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# Constraining an elliptic arc

Valued Contributor

I have an elliptic arc that is part of a closed profile (see below).  The origin, major axis, and minor axis of the ellipse are constrained to the intersection and end points of the line segments.  I would think that would be enough to fully constrain the ellipse, but the sketch is telling me I need one more constraint.  If I click on the ellipse, it gives me the option to set a horizontal or vertical constraint.  What exactly is being constrained to be horizontal or vertical in this case?  Since it's a curve, it's not obvious.  Thanks!

5 REPLIES 5

# Re: Constraining an elliptic arc

Siemens Phenom

An ellipse also has an 'Axis' which is what the suggested constraint is intended to define.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA

# Re: Constraining an elliptic arc

Valued Contributor

@JohnRBaker wrote:

An ellipse also has an 'Axis' which is what the suggested constraint is intended to define.

I thought that was defined by the rotation angle?  Is that not the case?

EDIT

I think I figured it out.  Apparently the rotation angle can still shift in response to other dimension changes (even though the rotation angle is set in the Ellipse dialog).  Applying the horizontal or vertical constraint prevents that.  You can also apply a parallel constraint between the ellipse and one of the lines, which would keep it aligned with the line, even if the line is angled.

# Re: Constraining an elliptic arc

Gears Phenom
That's a curve parameter, NOT a geometric sketch constraint. Just like inputting the length of a line during its creation will not necessarily geometrically constrain it to that length.

Make sense?
Tim
NX 11.0.2.7 MP11 Rev. A
GM TcE v11.2.3.1
GM GPDL v11-A.3.5.1

# Re: Constraining an elliptic arc

Valued Contributor
Yes. I played around with it and realized that (hence my edit above). Thanks for the reply!

# Re: Constraining an elliptic arc

Siemens Phenom

Your sketch is not fully defined. If you draw a line from the origin and let it end on the ellipse (point on curve), then you can still drag it to this shape (see below)

Now it is clear that you need another constraint, like this:

Regards, **bleep**