
The 
Regenerate command located on the Model tab allows you recalculate the model geometry incorporating any changes made since the last time the model was saved. If no changes have been made, the system informs you that the model has not changed since the last regeneration. In general, it is a good idea to regenerate the model every time you make a change, so that you can see the effects of each change in the Graphics window as you build the model. Regenerating often helps you stay on course with your original design intent by helping you to resolve failures as they happen.
Regenerate command located on the Model tab allows you recalculate the model geometry incorporating any changes made since the last time the model was saved. If no changes have been made, the system informs you that the model has not changed since the last regeneration. In general, it is a good idea to regenerate the model every time you make a change, so that you can see the effects of each change in the Graphics window as you build the model. Regenerating often helps you stay on course with your original design intent by helping you to resolve failures as they happen.You can use Regenerate to find bad geometry, broken parent-child relationships, or any other problem with a part feature or assembly component.
When an active model requires regeneration, the regeneration 
icon appears on the status bar.
icon appears on the status bar. | To make model regeneration process more efficient, the individual features or components are regenerated on need basis. When a feature or component cannot be regenerated for any reason or if regeneration is not required, the features or components are restored to their last regeneration status. |