Cannot fully constrain sketch

[mattmyer6E696]

I am attempting to create a sketch section using a half ellipse

Once i trim away the unwanted half of the ellipse, I cannot fully constrain the sketch. Tried everything but the half ellipse stays blue (unconstrained) 

(see attached screenshot)

[jeff_strater]

can you shared this sketch here?  I know that there are issues with trimmed ellipses in general, and particularly with the fully-constrained analysis.  It may be that, or some constraint may have gotten dropped when you did the trim.  Thanks.

[mattmyer6E696]

Hi Jeff

I couldn't resolve it so I used conic arcs with the rho parameter set to 0.414 to simulate an ellipse profile and this worked fine. I'm used to working in PTC Creo where everything has to be correctly constrained. 

[jeff_strater]

You don't have to fully constrain sketches in Fusion.  It's a good idea, certainly, but the main reason for that is for stability under edit.  If you are reasonably convinced that the sketch is fully constrained, it just doesn't show up with black lines and and the lock icon, you can proceed.  And again, if you want to share the design, we can take a look at it.  Thanks,

[TheCADWhisperer]

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@jeff_strater wrote:

 If you are reasonably convinced that the sketch is fully constrained, it just doesn't show up with black lines and and the lock icon, you can proceed.  And again, if you want to share the design, we can take a look at it.  Thanks,

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I quite frequently have fully defined ellipse that does not show as black or lock icon.

In the Attached I attempted to reproduce the OP issue from Canvass image without even trimming the ellipse (I normally try to avoid trimming ellipse because then they almost always show blue when fully defined).

[mattmyer6E696 · Accepted solution]

This is an example of the type of sketch I'm trying to constrain

It's a section through a guitar neck. When you trim the ellipse, it becomes impossible to fully constrain it.

[jeff_strater · Accepted solution]

thanks, we will look at that case, thanks for sharing it.  The other option is to not trim the ellipse.  Fusion is fine with untrimmed geometry - you don't need to trim it, and can select whatever profile subset you want.  Or, just don't worry about it not being fully constrained.  It's not critical in Fusion, you can still continue with your design.

[jeff_strater]

created bug FUS-95467 to track this issue.

[rrodriguezF5XQ6]

Gents,   I was able to make the arc black by right click and select fixed, turning the arc green.  Then unfixing the arc and it turned black and stayed black.

If anyone has tried this let me know if you experience the same.

Robert

[rrodriguezF5XQ6]

Try fixing the arc and unfixing the arc to see if it displays as fully constrained.

Regards

Robert

[g-andresen]

Hi,

Construction lines must also be defined.

günther