Why 3D offset cannot be applied on a Ruled surface?

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emills2
Posts: 875
Joined: Tue Apr 28, 2015 11:23 pm

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by emills2 »

Before getting too deep in the correct way to rotate multiple copies to achieve a good seam, it is important to note the shell i made from the 2 half leaflets, even though it IS a shell, does NOT perform well with 3D offset.

even leaving aside the issue of matching rotated copies.

this probably brings us back to GLouglou's detective work about the crazy number of Poles
aorticValveAndRoot-cannot 3D offset.png
aorticValveAndRoot-cannot 3D offset.png (272.98 KiB) Viewed 1154 times
note that this time, we get a very different message: no complaints about not being a shell, just a failure to execute the 3D offset
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Vincent B
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Location: La Rochelle, France

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by Vincent B »

Most of the time, offset3D is not able to handle:
- surfaces with not continuity and thickness mismatched
- mixed surfaces (inside/outsides mixed)
- self intersection filling
- surface with BOP errors
...
amuzeshi
Posts: 13
Joined: Tue Jan 14, 2020 7:08 pm

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by amuzeshi »

emills2 wrote: Thu Jul 29, 2021 12:19 am Before getting too deep in the correct way to rotate multiple copies to achieve a good seam, it is important to note the shell i made from the 2 half leaflets, even though it IS a shell, does NOT perform well with 3D offset.

even leaving aside the issue of matching rotated copies.

this probably brings us back to GLouglou's detective work about the crazy number of Poles

aorticValveAndRoot-cannot 3D offset.png

note that this time, we get a very different message: no complaints about not being a shell, just a failure to execute the 3D offset
Thank you so much for your digging into the topic.
Today, I'll try to re-build the geometry to see whether offset eventually works ;)
emills2
Posts: 875
Joined: Tue Apr 28, 2015 11:23 pm

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by emills2 »

fyi, i'm working on an alternative (for my own sake), that you might be interested in.

the method produces a valid solid, but thickness and 3D offset are still being a royal pain (even with surfaces that are proven to be good shell/solid/boolean)

here is the basic shape, note that my design tree is pretty short compared to yours
aorticValveAndRoot_Silk01.png
aorticValveAndRoot_Silk01.png (86.66 KiB) Viewed 956 times
and this is a real solid that handles booleans

aorticValveAndRoot_Silk02.png
aorticValveAndRoot_Silk02.png (77.37 KiB) Viewed 956 times
amuzeshi
Posts: 13
Joined: Tue Jan 14, 2020 7:08 pm

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by amuzeshi »

emills2 wrote: Mon Aug 02, 2021 11:33 pm fyi, i'm working on an alternative (for my own sake), that you might be interested in...
Great!
You mean it is not worth for me to bother myself rebuilding the geometry ... ?
emills2
Posts: 875
Joined: Tue Apr 28, 2015 11:23 pm

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by emills2 »

If you're interested in my method, then i would say no, don't bother rebuilding the geometry.

in the technique i propose, all the geometry is defined in 5 sketches (white lines and circles in picture below), and these sketches produce a "half" leaflet. This is done with an external workbench that you can download directly from FreeCAD.

After that it's 1 Part>Mirror, a bunch of rotated Draft>Clone, then i use Part>shape builder to cap both ends, then shell, then solid.

Keep in mind that the original surface is fully parametric and the sketches can be edited to control the surface, but part mirror and everything else is not parametric (will not update to subsequent edits of the surface). It's really not that bad to redo all the part stuff once you get the hang of shape builder, but it's important to be aware of the pitfall.
aorticValveAndRoot_Silk03.png
aorticValveAndRoot_Silk03.png (158.38 KiB) Viewed 883 times
the best way to get proper thickness control is to define the inner surface the same way you define the outer surface, i.e. sketches then surface (not offset 3D, too unreliable).

The real benefit is that everything important is in sketches, where it can be properly dimensioned. This could be pretty important if this is in fact a medical device as its name would indicate.
aorticValveAndRoot_Silk04.png
aorticValveAndRoot_Silk04.png (147.1 KiB) Viewed 883 times
aorticValveAndRoot_Silk05.png
aorticValveAndRoot_Silk05.png (85.72 KiB) Viewed 883 times
emills2
Posts: 875
Joined: Tue Apr 28, 2015 11:23 pm

Re: Why 3D offset cannot be applied on a Ruled surface?

Post by emills2 »

amuzeshi wrote: Tue Aug 03, 2021 11:53 am Great!
You mean it is not worth for me to bother myself rebuilding the geometry ... ?
here is my file, requires addon workbench Silk.

See post above as well for general info. If you want to learn this method, send me a pm.
Attachments
aorticValveAndRoot_Silk.FCStd
(71.8 KiB) Downloaded 27 times
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