""""""""So the conclusion is I need to repair some bad area manually or request to our client STEP format.""""""""""

Yes and all the other "Solids formats like SAT. I would also think that with this info, there may be some functions in NX to "Prepare to export" like some kind of analisys and repair on the "Native geometry" BEFORE the export.

Some of the things Michael is describing here are "functions of import" and just how the process works with the data and parameters presented.

If all you have is this file, it will need to be worked. Actually, the program I used has "2 different methods of importing of iges and produced 2 different results. Possibly the STEP or SAT imports may handle things better. Michael even just discussed manually changing the tolerance value in the iges file to get a different result that may produce a model that is easier to repair on import.....

The other thing is you mention you want to do Core and Cavity. I'm no expert on this, but it would seem to me you want to do parting lines anyway...So halving the model into 2 seperate surfaces may make for a better resulting import or easier to fix whats left????

Burr