partial redundant constrain issue

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jaessa
Posts: 7
Joined: Mon Aug 08, 2022 3:40 am

partial redundant constrain issue

Post by jaessa »

I am trying to create a 4 parts circle with a diameter 80. I needed the curve bench so I installed it, but after the reboot, I am not able to constrain the 4 parts. I either have partial constrain or redundant constrain. the file is attached. Any thoughts?

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: 
  * Assembly4 0.12.3
  * CurvedShapes 1.0.4
  * Silk 1.0.0
Attachments
4 parts Circle.FCStd
(6.17 KiB) Downloaded 19 times
chrisb
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Posts: 53925
Joined: Tue Mar 17, 2015 9:14 am

Re: partial redundant constrain issue

Post by chrisb »

You may have a look in one of the documents in my footer. I may later have time to fix your model. The idea is to use rather tangency and equality rather than coincidence. If you use three coincidences on the ends and center of an arc, they consume 6 degrees of freedom (DOF) while an arc has only 5.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
chrisb
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Posts: 53925
Joined: Tue Mar 17, 2015 9:14 am

Re: partial redundant constrain issue

Post by chrisb »

Here is the fixed circle as described above.
Attachments
4partsCircle_cb.FCStd
(5.37 KiB) Downloaded 18 times
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
FCuser2019
Posts: 125
Joined: Fri Sep 13, 2019 12:15 pm

Re: partial redundant constrain issue

Post by FCuser2019 »

Hello, another possible solution:
Attachments
4partsCircle_FCu2019.FCStd
(6.21 KiB) Downloaded 20 times
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Shalmeneser
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Posts: 9475
Joined: Wed Dec 23, 2020 12:04 am
Location: Fr

Re: partial redundant constrain issue

Post by Shalmeneser »

Sketcher_CreateArc (=5dof) : It's a usual problem of not overconstraining

* Arc #1 : Center + Axis + Axis (+ Radius)
* Arc #2 to #4 : Center (2dof) + Edge (2dof) + Axis (2dof)

or
* Arc #1 : Center + Axis + Axis (+ Radius)
* Arc #2 to #3 : Center + Edge + Axis
* Arc #4 : Center (2dof) + Edge (2dof) + near the 1st edge -> Horizontal or Vertical constraint (1dof) between first and last edge
jaessa
Posts: 7
Joined: Mon Aug 08, 2022 3:40 am

Re: partial redundant constrain issue

Post by jaessa »

chrisb wrote: Wed Aug 10, 2022 7:55 am You may have a look in one of the documents in my footer. I may later have time to fix your model. The idea is to use rather tangency and equality rather than coincidence. If you use three coincidences on the ends and center of an arc, they consume 6 degrees of freedom (DOF) while an arc has only 5.

I actually followed your advise and sure enough, I got fully constrained. I was following a video and that is what he did. Thanks for the explanation.
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