Learning Forum

[paris.alford]

Hi all,

I've been having trouble with an STL file of femur cartilage which was exported from an MRI of a knee. Basically, I've been trying to convert the STL file to a solid (I've tried two methods - one by right clicking and converting to solid and clicking through entire repair tab, and the other method by shrinkwrapping about 0.5mm or less and then autoskinning). The converting STL to solid goes well, but when meshing using default options the mesh fails. 

The femur cartilage geometry is very thin, about 0.8mm in some parts, and 1.5mm in the majority. When importing to geometry, ANSYS warns about high order NURBS surfaces causing issues, and the surfaces which it warns about are consistently missing from the mesh later on (even when the mesh fails), unless I shrinkwrap using 0.1mm or less. 

I've determined that the high order NURBS surfaces are the issue and have looked through so many online forums and this forum for answers. I have tried all repair options available. I don't have access to Solidworks. How can I resolve this within ANSYS Workbench 23.1 (student version), Creo Parametric, Onshape or similar?

 

[peteroznewman]

Hi Paris,

I have some experience converting STL facet bodies from CT scans to geometry for meshing. Here are some videos to review:

https://youtu.be/Gj3bTd0aN8I

https://youtu.be/ARy7EvA3LTg

https://youtu.be/d4ZXSFjIAII

https://youtu.be/7jzWEiS1wtA

https://youtu.be/KWGVkilcMAE

I would be happy to have a look at your STL file and advise you if you are willing to share the file. If so, compress the STL file into a .zip format and upload it to a file sharing site such as Google Drive where you must set the file sharing so that Anyone with the Link can download it. Paste the link into your reply.

Regards,

Peter

[paris.alford]

Hi Peter,

Thank you for your quick reply! I ended up fixing my femoral cartilage model with the help of your videos, thank you. (I ended up increasing the shrinkwrap size.)

I was wondering if you had any information about finding holes in geometry (femur converted from STL to solid) which is showing as airtight in Spaceclaim but as quilt in Creo (and not uploading to Onshape). I have been following your video on separating cortical and cancellous bone geometry (

) but am running into issues with volume extract (due to the non-watertight geometry).