Unexpected behaviour of boolean cut with clones in part design

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Joined: Thu Sep 24, 2015 3:14 pm

Unexpected behaviour of boolean cut with clones in part design

Postby brjhaverkamp » Thu Oct 17, 2019 3:43 pm

Hello all,

I was working on a part design project of our attic renovation. I used the arch workbench for the architectural view, but now I needed some structural details that I thought were easier with part design. I am still amazed at the quality of the part design toolbox these days. No hickup, and rock solid! Compliments all around here!

However, I ran into some unexpected behavior that I wanted to report/discuss, as I am not sure if it is indeed a bug or a feature:

I created the structure of the roof and put roof-elements on it of the size and shape of kingspan unidek panels.
For this I created one original element and then placed clones side by side to fill the roof on the west and south side

In the corners I need to cut of the excess material, so I created a body to cut with.
But when I cut the individual clones, the cutting shape is displaced (or the clone is cut at the place where the original resides.) Either way, the displacement of the clone wrt its original base body is not taken into account correctly, it seems.

An other slight annoyance is that the cutting body is not visible anymore after it has been used once for the first boolean. So you can not select it anymore in the 3-d view to create the next boolean cut. I found the way to reuse it by first making the body to cut active, then selecting the cutting body in the tree-view and then clicking the boolean icon in the toolbar. So it only a slight annoyance, but perhaps solvable nonetheless:-)

I have attached the file with the example. Hope it is clear. I am trying to cut "Body dakplaat west 1" (and #2,#3) with "Body dakplaat afsnijblok zuid"
#1 is cut correctly, but #2 and #3 are cut too low, or in exacly the same place as #1. (and #1 happens to sit in the same location as the original)

Before sending this to a bug report, I wanted to check here if my observation is correct.

Kind regards,


OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16117 (Git)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: dbb4cc6415bac848a294f03b80f65e888d531742
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)
3D Zolder details v7 boolean cut error.FCStd
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Joined: Tue Mar 17, 2015 9:14 am

Re: Unexpected behaviour of boolean cut with clones in part design

Postby chrisb » Thu Oct 17, 2019 5:06 pm

Sorry for prposiing something different, but I'm not able to explain the issue you face very well. I think the seemingly "moving" body is not a bug, it is because in the PartDesign Boolean the Body behaves similar to a ShapeBinder with TraceSupport=False, while you expect similar behaviour to TraceSupport=True.

I would recommend to use for this the Part workbench on the whole bodies. You can easily make the cut components visible under the boolean cut and reuse them in another cut. If it suits your modelling better you could even use a boolean common, which is not available in PartDesign yet.