Union of three bodies fails

[JiPe38]

Hi everyone
I tried to make an union of three bodies. One central is a clone of a model cube, the two others are clones of a model half cylindre.
I create my three clones, add a translation on x on the first half cylindre, a rotation around y and an opposed translation on x on the second half cylindre. I see correctly my three bodies, joined in the final position that I want. I then ask the creation of a new body, with a boolean union function, select the three clones... up to there everything is smooth and OK. Then I click on the "OK" button of the boolean union and, upon it's exit, I see only the last two selected bodies of the union.
Do I miss something, or is there a known problem in such an operation ?

threeBodyUnion.FCStd

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OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.19311 (Git)
Build type: Release
Branch: master
Hash: 120b69c74f7dac8c4fa6dbc0a7e10674bde9216c
Python version: 3.7.3
Qt version: 5.12.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: French/France (fr_FR)

[chrisb]

A boolean in a PartDesign body is different from a boolean in Part: Like all other features it adds/subtracts from the solid created so far. As you don't have a solid if the boolean is the first item in the body, fancy things can happen.
PartDesign Booleans are not really a replacement for Part Booleans. If you want those, take them from Part workbench.

In your case you should simply model it all in one body.

[openBrain]

IIRC it has already been reported that Union bugs with 3 objects. I'll try to find a link.

[JiPe38]

A boolean in a PartDesign body is different from a boolean in Part: Like all other features it adds/subtracts from the solid created so far. As you don't have a solid if the boolean is the first item in the body, fancy things can happen.
PartDesign Booleans are not really a replacement for Part Booleans. If you want those, take them from Part workbench.

In your case you should simply model it all in one body.

What I present in this simple example is a simplification of a complex model, reduced to show where the problem arises. I can't design this in just one body.

[chrisb]

What I present in this simple example is a simplification of a complex model, reduced to show where the problem arises. I can't design this in just one body.

But you can always use bodies which do not start with a boolean.

[openBrain]

Was in your mother language JiPe38 : https://forum.freecadweb.org/viewtopic. ... 20#p358024
But I guess this deserves a dedicated discussion. So let's go for it. I'll confirm later when I have a PC if nobody did in between.
A minimalist example would also be welcome.

[Roy_043]

This discussion?:
https://forum.freecadweb.org/viewtopic.php?f=8&t=41910

[openBrain]

This discussion?:
https://forum.freecadweb.org/viewtopic.php?f=8&t=41910

Not a lot to do with current discussion. The one you pointed talks about boolean operations of PartDesign.

[chrisb]

The one you pointed talks about boolean operations of PartDesign.

That's exactly what OP talks about:

I then ask the creation of a new body, with a boolean union function,

[Vincent B]

with partdesign the worflow is different of part.
active one body, then call the boolean feature then select the other bodies.
theses two bodies will embedded inside the first one.