Constraining an elliptical arc in sketcher

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CandL
Posts: 85
Joined: Thu Oct 29, 2020 6:41 pm

Constraining an elliptical arc in sketcher

Post by CandL »

Code: Select all

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.29177 (Git)
Build type: Release
Branch: releases/FreeCAD-0-20
Hash: 68e337670e227889217652ddac593c93b5e8dc94
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.2
Locale: English/United States (en_US)
Installed mods: 
  * A2plus 0.4.54b
  * BIM 2021.12.0
  * FeedsAndSpeeds 0.4.0
Sketcher module.
SketcherEllipticalArc.png
SketcherEllipticalArc.png (66.07 KiB) Viewed 607 times
Because the contraint window was not big enough.
constraint.png
constraint.png (25.77 KiB) Viewed 607 times

Trying to understand the best way to constrain the elliptical arc. I want one quarter of the arc. So the following should be true
  • The arcs endpoints are coincident with the adjoining line end points
    The major and minor axis and the center of the ellipse should be co-linear with end points
As you can see I still have one degree of freedom.

Thanks
Carl
domad
Veteran
Posts: 2053
Joined: Mon Jun 22, 2020 12:16 pm

Re: Constraining an elliptical arc in sketcher

Post by domad »

CandL wrote: Wed Jun 29, 2022 6:04 pm .......
Hello CandL, greetings to the community!

... this is what is missing
Attachments
missing constraint.gif
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CandL
Posts: 85
Joined: Thu Oct 29, 2020 6:41 pm

Re: Constraining an elliptical arc in sketcher

Post by CandL »

Thanks ... Still not sure if I am doing it right but it works.

Here are my steps. (basically breadcrumbs for the next time I need to re-learn this)

From two fully constrained lines one vertical one horizontal.

- Create the arc segment close not on the end points
- Attach one LINE endpont to the major axis via "constrain pt to an object" (closest line end point )
- Attach other LINE endpont to the minor axis via "constrain pt to an object" (closest line end point )
- Make the end pts of the arc coincident with the end points of the lines ( 2 operations)
- Make either the major or minor axis vertical or horizontal

What I like is there are no dimensions, just geometric constraints.

Thanks for the help.

Carl
domad
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Posts: 2053
Joined: Mon Jun 22, 2020 12:16 pm

Re: Constraining an elliptical arc in sketcher

Post by domad »

....
I'm glad you said:
CandL wrote: Wed Jun 29, 2022 7:26 pm ....
What I like is there are no dimensions, just geometric constraints.
it is a fundamental rule for the best creation of constraints, it is very rare to find someone who notices this at the first tests.
Very good! ;)
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Shalmeneser
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Posts: 9475
Joined: Wed Dec 23, 2020 12:04 am
Location: Fr

Re: Constraining an elliptical arc in sketcher

Post by Shalmeneser »

:idea:
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Hellipse_SHALM.FCStd
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