Symetric Constraint in Sketch

[Lonnie.Cady]

I have a sketch that is a rectangle with rounded corners.  I projected the construction axis into the sketch and constrained the sides symetric to the projected construction axis.  I can stll move the sketch.  Shouldn't the sektch maintain the symetric constraint??

 

[innovatenate]

This doesn't look right to me. When you hover over the symmetric constraint with your mouse, which sketch entities are highlighted? Perhaps, a wrong selection has been made or the entities have resolved to an unintended entity when the sketch was modified....

Would you be able to share the file? Feel free to e-mail it to me directly if you would prefer (nathan.chandler@autodesk.com). 

You may also consider using points and midpoints to create relationships that will have the same effect as a symmetric constraint. In the below video, I show another user how to make the sketch symmetric about the vertical axis utilizing midpoint constraint.

 I hope that helps. Please let me know if you have any questions.

Thanks,

[innovatenate]

The issue appears to be a conflict between the sketch dimension and the symmetric constraint. If you edit the sketch dimension (value 65.3 mm), the symmetric constraint will be maintained. If you delete that dimension and then drag the sketch entities, there is no problem. However, if you leave that dimension and then drag, the solver does not behave how I would expect it to. I will forward this incident to development for further investigation. 

Thank you for reporting this. 

Kind Regards,

[Lonnie.Cady]

Thank you very much.  To add a little more to this, one other issue is that I create the rectangle as a center ponit rectange and was going to constrain the center of the rectangle to the origin.  I then added sketch fillets and the center construction lines that for the x are no longer attached.

[innovatenate]

I am able to follow along with this one.. I note that the dimensions are no longer associated with the size of rectangle and the reference lines do not seem to have any impact on the position of the rectangle. However by adding the fillets, the coincident constraints are removed between the endpoints of the lines of the rectangle and of the reference lines. The glue holding everything together has been removed!

This may be plus one for the work-around I mentioned before, utilizing midpoints and horizontal or vertical constraints to center a rectangle (provided that the fillets are have the same radii).  I understand why this behavior happens, but the question is how would you like to see it behave? I'd recommend adding an enhancement to the Fusion 360 IdeaStation for this issue.

http://forums.autodesk.com/t5/fusion-360-ideastation-request-a/idb-p/125

If you get a chance, post a link back here and I will vote it up!

Thanks,

[Lonnie.Cady]

Thanks, I am not sure how it should be handled.  Mayby me understanding it better is all that is required.

I will test in my other modeling software in the morning.  But I am thinking it maintains the constraint to the virtual sharp not the endpoint of the lines.

[Lonnie.Cady]

I have tested in another cad system I am familiar with and the endpoints of the construction lines of  a center point rectangle are constrained to the intersection of the the 2 rectangle edges.  So when the fillets are added the the constraint relationship is maintained.