Building bug while intersecting a polar patterned pocket with a lofted profile

[openBrain]

Hi all,

Hope this is the right place to post.
I just found what looks like a bug.

I'm encountering a strange building behavior in the following case (I attached FCstd file as it would probably be easier to figure out) :
*1) I created a vertical (Z) lofted profile in a pad => OK
*2) I added a round pocket going through the whole part horizontally (X) => OK
*3) I set the previous pocket to (polar) repeat at an angle of 90° (Y) => Ouch => A bunch of surfaces (no thickness walls) appears where the pockets cross inside the part (and where I expect a complete void)

bug.png (91 KiB) Viewed 2304 times

* I tried replacing the polar repeat by a new pocket => no bug
* I tried the same polar repeating but applied inside a box created from a cube => no bug

I run Freecad 0.18 rev. 15159 installed from PPA on a up-to-date Kubuntu 18.04.

Hope this helps.

[chrisb]

Hi openBrain, welcome to the forum.
I moved your post to Help forum.

[openBrain]

Hi chrisb,

Thanks for welcoming.
Sorry for posting in the wrong sub-forum. I just read this before posting : https://forum.freecadweb.org/viewtopic.php?f=3&t=5236 (that could eventually be improved by pointing out this topic to be the right one for bug submission).
In the meantime I found that it was actually pointed out in this other webpage (that I previously missed) : https://www.freecadweb.org/wiki/Tracker

Please let me know if bug is confirmed.

BR

[chrisb]

I'm still testing, but I have already a comment on your sketching:

You found a very unconventional way of centering a circle in a rectangle. The common (easy!) way is to use symmetry on two diagonal corners and the center of the circle.

[chrisb]

The bug comes from the midplane pocket. If you want to get your model done, set midplane to false and create the polar pattern with 360 degrees and 4 copies.

I have simplified the example showing the issue: Change the pad's midplane property from true to false and it will succeed in no time, even with 4 occurrences at 360° - which yields the same as midplane+90°+2 occurrences.
Change back to midplane takes several minutes (toothbrushing plus getting in the pyjamas plus answering other posts!) and shows the error again.

Could you please create a bug report in the tracker and link to this discussion?

OS: macOS High Sierra (10.13)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.14976 (Git)
Build type: Release
Branch: (HEAD detached at e79a19828)
Hash: e79a19828e2e92269ff96110dfeadaa245ad17c2
Python version: 2.7.15
Qt version: 5.11.2
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Germany (de_DE)

[openBrain]

You found a very unconventional way of centering a circle in a rectangle. The common (easy!) way is to use symmetry on two diagonal corners and the center of the circle.

Indeed.
Actually this part isn't a real one. I was originally doing some kind of a "monkey test" to give a try at latest Freecad revision (that I finally found remarkable). You can notice that the use I did of the polar pattern would also be quite unconventional in a real life design.
I originally did that this way to find a feature similar to other CAD software where you can natively snap points to a line center point.
I wasn't particularly looking for bugs and I admit that I didn't clean the file before sharing it here.

The bug comes from the midplane pocket. If you want to get your model done, set midplane to false and create the polar pattern with 360 degrees and 4 copies.

Actually I don't need this part. I found a workaround, yours is also OK and there are probably others. I just want to share the bug so it could be patched to prevent potential issues for others.

Could you please create a bug report in the tracker and link to this discussion?

Saw that I need to create another account for the bug tracker. I'll do it in the coming days.

BR

[openBrain]

The strange thing is that it also has something to do with fact that some material is present or not where the repeated patterns cross.
In the attached file everything's OK as patterns cross in void space.
But just reduce the side length of the square pocket below 5 mm and problem appears...

BTW
OS: Ubuntu 18.04.1 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.15159 (Git)
Build type: Release
Branch: master
Hash: ba11c3a70109cdd0d15f84f3531565dd4ece5c50
Python version: 2.7.15rc1
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: French/France (fr_FR)

[chrisb]

Created bug report issue #3679.

[Kunda1]

Created bug report issue #3679.

@user1234 reports this is fixed. See issue #3679

[chrisb]

Fix confirmed, ticket closed.