broken sketch?

[freman]

Hi,

I am trying to reuse a sketch I have used successfully, on a second part.

I imported the geometry ( which turned the one real construction,a circle, into a ref circle ). I added a constructed circle as the only real feature.

I then attached the sketch to the active object : Body001 and tried to make a pocket. It fails:

Failed to validate broken face.

I'm lost as to what is going on here. Can someone enlighten me?

thanks.


OS: Fedora 31 (Thirty One) (LXDE/LXDE)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.23873 (Git)
Build type: Release
Branch: master
Hash: eb6167ff89bc2b287c83d726dfcd52b775d1757e
Python version: 3.7.9
Qt version: 5.13.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/United Kingdom (en_GB)

[chrisb]

You have two circles in your sketch, both having identical diameter and common center. Delete one of them.

[Bance]

( which turned the one real construction,a circle, into a ref circle )

Why do you think this?

[freman]

Thanks Chris, that was it.

( which turned the one real construction,a circle, into a ref circle )

Why do you think this?

Because, when I imported the geometry, everything was mid blue colour including the circle. I tried to pocket and it said the sketch was empty. Seeing everything was blue, I was not sure why but concluded the import had converted it, so I added a real circle and made it "=".

Now I've deleted the new circle it works fine. There must have been a confounding problem which I've fixed in the meantime.

Many thanks for the help. I now have my pocket and I can get on.

[jimmihenry]

Hello, i am on a Windows 7 x64 machine. And i wonder if someone else is aware of a possible partly broken sketcher. Had
suddenly recognized odd behavior designing circles in addition with symmetry, tracing linked edges gave me also a orange
sketch. I noticed this behavior since additional colors were introduced. Don't have precise examples for now...
But something is fishy. <°)))))><

[Bance]

If the sketch turns orange you have redundant constraints ( the last one added is either unnecessary or conflicts with someother )

You should make a separate Thread for this as it is unrelated, and might prove useful as a new topic.

[chrisb]

Arcs and symmetry are often used wrong, and it sometimes looks weird for the uninitiated. Now this alone should lead to a "Partially redundant" message, but with more things involved it may lead to the situation you are facing.

Example: the circle is fixed in the center

Snip macro screenshot-775afa.png (3.6 KiB) Viewed 1186 times

Symmetry seems reasonable, because both points should have the same distance to the x-axis. However, as they lie on the same circle, it is sufficient to have a vertical constraint.

[jimmihenry]

I believe i understand the arc symmetry constrains, and yes left side of my picture i have some partial redundancy, on the right two solutions.
The solutions are less elegant, a distance of zero is asking for trouble? In this case a center point constrain would be nice to have. I am not
quite sure if it is the symmetry or the constraint coincident causing the redundancy. Working with a sketch of a outdated FreeCAD beta i had a
orange sketch but i can not replicate this behavior anymore, i already fixed it.


The second issue i ran into was tracing external parts

This is the silhouette i'd like to trace


In the picture below i ran into a problem. I need to place an arc. 1 is the center point, 2 and 3 is the arc itself. And bam a redundancy in
my face. This one i do not understand. But i could close the geometry, yesterday with the FreeCAD_weekly-builds-24665-Win-Conda_vc14.x-x86_64
the nose of my F22 air frame sketch disintegrated after i left the sketch. But it is all good now i guess.


The following 3 arcs gave me some more redundancy but the geometry was stable. So it is not broken with the builds-24693.
Cheers

[chrisb]

The solutions are less elegant, a distance of zero is asking for trouble?

You should avoid dimensions if you can use geometric constraints instead. I cannot see it quite clearly, but it looks as if you should use a point-on-object constraint on the x-axis.

The second issue i ran into was tracing external parts

You can upload the file for further investigation.

[jimmihenry]

Here you go my sketch for investigation. The nose of the F22 is made out of 4 arcs. I have connected one of the arcs to the external geometry.

https://www.youtube.com/watch?v=88OxpZYb7Uw&t=1s