I have had the same kind of problems, here is what i do to make the export of my files:
1. Open the part you want to make a igs / stp of.
2. Right click on the body and click copy (keep the window open)
3. Make a new part.
4. Right Click on the new part and select paste special
5. In the paste special dialog box select AsResultWhitLink and click OK
6. Now you got a new solid whit link to the previous part, right Click on the solid and select Isolate to break all links.
7. Save the new part whit a different name.
8. Close Catia.
9. Open Catia Again
10. Open the new part (the one whit the solid whiteout link)
11. Save this part as igs or stp

This is the way i have been lucky to make the most of my iges or step files.

Hope that it helps.

Best regards

Moldkon,

Thanks for your reply.
But I got another problem.I cannot change the setting on the dialog box to be paste with link. It selected paste.
Do you know how to change the setup so I can change the setting to paste with link. Thanks again

And by the way, I am doing this on assembly, exporting igs
and step files.

I´m not quit sure that you can use the approach in copying all the parts in an assembly so you can make an iges or step, i have only tried to make part files to put in our cam system.
About the dialog box : I must admit that i do not have an idea about changing the settings, but have you selected the paste special and not only the paste when you right click on the body.

Sorry that i could not be more helpful in this question.

Best regards

Convert a surface model in V5 to iges (surface and wireframe).
1.Create a new OpenBody and make sure it is emty and active.
2.Isolate the history (specifictions).
Use the command dissasemble in operations in GSD or wireframe and surface design. Choose dissasemble all.
2. Now You should see all the isolated surfaces in the new open body.
3. Delete all the other bodies. (this keeps only the isolated surfaces)
4. Save as iges.

If you want to convert I solid to iges:
1. Extract the surfacecs from the solid withe the extract command in the operations within GSD or wireframe and surface design.
2. do the same as above (converting a iges from surface)

Let's be honest : STEP and IGES are not working really good with CATIA V5 but I heard they are making a lot of progresses for their new V5R8 release.
I still have problems with V5R7 with the assemblies but it should be fixed with CATIA V5R8.

if not in release 8...maybe release 9??

We had the same problem writing or importing STEP files into Catia V5,
until we purchased a step translator lincense.