Union fails

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Invictus
Posts: 2
Joined: Thu Feb 14, 2019 5:12 am

Union fails

Postby Invictus » Thu Feb 14, 2019 5:26 am

Hi,

I'm trying to create a transition from a rectangle to a circle. I lofted 4 solids from each corner of the rectangle to the circle, and began to make unions of the solids, but the last solid could not be added to the union. Instead, it appears to give me the difference of the solids. What am I doing wrong? Could someone please help? Thanks.
Solids.png
Before union
Solids.png (73.13 KiB) Viewed 109 times
Union.png
After union
Union.png (17.06 KiB) Viewed 109 times

OS: Windows 7
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13522 (Git)
Build type: Release
Branch: releases/FreeCAD-0-17
Hash: 3bb5ff4e70c0c526f2d9dd69b1004155b2f527f2
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: English/UnitedKingdom (en_GB)
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Flue5.FCStd
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microelly2
Posts: 4155
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Re: Union fails

Postby microelly2 » Thu Feb 14, 2019 7:08 am

Sometimes it helps to move one object a little bit (micrometer).
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easyw-fc
Posts: 2209
Joined: Thu Jul 09, 2015 9:34 am

Re: Union fails

Postby easyw-fc » Thu Feb 14, 2019 8:39 am

I made a boolean fragment and then created a solid from external faces
solid.PNG
solid.PNG (215.36 KiB) Viewed 98 times
Flue5-solid.FCStd
(163.14 KiB) Downloaded 2 times
Invictus
Posts: 2
Joined: Thu Feb 14, 2019 5:12 am

Re: Union fails

Postby Invictus » Thu Feb 14, 2019 2:15 pm

Thanks, easyw-fc it worked!
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NormandC
Posts: 17779
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Location: Québec, Canada

Re: Union fails

Postby NormandC » Sat Feb 16, 2019 7:32 am

easyw-fc wrote:
Thu Feb 14, 2019 8:39 am
I made a boolean fragment and then created a solid from external faces
Unfortunately, the end shape is no longer parametric.

Invictus wrote:
Thu Feb 14, 2019 5:26 am
I lofted 4 solids from each corner of the rectangle to the circle
There's a much more efficient method: create only one Loft, and use Part Mirror to mirror it on two planes.

Invictus wrote:
Thu Feb 14, 2019 5:26 am
Instead, it appears to give me the difference of the solids. What am I doing wrong?
It's not the difference between the solids, the operation fails and produces only some of the faces. The problem is that the OCC kernel struggles to handle tangency between solids in Boolean operations. The lofts all end up with the same circular section at the top, causing tangency. The trick is to remove the tangency condition, which is easy here: make a single loft, and cut it along the XZ and YZ planes to keep only a 1/4 of it.

Boolean operations sometimes have trouble with solids that have co-planar faces, but they don't struggle as much as with tangency.

FC_Invictus_Flue5_01.png
FC_Invictus_Flue5_01.png (9.09 KiB) Viewed 27 times

Then mirror it, fuse it with the loft; mirror the fusion, and fuse again.

FC_Invictus_Flue5_02.png
FC_Invictus_Flue5_02.png (24.08 KiB) Viewed 27 times

Finally, set the Fusion001's Refine property to true to get rid of the residual edges on the top planar face.

FC_Invictus_Flue5_03.png
FC_Invictus_Flue5_03.png (22.6 KiB) Viewed 27 times

This results in a fully parametric model.
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meme2704
Posts: 2367
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Location: Vosges

Re: Union fails

Postby meme2704 » Sat Feb 16, 2019 8:45 am

My solution
Attachments
couronne du roi des fous.PNG
couronne du roi des fous.PNG (42.13 KiB) Viewed 16 times
couronne du roi des fous.FCStd
(211.86 KiB) Not downloaded yet