Rebuild is just rebuilding current configuration. Force Rebuild, rebuilds all Configurations. least that what I just read
thank you Todd.
See these help topics:
Rebuild only rebuilds features that have changed, whereas force rebuild rebuilds ALL features whether they have changed or not.
For instance, let's say you have a part that has 10 features. You double click on the 3rd to last feature and change a dimension (and don't hit rebuild). Then you double click on the last feature and change a dimension (and don't hit rebuild).
Now, if you hit the rebuild icon, it will rebuild the 3rd to last feature and the last feature; it may also rebuild the 2nd to last feature if that feature is a child of the 3rd to last feature.
If instead of hitting the rebuild button after changing those two dimensions, you use Force Rebuild, it rebuilds all 10 features regardless of whether anything has changed in the first 7 features.
For best performance, it is suggested to use the rebuild icon most of the time and it is good practice to use the force rebuild command every once in a while to make sure everything is clean and up to date. I wouldn't suggest using the force rebuild command as a replacement for rebuild unless you are working on simple parts that don't take a long time to rebuild.
One other case where you may want to use the Force Rebuild command is if you are using "Verification on Rebuild (enable advanced body checking)". See this help topic:
Force rebuilding with that option on will rebuild the model with extra body checking.
Most models don't require the extra body checking, hence why it is off by default. But some users making more complex models, especially surfacing type models, like to work with verification on rebuild always on. It makes rebuilding slower (and significantly so in some cases), but when working with complex features that have more chance of intersecting faces and other potential body issues, it ensures that everything is always clean. An alternative approach is to leave it off, but use Tools, Check every once in a while to make sure all is good and only use verification on rebuild if tools, check indicates there is a problem (or you visually see a problem even without tools, check).
I hope this helps,
thank you Jim, for the detail content.