NX8 DatumAxis normal to a curve

[cucuu]

Hello,

I created a point-set on a curve, and put datumaxes on these points normal to the curve (all of these are associative). When i change the curve shape, the datum axes are reversing due if their basepoints are on a concave or convex curvature. Is there a way to prevent this?

I put the screenshot of what i am talking about. Datums reversed based on the curve shape when i changed the curve. Lets say I want them direct upwards always whatever the curve shape.

Screenshot

 

[JohnRBaker]

I doubt it. The system uses the convexity of the curve to determine the default direction. When that convexity changes, so does the default direction. Reversing the original axis direction only changes how the rule is applied, not that it's no longer in effect.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
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[cucuu]

Thanks for the reply jhon.
Then i guess the only way to do this is to put some associative rules by measurement etc. Maybe reversing the direction depending on angle measurements or such.

 

[cucuu]

Is this rule also applied to the tangent vector? Is tangent datums follow any convexivity rule?

 

[JohnRBaker]

I suspect that the directional sense of a tangent Datum Plane will exhibit the same nehavior.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[BubbaK]

The tangent vector will always be in the direction of increasing parameter value on the curve. It is not affected by the convexity/concavity of the curve, and it should not "flip" in strange ways. So, if you want a normal vector N that always goes to the same side of the curve, compute the cross product cross(T,R), where T is the tangent vector and R is some reference vector.

 

[cucuu]

Thank you Bubbak, i did exactly the same thing. Tangent vectors works like a charm for this matter.