Part Workbench Boolean Operations

[sharpener]

Hi,

from time to time I encountered the Boolean Operations in Part Workbench don't work at all or produce unexpected results. In the last case I tried several workarounds (searching the discussions, videos, tutorials, etc), but still no success.

What I want to do:
- have a plain cylinder
- make two sets of shallow grooves to that cylinder's surface (mutually intersecting)

What I have done:
- create a cylinder
- create a sketch
- bend the sketch around the cylinder (some macro downloaded)
- extrude the sketch
- make polar array of given extrusions (lot of variations performed here to get single solid to make the Boolean happy)
- subtract this array from the cylinder
- create mirrored sketch, repeat all the (sketch-following) steps once more

What I have received:
- the first subtraction worked more or less in all conditions
- second subtraction failed everytime

Is there any way, how to do it properly?
Thank you.

Using latest 0.19 build (21514), Win64.

2020-06-28 13_05_48-FreeCAD 0.19.png (330.54 KiB) Viewed 1596 times

[papyblaise]

please send your file

[kisolre]

Hello and welcome to the forum
Latest is 21775

If you provide your file more meaningful help will be given. For now I would suggest make the second set of cuts slightly deeper to avoid coplanar issues.
Check this thread for something similar https://forum.freecadweb.org/viewtopic.php?f=31&t=46525

[sharpener]

Right, my fault, by "latest" I meant rather "nightly builds" or whatever the git binaries are marked as. I would post the file, but it's over 1M. So I'd try to sort it out.

@kisolre, this seems promising, in general the same stuff I need. Just different parametrization. Going to check it in detail.

[sharpener]

I have tried to make the second cut deeper. After several hours of computing, it still failed.

Code: Select all

3.54e-07 <App> Document.cpp(3732): Failed to recompute wrap_sketch#Cut001: Boolean operation failed
Cut is not a solid
RL is not a solid
Recompute failed! Please check report view.
80545.7 <App> Document.cpp(3732): Failed to recompute wrap_sketch#Cut002: Boolean operation failed
Cut001 is not a solid
RL001 is not a solid
Recompute failed! Please check report view.
657256 <App> Document.cpp(3732): Failed to recompute wrap_sketch#Cut002: Boolean operation failed
Cut is not a solid
RL is not a solid
Recompute failed! Please check report view.

[sharpener]

Hopefully this might be used to download the design:
https://www.dropbox.com/s/x861sfuyyhkzx ... fcstd?dl=0

Tried to use the Part Design Workbench there, which is much more confusing now, but it seems like everything killing the Part Workbench also kills the Part Design one.

[chrisb]

This seems to be a typical coplanar issue as we have seen it here with double helices. You should make one of the patterns cut a tiny little bit deeper than the other.
BTW: Why didn't you use a helix?

[fc_tofu]

Though "co-planar" is named by plane. It actually includes various cases, co-plane, co-tangent-face, co-edge, co-tangent-edge, co-vertex.
To be specific, your case is a "co-tangent-face" issue, 2 helix grooves intersect at tangent faces.

In some cases, co-planar Boolean break model at one, such as your case.
In other cases, co-planar Boolean result in a defected shape, where tiny edges, selft-intersected edges, overlapped faces are hiden. These defects might break model in following operations.