Can't find missing dimensions / constraints when using Split tool

[wfp21]

Anyone know where the missing two constraints are? I can seem to add anymore tangential constraints.

(Part attached)

[SBix26 · Accepted solution]

I think Inventor is wrong.  There are no degrees of freedom in this sketch, so it is fully constrained.

Can you satisfy my curiosity?  Why do you need to split the ellipse into six segments?

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Sam B

Inventor Pro 2022.2.1 | Windows 10 Home 21H2

[wfp21]

That's a comforting thought - I am right and Inventor is wrong.

I am approximating the head to an eclipse. Perhaps I could have used several 3 point arcs instead.

[kristin.jakuszanek]

I am just curious why all your dimensions are driven dimensions? This could possibly be why inventor thinks it isn't constrained as well. Have you tried to redimension the 80 constraint so it is driving? Or is there a dimension that is being driven off of in the y axis?

[JDMather]

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@kristin.jakuszanek wrote:

I am just curious why all your dimensions are driven dimensions? 

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They aren't driven dimensions.  They are driving dimensions (Parameters).

Have you tried?

[JDMather]

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@wfp21 wrote:

That's a comforting thought - I am right and Inventor is wrong.

I am approximating the head to an eclipse.

Continue with the design so that we can see where you are going. My guess is that there is no reason to Split the ellipse - you could have used it as originally created.

[kristin.jakuszanek]

Sorry about that, thanks for the correction!

Are you asking if I have tried something or the original poster, though?

[JDMather]

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@kristin.jakuszanek wrote:

...Have you tried to redimension the 80 constraint so it is driving? ....

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[kristin.jakuszanek]

So I am guessing you were redirecting this question back to the OP.

Sorry, still don't quiet understand.

[wfp21]

I have used driving dimensions to set the angle on the eclipse, rather than getting to fully constrained first. I will possibly need to alter these angles and hence why they are not driven.

[kristin.jakuszanek]

The idea of driving dimensions is to have that dimension change based on other parameters updating, for example, if you have a rectangle where you know that the height of the rectangle must always be 5" taller than the length, you would use the driving dimension to reference the driven length so that anytime you update the length of the rectangle, the height will be 5" more than the length dimension. In order for the sketch to be fully constrained you will need at least one driven dimension.

I have included a video to try and explain this better. You will see in the video that I am fully constrained with one driven dimension and one driving dimension, but once both dimensions are driving the sketch becomes unconstrained. 

[SBix26]

Quick note on English language: the geometric form you are creating is an "ellipse", not "eclipse".  They are very different things...

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Sam B

Inventor Pro 2022.2.1 | Windows 10 Home 21H2

[johnsonshiue]

Hi Folks,

This one does look like a bug to me. I cannot explain it. The sketch seems to be fully constrained (no DOF). But, Inventor still reports two dimensions are needed. When I copy the sketch and paste it to another sketch, Inventor reports more dimensions are needed to fully constrain it, which does not make sense.

Many thanks!