Can't pad a sketch based on external geometry

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NewJoker
Posts: 13
Joined: Sun Oct 11, 2020 7:49 pm

Can't pad a sketch based on external geometry

Postby NewJoker » Wed May 12, 2021 4:55 pm

Hi,

I am testing the "External Geometry" tool. I started from creating this simple part and offsetting a plane from its face:

part.JPG
part.JPG (27.52 KiB) Viewed 370 times

Then I created a sketch on this plane and used the "External Geometry" tool to project the edges of the previously created part on the new sketch:

sketch.JPG
sketch.JPG (40.85 KiB) Viewed 370 times

Finally, I outlined the projected contour with line tool. Now the problem is that I can't use Pad tool on this new sketch:

sketch 2.JPG
sketch 2.JPG (33.86 KiB) Viewed 370 times

What's going on here ? Am I doing something wrong ?

Thanks in advance for your help.
drmacro
Posts: 3402
Joined: Sun Mar 02, 2014 4:35 pm

Re: Can't pad a sketch based on external geometry

Postby drmacro » Wed May 12, 2021 5:09 pm

See if this example helps.

The Datum plane is not needed. Also, it is recommended to avoid attaching sketches to generated geometry because of the topological naming problem.

https://wiki.freecadweb.org/Topological_naming_problem
https://wiki.freecadweb.org/Feature_edi ... ble_models
https://wiki.freecadweb.org/Basic_Attachment_Tutorial
Snip macro screenshot-4a458d.png
Snip macro screenshot-4a458d.png (178.89 KiB) Viewed 360 times
Attachments
PadExample.FCStd
(25.15 KiB) Downloaded 4 times
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NewJoker
Posts: 13
Joined: Sun Oct 11, 2020 7:49 pm

Re: Can't pad a sketch based on external geometry

Postby NewJoker » Wed May 12, 2021 5:15 pm

Thank you very much. However, I actually planned to extrude it in the opposite direction (so that a new solid, separated from the original one by a gap, will be created) and that's why I use plane with offset. Is it possible to do it the way I wanted ?

I also tried deleting those lines created with External Geometry tool to avoid dependencies but it didn't help.
Bance
Posts: 1958
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Can't pad a sketch based on external geometry

Postby Bance » Wed May 12, 2021 5:36 pm

NewJoker wrote: Wed May 12, 2021 5:15 pm Is it possible to do it the way I wanted ?
No, there is a single solid rule for bodies.

You must instead use a shape binder in a new body.(there are other methods including carbon copy!) :D
NewJoker
Posts: 13
Joined: Sun Oct 11, 2020 7:49 pm

Re: Can't pad a sketch based on external geometry

Postby NewJoker » Wed May 12, 2021 5:47 pm

Bance wrote: Wed May 12, 2021 5:36 pm
No, there is a single solid rule for bodies.

You must instead use a shape binder in a new body.(there are other methods including carbon copy!) :D
That's what I also tried - creating a new body and moving the second sketch to it. But I couldn't do it this way. ShapeBinder might be a good option but for it to work the target body must already exist, right ?
Last edited by NewJoker on Wed May 12, 2021 6:16 pm, edited 1 time in total.
Bance
Posts: 1958
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Can't pad a sketch based on external geometry

Postby Bance » Wed May 12, 2021 6:02 pm

Yes, Carbon copy might be good here.

Create a new body and sketch, select CC tool, press CTRL ALT and select original sketch. ( better if pad is invisible at this time)
NewJoker
Posts: 13
Joined: Sun Oct 11, 2020 7:49 pm

Re: Can't pad a sketch based on external geometry

Postby NewJoker » Wed May 12, 2021 6:26 pm

Thanks, CarbonCopy tool works fine in this case:

body.JPG
body.JPG (58.37 KiB) Viewed 297 times

But I still wonder if it's possible to achieve the same effect using External Geometry tool.
Bance
Posts: 1958
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Can't pad a sketch based on external geometry

Postby Bance » Wed May 12, 2021 6:44 pm

No not between bodies, you need to import geometry with a shape-binder then use ext geom.

Anyway it is much better not to reference solid (generated) geometry at all.

See Topological naming problem.
NewJoker
Posts: 13
Joined: Sun Oct 11, 2020 7:49 pm

Re: Can't pad a sketch based on external geometry

Postby NewJoker » Wed May 12, 2021 7:03 pm

Great, this works as well:

part 2.JPG
part 2.JPG (50.04 KiB) Viewed 282 times

In this case it's also necessary to hide the original pad.

Again, thank you guys for help.
chrisb
Posts: 35340
Joined: Tue Mar 17, 2015 9:14 am

Re: Can't pad a sketch based on external geometry

Postby chrisb » Wed May 12, 2021 8:18 pm

If both parts are equal you should consider to use a clone, or if you can arrange them appropriately, a mirror.
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