Importing .stp files to Coreform_Cubit

Dear Community,

I am in the process of importing a .stp file to coreform_cubit, but it seems that the volume naming convention is not preserved after importing. I am attaching some screenshots for an illustration:

the left screenshot illustrates how the volumes were actually labeled using Inventor


the screenshot on the right illustrates how cubit interprets the volumes after importing

I can also provide the .stp file for further inspection (I am unable to upload right now because I get an error stating that new users cannot upload files to the forum).

Any suggestions on how to overcome this issue would be gratefully accepted!

Best regards,

Your Cubit tree view indicates that there are sheet bodies as well as volumes. Expand the sheet body item and see if the named objects are there.

Just as a general note, there are certain naming conventions in Cubit. For example, a dash (-) cannot be used in a Cubit name because it can also be parsed as a minus sign.

Sheet bodies are an open set of one or more surfaces. They do not define a closed volume during import.

I am looking into what needs to be done so that you can upload a file.


1 Like (80.4 KB)

Great thanks!

I tried to upload my model as a .zip file along with this message.



I found that Cubit somehow preserves the names of the volumes but in a mysterious way, i.e. the names do not necessarily correspond to the associated volumes and there exists some kind of a mix up…

I tried importing my model with a variation of importing options, I am not sure why but by omitting the "sort" option there was a better correspondence between labels and volumes (there still existed some sheet bodies which didn’t contribute to a particular volume).

Let me know if you need further clarifications @karl.

Best regards,

Hi Nikos,

One of the reasons for using names is because we can’t guarantee that id numbering will be consistent between various CAE programs, especially when translated to a neutral file format such STEP.

One of the things that I noticed is that volume 7 and 14 occupy the same volume. You probably need to do a Boolean subtract between the two volumes maybe with a keep option if the interior volume is a separate part.

The overlapping volumes should not have impacted the data translation.

If all the volumes capture the model, I would recommend deleting the sheet bodies. They will just make the meshing process more confusing.

Karl (77.7 KB)
Hi @karl,

I used the importing options that can be found in the screenshot below (the volume labels assigned are also visible).

What options did you use for importing because no volumes in my model are associated to the labels “Volume 7” and “Volume 14”?

I am also providing the .stp file I imported with a .zip extension.

Best regards,

Interesting. I am running Coreform Cubit 2021.5. Nothing should have changed with the STEP import for several releases. I used the same options on import as you did. I also tried using the import attributes. option. What OS are you running?

My import is missing the dewar_volume. I am assuming that corresponds to my Volumes 7 and 8.


With your new STEP file I get the correct volume names. Is volume 8 part of the model? If it is you may still need to do a boolean because these volumes are overlapping.

Hello again @karl,

the CAD software that produced this .stp file (Inventor 2019) did not detect any overlapping between volumes, i.e. “Volume 8” and “dewar_solid” should not touch.

Note that “Volume 8” was originally labeled as “cryostat” but Cubit did not preserve the label for some reason.

To get a better picture “Volume 8” can be seen as a shell shielding the volume “dewar_solid”. The “dewar_solid” volume is the compact interior of the green region highlighten in your screenshot above. So they shouldn’t intersect at all…

A boolean operation between the two aforementioned volumes is not especially helpful because the volumes will be processed / grouped afterwards and different materails will be assigned to each.


That makes sense. For some reason, the STEP translator did not recognize cryostat as a closed volume. I will look into this a bit more.

1 Like

Does this image show what you are looking for? The dewar_solid is one material and internal to the cryostat that is a separate material? From a meshing point of view, I have to have distinct boundary on the cryostat that is shared by the boundary of the dewar_solid. The solids must be manifold. I produced this mesh with the following commands and then turning on the clipping plane so we could see the internal tetrahedral mesh and structure.

import step "C:/Users/karl/Downloads/Cryostat_assy_simplified (1)/Cryostat_assy_simplified.stp" heal
remove overlap volume 1 8 modify larger
separate body 8
delete Volume 62
imprint volume 1 63
merge volume 1 63
vol all scheme tetmesh
mesh vol 1 63
draw tet all

Hello @karl,

thank you for your support on this matter.

Indeed different materials correspond to the “cryostat” and “dewar_solid” volumes. The issue I can notice in the screenshot you provided is the fact that the “cryostat” volume should not contain the interior of the 2 cylinders within the outer shell.

The two cylinders should be hollow and their walls should have a thickness of 2mm or so. I am under he impression that cubit has properly imported the volume that corresponds to the cryostat (see attached screenshots).



Hi again @karl,

after repeating the procedure you indicated I found that the angle of your screenshot made it look like the cylinders where compact, but in fact they are hollow like they should be. Please ignore my previous post, I will let you know if I face further difficulties on this matter.