Reply To: Challenges with Importing Complex Geometries into ANSYS APDL

[Gary Stofan]

Here are some additional suggestions from back in 2004 when APDL Solid Modeling was already in the mature phase. (No further development or defect corrections.)

What are the known problem areas?
Some of the known problem areas in solid modeling include:
- working with “dirty” geometry, either imported or created inside ANSYS
- merging meshed entities (NUMMRG, xGLUE, xADD, xSBy, etc.)
- Boolean operations performed on multiple entities at the same time
- clearing and remeshing (xCLEAR)

What is the workaround if an error is encountered?
If a defect or error is encountered, you may CDWRITE the model out and read it back in using the ANF
format (CDOPT,ANF) to get a “clean” copy of the current geometry. Follow the best practices in the next
section in order to overcome the initial difficulty or use an alternative method to obtain the same result.

What are best practices?
Some of the “best practices” that have been gathered over the years that, in most cases, will yield a
Boolean-able and meshable solid model include:
Before exporting the solid model to ANSYS (if applicable):
-  divide and/or merge the model in the CAD system (rather than in ANSYS) before importing
-  use tight tolerances in the CAD system before exporting to ANSYS
- use the CAD system’s geometry checker to verify the CAD data; alternatively, export the
geometry and re-import it into the CAD system
-  use the Connection add-on for the CAD system rather than IGES to import the geometry

In ANSYS:
-  perform any solid modeling operations prior to any meshing operations
- use the “input file” approach rather than working totally interactively since input files are
readily edited and reduce the risk of have only a “corrupted” database to work with
- if interactive, use SAVE liberally to always have a valid model to go back to in case of
encountering a failure in an operation
- SAVE the unmeshed solid model and RESUME it rather than relying on xCLEAR to
cleanly remove the mesh
- perform Boolean operations an entity at a time rather than all at once
- merge nodes before merging keypoints if the entities are already meshed