Hello Author Doing, the text below is from OCC 6.5.0 documentation (Data Exchange IGES FORMAT User's Guide), it explain the supported version to IGES format, please check the documentation of OCC 6.5.1 and the IGES version of your model.
IGES files up to and including IGES version 5.3 can be read. IGES files that are produced by
this interface conform to IGES version 5.3 (Initial Graphics Exchange Specification, IGES 5.3.
ANS US PRO/IPO-100-1996).
This manual principally deals with two Open CASCADE classes:
• The Reader class, which loads IGES files and translates their contents to Open
CASCADE shapes,
• The Writer class, which translates Open CASCADE shapes to IGES entities and
then writes these entities to IGES files.
File translation is performed in the programming mode, via C++ calls, and the resulting Open
CASCADE objects are shapes.
All definitions in IGES version 5.3 are recognized but only 3D geometric entities are
translated. When the processor encounters data, which is not translated, it ignores it and
writes a message identifying the types of data, which was not handled. This message can be
written either to a log file or to screen output.