Can't join manifolds

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raidho36
Posts: 14
Joined: Fri May 08, 2020 3:10 pm

Can't join manifolds

Postby raidho36 » Sun Jun 07, 2020 10:52 pm

I'm trying to make a fan manifold to blow across 5 small heatsinks (3d printer cooling) but none of the methods I tried result in usable geometry. I've tried lofting solid pipes and using part thickness, that didn't work at all. I've tried lofting sketches with built-in thickness but they won't join using Connect Walled Objects function. I've tried making additive and subtractive lofts to produce walled pipes but these won't join either. I've tried making all the additive pipes and then carve them using subtractive pipes, but those wouldn't even generate the manifolds to begin with, it would fail after the first one. Finally, I've tried making lofts one per body and join them using boolean operations, but those either fail completely or produce invalid results.
Attachments
Untitled.png
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fan manifold.FCStd
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chrisb
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Re: Can't join manifolds

Postby chrisb » Mon Jun 08, 2020 1:29 am

I guess you cannot make a boolean union of these due to coplanar issues.
I would recommend to model this in one body.You can try thickness, but as that is one of the most picky tools I would not rely on it. Then you have to model the manifold a second time with slightly smaller subtractive sweeps.
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raidho36
Posts: 14
Joined: Fri May 08, 2020 3:10 pm

Re: Can't join manifolds

Postby raidho36 » Mon Jun 08, 2020 1:32 am

chrisb wrote:
Mon Jun 08, 2020 1:29 am
I would recommend to model this in one body.You can try thickness, but as that is one of the most picky tools I would not rely on it. Then you have to model the manifold a second time with slightly smaller subtractive sweeps.
Yes I tried that, it did not work. When modeling it in one body, it fails almost immediately producing the same invalid results as if I modeled them separately and used boolean union.
chrisb
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Re: Can't join manifolds

Postby chrisb » Mon Jun 08, 2020 1:34 am

raidho36 wrote:
Mon Jun 08, 2020 1:32 am
Yes I tried that, it did not work. When modeling it in one body, it fails almost immediately producing the same invalid results as if I modeled them separately and used boolean union.
Can you upload that model?
You need at least FreeCAD 0.19.23300 to edit my current sketches.
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raidho36
Posts: 14
Joined: Fri May 08, 2020 3:10 pm

Re: Can't join manifolds

Postby raidho36 » Mon Jun 08, 2020 1:35 am

chrisb wrote:
Mon Jun 08, 2020 1:34 am
Can you upload that model?
It's in the OP.
TomB19
Posts: 161
Joined: Wed May 01, 2019 4:58 am

Re: Can't join manifolds

Postby TomB19 » Mon Jun 08, 2020 3:39 am

As I understand it,you can only export the active body. You have multiple bodies so you won't be able to export a combined mesh.

I suspect that's why Chris is asking for your version with a single body.
chrisb
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Re: Can't join manifolds

Postby chrisb » Mon Jun 08, 2020 6:09 am

TomB19 wrote:
Mon Jun 08, 2020 3:39 am
As I understand it,you can only export the active body. You have multiple bodies so you won't be able to export a combined mesh.
You can select more than one body for export. What I have seen in my 3d print slicer is that they are treated like a union.
I suspect that's why Chris is asking for your version with a single body.
Correct!
You need at least FreeCAD 0.19.23300 to edit my current sketches.
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fc_tofu
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Re: Can't join manifolds

Postby fc_tofu » Mon Jun 08, 2020 8:24 am

raidho36 wrote:
Sun Jun 07, 2020 10:52 pm
Finally, I've tried making lofts one per body and join them using boolean operations, but those either fail completely or produce invalid results.
Tiny intersected details prevent boolean operation success. (red-marked) The reason is same as @chrisb called "co-planar" issue.
I tried export your model as STEP and OBJ, and tried union them in another CAD, suface modeling app, Blender, all resulted in failure.
So my feeling is that, "co-planar" and similar issues are not FreeCAD only, but related to all Boolean/CSG workflow in all 3D apps.
fsc_2020-06-08_160520b.jpg
fsc_2020-06-08_160520b.jpg (32.6 KiB) Viewed 409 times
My workaround is cut the "neck" off. Rebuild neck with loft. Then reunion them together.
fsc_2020-06-08_160748.jpg
fsc_2020-06-08_160748.jpg (22.16 KiB) Viewed 412 times
Last edited by fc_tofu on Mon Jun 08, 2020 1:32 pm, edited 5 times in total.
drmacro
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Re: Can't join manifolds

Postby drmacro » Mon Jun 08, 2020 1:04 pm

raidho36 wrote:
Sun Jun 07, 2020 10:52 pm
Just for reference:
Attachments
Exhaust-3_test.png
Exhaust-3_test.png (17.87 KiB) Viewed 419 times
Exhaust-3_test.FCStd
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chrisb
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Re: Can't join manifolds

Postby chrisb » Mon Jun 08, 2020 1:12 pm

Part Pipe connect is worth a try too.
You need at least FreeCAD 0.19.23300 to edit my current sketches.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.