FreeCAD filling in holes by itself

[ChrisFC]

Hi all,

OS: Ubuntu 20.04.5 LTS (ubuntu:GNOME/ubuntu)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.19.2)
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/United Kingdom (en_GB)

Apologies that I cannot provide a file to work with, due to the work I am doing being commercially sensitive, as such, I will describe my problem.

One of the engineers in our team has provided me with some CAD in the form of a STEP file, produced by a non-FreeCAD piece of software. The CAD is of a somewhat slab-esque object that contains a few holes in it. Upon loading said STEP file with FreeCAD, some (but not all) of these holes are changed - some of them become 'sealed' as if the open end of the hole has a thin circular disc closing the end of the hole, that simply is not there in the original STEP file, as viewed in the CAD software used to produce it (in fact, this issue only seems to happen when loaded up with FreeCAD). Some of the other holes become partially closed.

Bizarrely, some of the holes which (correctly) do not become covered will go on to become covered when I export the CAD to a step file and load it back up using FreeCAD. This is frankly bizarre behaviour, and I would wish for this to stop if possible. I have already tried toggling the compound-merge tick box on and off in the STEP file import/export preferences with no luck.

Any help/ideas/thoughts would be appreciated.

Cheers,
Chris

[papyblaise]

is it a consequence of brexit you can no longer share your file with the rest of the world
you say "open the STEP file" you do a simple opening or an Import

[ChrisFC]

Erm, not sure what this has got to do with Brexit? But no, as I stated I unfortunately cannot share it. With regards to opening the file, I have tried both File>open and File>import with no difference.

Cheers,
Chris

[papyblaise]

Ahh , can you ask the person who provided you with the STEP to simplify it to just the buggy holes, and try to open it, and if it doesn't work, he might be anonymous enough to join it
to have effective help you will have to take the courage to send it to us (it will remain between us, just forum readers )

[chrisb]

A common mistake is to select more than one object (or feature) for export, so that existing holes can be closed.
If the step file has errors, try to open it in VariCad viewer and re-save it.