How to duplicate B-spline?

[mdesign]

How to duplicate B-spline (or copy and paste to have two same B-splines)?

I would like to offset that spline. So, I`ve thought that I will duplicate it and set it as parallel. I would like to get thickness to that B-spline to revolve it after.

[Shalmeneser]

Sketcher_Copy or Sketcher_Clone.

[edwilliams16]

Offsetting and duplicate+translate are different operations. The former you can only do approximately. It is particularly problematical if the inner radius of curvature is less than the offset. https://forum.freecadweb.org/viewtopic.php?t=53712

[mdesign]

Thanks a lot for your help. Is there any future plans about adding an offset tool in sketcher (even not exact).
The Interior curve after offset should have a radius minus the thickness value and position offset as shown in your link above.

edit: OK. I`ve found a sweep trick to do offset of the curve. Maybe it will be enough.

[chrisb]

I just tried the following with success:
- make an offset2D of the spline
- close the ends in Draft workbench with straight lines
- upgrade
- revolve
As upgrade is non parametric the whole process is non parametric.

[chrisb]

I would like to get thickness to that B-spline to revolve it after.

If I use a compound instead of upgrade, the model stays partially parametric. Only the Draft lines have to be corrected if the endpoints of the B-spline move. You could probably improve parametricity if you use additional sketches for the closing lines.

[mdesign]

@chrisb:

Thanks a lot. Very interesting.

After small tweaking of middle control points, the whole setup is broken. Why?

Another thing is that the final revolve is not updating after the control point move.

I like that procedural approach very much but it works strange for me. IMO that procedural offset line is flipped to the other side because those small lines are in the wrong place now. Maybe that`s why it`s not updating. But why it`s flipping after the control point moving?

Zrzut ekranu 2021-06-26 074933.jpg (129.14 KiB) Viewed 1579 times

[heda]

if you are ok with 3d-offset in part wb...

Snip macro screenshot-fde6fb.png (25.17 KiB) Viewed 1552 times

[Vincent B]

Only the Draft lines have to be corrected if the endpoints of the B-spline move. You could probably improve parametricity if you use additional sketches for the closing lines.

You can find parametric line feature in CurvesWb. Just select two vertexes in 3D view then run the tool.

[mdesign]

@GlouGlou: Thanks a lot.