Why is this sketch not fully constrained?

[glencandle]

EDIT: I updated the image to this question in a comment below, and have swapped it out here as well (sorry for any confusion!).

Just trying to understand why this sketch isn't considered fully constrained (aka blue lines):

[jhackney1972]

You forgot to attach your model, please do so.

[glencandle]

Hi John,

That's all there is to it, there is no more geometry sketched.  Just by looking at the sketch, isn't there enough information to tell if it is fully constrained or not? 

To my knowledge a fully constrained sketch should be all black lines.  I'm just confused why mine is still considered unconstrained, when as far as the math is concerned it should be (constrained).

Of course I could have the wrong concept of what constrained means.

[jhackney1972]

Well there a number of things you may or may not have done in your sketch to cause this.  I just created the same sketch without issue so all I can suggest is to attach your model to possibly find out what is different.  Your choice.

[glencandle]

Well dang, it thought it would be more obvious than that.  I was just hoping to expand my knowledge a little but I've moved on and to go back to that point would be more trouble than its worth.  Thanks though, cheers.

[jhackney1972]

I will take a guess but my guess assumes you created the polygon using the Polygon command.  If so I believe you missed the origin with the center of your polygon as I did in the attached model.  You cannot see it but it is not constrained.

Edit: No, that cannot be it, since the lower line is showing constrained.

[davebYYPCU]

If it’s blue, click drag it, should show you then and there, why more constraint is required.

Might help…..

[glencandle]

That was my first guess as well, and indeed the line was not click and draggable. 

I think it might be a matter of Fusion not keeping up with me, which I find happens a lot.  (I.e. sometimes I'll rename a sketch, but then watch as a few moments later Fusion will magically revert the sketch name back to what it was before.)  My theory is that if I saved the sketch in that state it would have become constrained once Fusion caught up with me.  

(I know it's a weird theory, and I'm sure the developers would tell me I'm crazy, but this often does happen to me.)

[FrodoLoggins]

Well that only works when one is able to move blue sketch lines.

Sometimes I'll click on a blue line to drag it and it won't move. Adding a dimension to the blue "immovable" line moves it of course but clicking/dragging won't.

[glencandle]

In lieu of all of the responses above I've decided to recreate the issue.  As you can see in the attached image all of the dimensions are constrained, but the lines are blue.  Project file attached as well.

Cheers!

[KristianLaholm]

Where does this unconstrained point that is all by itself come from?

How did you create the sketch?

[glencandle]

Hi sorry for the confusion that was the original image.  I've updated the question with a new image and a project file (in one of the comments).  Cheers.

[glencandle]

Hi John, thanks for making me think.  I've decided to recreate the issue, if you go a few comments back you'll find an updated image and project file illustrating my issue. 

[jhackney1972]

I grabbed the model from Message #10.  I then removed the cross sketch dimension and added one leg and the sketch is fully constrained.  I removed all of the Reference dimensions and  adding the one leg dimension works also.  A dimension from the bottom leg to the apex point will work as well.  Not sure why a dimension like your original will not work.

[jeff_strater · Accepted solution]

Yes, I'd say that this is a bug in the solver.  To be honest, though, this seems an unusual way to dimension a polygon.  Valid, in a mathematical sense, but just not the way I, personally, would do it.  The video below shows other ways to dimension the pentagon that do show as fully constrained.

[glencandle]

Thanks Jeff, I always appreciate learning new techniques.  Fwiw I was dimensioning this way because it is easier for me to think in terms of the longest dimension of my part's outer shape. 

There might be many ways to skin a cat, but Fusion definitely gets cranky if I think too far outside the box 😂

[FrodoLoggins]

To piggy back off my thread derailment; Any idea why it took me 3 tries (and the last try had a bit of a delay) to finally drag this blue radius?:

File attached.

[TheCADWhisperer]

@FrodoLoggins 

I would expect to see issues with sketches like this...

[FrodoLoggins]

Why?

[TheCADWhisperer]

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@FrodoLoggins wrote:

Why?

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Are you ready to learn how to use history-based parametric modeling correctly?

I don't want to waste time if you aren't ready.