Intersecting contours pocket.

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kisolre
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Joined: Wed Nov 21, 2018 1:13 pm

Intersecting contours pocket.

Postby kisolre » Thu Jul 04, 2019 7:07 am

I was under impression that intersecting contours in a single sketch was not good. Why does the following groove work?
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IntContGroove.JPG
IntContGroove.JPG (41.78 KiB) Viewed 229 times
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Trying to pocket with the same sketch fails (multiple solids) or gives wrong faces depending on there I move the circles up/down (still intersecting).

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chrisb
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Re: Intersecting contours pocket.

Postby chrisb » Thu Jul 04, 2019 7:17 am

Can you upload the file?
kisolre
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Re: Intersecting contours pocket.

Postby kisolre » Thu Jul 04, 2019 9:47 am

Sure. But I thought it was clear from the screenshot... Those circles are in one sketch and grove works perfectly fine. First they were just touching - no problem there. Then I moved them closer togerher and realized that they were intersecting and would probably make just the outer contour from arcs. But got lazy and decided to give it a go. And strangely it worked ?!?
Attachments
Crutch handle.FCStd
(516.64 KiB) Downloaded 7 times
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papyblaise
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Re: Intersecting contours pocket.

Postby papyblaise » Thu Jul 04, 2019 1:03 pm

Hello
So resolu or not :?:
chrisb
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Re: Intersecting contours pocket.

Postby chrisb » Thu Jul 04, 2019 1:13 pm

kisolre wrote:
Thu Jul 04, 2019 9:47 am
Sure. But I thought it was clear from the screenshot... Those circles are in one sketch and grove works perfectly fine. First they were just touching - no problem there. Then I moved them closer togerher and realized that they were intersecting and would probably make just the outer contour from arcs. But got lazy and decided to give it a go. And strangely it worked ?!?
It was clear from the image, but rebuilding with eventually occurring boundary conditions takes some time; so I prefer to use your file. I will fiddle later with it.
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quick61
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Re: Intersecting contours pocket.

Postby quick61 » Thu Jul 04, 2019 2:03 pm

kisolre wrote:
Thu Jul 04, 2019 9:47 am
Sure. But I thought it was clear from the screenshot... Those circles are in one sketch and grove works perfectly fine. First they were just touching - no problem there. Then I moved them closer togerher and realized that they were intersecting and would probably make just the outer contour from arcs. But got lazy and decided to give it a go. And strangely it worked ?!?
Actually it didn't work. Yes, it "looks" like it did, but run a geometry check, BOP check enabled and the errors show up. Are you "getting away with" it at this point? Probably. Is it a good model? No.

Use the Arcs, and everything checks fine.

Mark
This post made with 0.0% Micro$oft products - GOT LINUX?
kisolre
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Re: Intersecting contours pocket.

Postby kisolre » Thu Jul 04, 2019 5:55 pm

quick61 wrote:
Thu Jul 04, 2019 2:03 pm
Actually it didn't work.
The solid that does not pass BOP check is the fillet. Groove passes Ok. I tried groove with arcs and fillet fails again but groove is Ok. Any idea what "BOPAlgo GeomAbs_C0" means?
Attachments
GroveWithArcs.JPG
GroveWithArcs.JPG (40.94 KiB) Viewed 156 times
TheMarkster
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Re: Intersecting contours pocket.

Postby TheMarkster » Fri Jul 05, 2019 3:23 am

It's curious that it works with revolve/groove. Maybe that algorithm is more robust than Pad/Pocket.
TheMarkster
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Re: Intersecting contours pocket.

Postby TheMarkster » Fri Jul 05, 2019 5:06 am

kisolre wrote:
Thu Jul 04, 2019 5:55 pm
The solid that does not pass BOP check is the fillet. Groove passes Ok. I tried groove with arcs and fillet fails again but groove is Ok. Any idea what "BOPAlgo GeomAbs_C0" means?
https://people.cs.clemson.edu/~dhouse/c ... plines.pdf

Page 92 seems to explain it. It has something to do with how the curves join.
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Chris_G
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Re: Intersecting contours pocket.

Postby Chris_G » Fri Jul 05, 2019 3:22 pm

kisolre wrote:
Thu Jul 04, 2019 5:55 pm
The solid that does not pass BOP check is the fillet. Groove passes Ok. I tried groove with arcs and fillet fails again but groove is Ok. Any idea what "BOPAlgo GeomAbs_C0" means?
From what I understand of BOP Check, it does 2 different things :
- it checks actual errors in a shape
- it also tries to highlight the properties of a shape that could lead to errors if this shape is used in a boolean operation

BSpline curves can have sharp points (and surfaces can have sharp edges) : this is C0 continuity.
( I don't know if other geometries can have C0 continuity ).
I think this C0 Continuity is reported in BOP Check because it is a potential failure condition for some higher level operations.
For example, surface offsetting doesn't work on C0 continuous surfaces.
I think sweeping along a C0 curve can also produce twist.

Attached file is a sketch, that has been approximated to a single BSpline curve (with a sharp 'C0' point), that has been extruded to a face (with a sharp 'C0' edge).
This curve and this surface are perfectly valid, but they may probably make some boolean operations to fail.
Attachments
C0_Face.FCStd
(7.23 KiB) Downloaded 3 times