[SOLVED] How to set tolerance on Part Cut/Fuse operations

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ceremcem
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[SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby ceremcem » Tue Sep 18, 2018 1:21 pm

With a relatively large assembly, sometimes solver does not exactly calculate the placements (I suppose), so a face is left after the Cut operation. Think that we want to subtract the red one from the big one:
1.png
1.png (9.54 KiB) Viewed 708 times
If the red shape's height is a little bit smaller than the big one (big: 10mm, small: 10mm - 0.00001mm) we still see the height of the red part as "10.00 mm" (not ~10.00 mm), and there is a little piece is left after the Cut operation:
2.png
2.png (2.54 KiB) Viewed 708 times
How can we define a tolerance so that we could remove the face for that amount of differences?
Last edited by ceremcem on Tue Sep 18, 2018 4:31 pm, edited 2 times in total.
freecad-heini-1
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Re: How to set tolerance on Part Cut/Fuse operations

Postby freecad-heini-1 » Tue Sep 18, 2018 1:28 pm

Sometimes I need to change the tolerance (accuracy) for boolean operation with imported step files.
Easiest way is to use the defeaturing workbench. There exists an easy tool to set the accuracy, lets say 0,001mm, select the solid and execute. It helped me in so many cases. Very nice.
Sometimes I used the same trick with PTC Creo.
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ceremcem
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Re: How to set tolerance on Part Cut/Fuse operations

Postby ceremcem » Tue Sep 18, 2018 4:30 pm

freecad-heini-1 wrote:
Tue Sep 18, 2018 1:28 pm
Sometimes I need to change the tolerance (accuracy) for boolean operation with imported step files.
Easiest way is to use the defeaturing workbench. There exists an easy tool to set the accuracy, lets say 0,001mm, select the solid and execute.
It was hard for me to find it at first sight, here it is (for the future readers):
defeaturing-set-tolerance.png
defeaturing-set-tolerance.png (153.17 KiB) Viewed 690 times
Thanks!
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DeepSOIC
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby DeepSOIC » Tue Sep 18, 2018 5:13 pm

There is a parametric tool in OpenSCAD workbench that increases tolerance. Since you are dealing with imported shapes, you probably don't care much about parametricity, but it may come in handy.
OpenSCAD IncreaseTolerance
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ceremcem
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby ceremcem » Tue Sep 18, 2018 6:03 pm

DeepSOIC wrote:
Tue Sep 18, 2018 5:13 pm
Since you are dealing with imported shapes
Actually I'm facing this problem with the parts I've drawn by myself. I know the lengths are equal, but their placements might not be somewhat accurate, so they are not subtracted "correctly" (as I expected)
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nemesis
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby nemesis » Tue Sep 18, 2018 9:18 pm

ceremcem wrote:
Tue Sep 18, 2018 6:03 pm
DeepSOIC wrote:
Tue Sep 18, 2018 5:13 pm
Since you are dealing with imported shapes
Actually I'm facing this problem with the parts I've drawn by myself. I know the lengths are equal, but their placements might not be somewhat accurate, so they are not subtracted "correctly" (as I expected)
I guess this is more a tangency problem than a placement issue.
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ceremcem
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby ceremcem » Wed Sep 19, 2018 9:51 am

DeepSOIC wrote:
Tue Sep 18, 2018 5:13 pm
OpenSCAD IncreaseTolerance
This tool is exactly what I wished to have. Thanks!

This tool will also help when we need an intended amount of tolerance (say 0.2mm) between parts that one will go through the other, like this.
nemesis wrote:
Tue Sep 18, 2018 9:18 pm
I guess this is more a tangency problem than a placement issue.
I'm investigating this case.
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nemesis
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby nemesis » Wed Sep 19, 2018 6:30 pm

ceremcem wrote:
Wed Sep 19, 2018 9:51 am

I'm investigating this case.
have a look here
https://www.opencascade.com/doc/occt-7. ... thms_11a_1
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ceremcem
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby ceremcem » Wed Sep 19, 2018 7:50 pm

nemesis wrote:
Wed Sep 19, 2018 6:30 pm
have a look here
https://www.opencascade.com/doc/occt-7. ... thms_11a_1
Are you saying "don't try to solve such tolerance oriented problems by trying to reduce the error, use fuzzy operators"? That would fit into my case, though.
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nemesis
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Re: [SOLVED] How to set tolerance on Part Cut/Fuse operations

Postby nemesis » Wed Sep 19, 2018 8:12 pm

ceremcem wrote:
Wed Sep 19, 2018 7:50 pm
Are you saying "don't try to solve such tolerance oriented problems by trying to reduce the error, use fuzzy operators"? That would fit into my case, though.
Well it looks like it fits your initial question about why there is a littl surface left after boolean operation.
I guess using a fuzzy option is the solution (no idea how to use it)