Steck with 2 degree of freedom, but I cannot move anything by drag

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altazar
Posts: 14
Joined: Wed May 02, 2018 9:48 am

Steck with 2 degree of freedom, but I cannot move anything by drag

Postby altazar » Wed Jan 23, 2019 1:28 pm

Hi there,

Joined you have a FreeCAD file with a Stektch which is troubling.
I cannot move anything by dragging even it is stated that there is still 2 degree of freedom.

What do you think about ?

Kind regards,
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GeneFC
Posts: 1025
Joined: Sat Mar 19, 2016 3:36 pm
Location: Punta Gorda, FL

Re: Steck with 2 degree of freedom, but I cannot move anything by drag

Postby GeneFC » Wed Jan 23, 2019 2:40 pm

Both the length of the object and the overall vertical position are not set. The object is unmovable because there are redundant constraints. Once the sketcher becomes unhappy various strange things can occur.

The Validate Sketch tool in PartDesign does not find those redundant constraints, however. I do not know why.

To complete the constraints just set a vertical distance of any vertex to the origin and set a length for the long lines.

A better approach would be to remove the tangent constraints and symmetry constraint and carefully re-apply a minimum set of constraints.

Gene
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meme2704
Posts: 2926
Joined: Sat Apr 01, 2017 2:47 pm
Location: Vosges

Re: Steck with 2 degree of freedom, but I cannot move anything by drag

Postby meme2704 » Wed Jan 23, 2019 4:33 pm

Hi
There are at least 3 errors
verticality on a point of center, radius built in 2 times, 1 point of excess between the radius and the segment of right
Erase all that, use the right constraints and it'll go
chrisb
Posts: 19042
Joined: Tue Mar 17, 2015 9:14 am

Re: Steck with 2 degree of freedom, but I cannot move anything by drag

Postby chrisb » Wed Jan 23, 2019 6:57 pm

Interesting example. Abdullah, should we create an issue?
abdullah wrote: ping
A possibility to fix this is to replace the top tangency and vertical constraint with a coincidence. Even better might be to replace the two arcs with a single one.
abdullah
Posts: 3174
Joined: Sun May 04, 2014 3:16 pm

Re: Steck with 2 degree of freedom, but I cannot move anything by drag

Postby abdullah » Thu Jan 24, 2019 12:35 pm

chrisb wrote:
Wed Jan 23, 2019 6:57 pm
Interesting example. Abdullah, should we create an issue?
abdullah wrote: ping
A possibility to fix this is to replace the top tangency and vertical constraint with a coincidence. Even better might be to replace the two arcs with a single one.
Yup. It looks like a good corner case for a GCS ticket.

Constraint10, which is a vertical alignment, appears to be the culprit. Remove this one, which is redundant (and should be reported), and then you get your 2 DoFs, the length of the vertical line and the position of the whole with respect to the origin.
chrisb
Posts: 19042
Joined: Tue Mar 17, 2015 9:14 am

Re: Steck with 2 degree of freedom, but I cannot move anything by drag

Postby chrisb » Thu Jan 24, 2019 1:57 pm

freedman
Posts: 995
Joined: Thu Mar 22, 2018 3:02 am
Location: Washington State, USA

Re: Steck with 2 degree of freedom, but I cannot move anything by drag

Postby freedman » Thu Jan 24, 2019 3:32 pm

A nice feature addition would be to add the little red exclimation error symbol next to the tool selection feature that rides next to the cursor. It's easy to miss the sketcher error when your focus is so much on the sketch. I use 2 monitors so the error pops up on the other screen.