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fail to constrain to spline poles

Genius
Genius

It seems to be very odd that I fail to constrain a line end to a spline pole (outside the sketch):

 

  • The blue spline works. (This spline is created in the current example file.)
  • he brown spline fails. (This spline is copied from my model file.)

 

There seems to be no difference between the two splines. Hope to have your suggestions on fixing it. Thanks!

 

Image.png

10 REPLIES

Re: fail to constrain to spline poles

Genius
Genius

The original source of the problematic spline is Isoparametric Curve. I tried with many other isoparametric curve. Even after treatment of Composite Curve, Project Curve, Fit Curve, Remove Parameters, Copy/Paste, ..., the  problem of pole constrain failiure persists. It seems to be a bug with NX 11.0.2. Hope to have a workaround. Thanks!

Re: fail to constrain to spline poles

Phenom
Phenom
@surfactant,

I don't think there is any issue with NX - what you failed to notice was that one spline was planar and the other was not planar. Once you make the problematic spline lie all on a single plane, the coincident constraint issue goes away.
-Tim

Re: fail to constrain to spline poles

Genius
Genius

Hi @TimF   Thank you for your reminding!

 

I just checked it again. You are right. Poles of outside planar splines can be used for constraining in sketch, but poles of outside non-planar splines can't. NX seems to handle the two kinds of splines in different ways. Really a surprise for me. Thanks again!

Re: fail to constrain to spline poles

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

If you really want to constrain to the poles of a non-planar spline, one workaround would be:

  • create an associative point set on the spline's poles
  • project the point set to the same plane that the sketch will use (datum csys plane?)
  • constrain to the projected point

Of course the sketch will need to be a later timestamp than the point set and project features...

Re: fail to constrain to spline poles

Genius
Genius

Hi @TimF,

 

I tried to project the non-planar spline into a sketch. The poles of the resulting planar spline still can't be used for constraining in the sketch.

 

If the non-planar spline is projected onto a plane outside the sketch, there's no problem for constraing in a sketch.

 

It seems to be a little difficult to understand. Thanks!

 

Image.png

Re: fail to constrain to spline poles

Genius
Genius

Hi @cowski1, Thanks for your solution!

 

It seems that your step 2 is unnecessary. Points in the point set are directly usable in sketcher.

 

The point set is definitely associative with the spline. But there seems to be a small issue: the spline is not listed under the Parents folder of the Point Set feature.

 

I had attempted to create points one by one manually on the poles, but failed. Poles simply can't be snapped outside the sketch environment. It's great to know Point Set can do the job.

 

Image.png

Re: fail to constrain to spline poles

Phenom
Phenom

@surfactant

 

A couple of things:

 

  1. Is the Sketch feature to which you projected the spline created before the Sketch containing the 2 lines?  You might need to reorder your features.
  2. You don't have to project to a Sketch - just draw a line between the spline endpoints, but a Datum CSYS at the midpoint of the line with the X-axis in line with the line.  Project the spline onto the XY-plane.  Again, all of these features will have to be before the Sketch with the 2 lines.

 

Of course, that's given all the info presented in the example file you provided - should the splines move dramatically, then this method might need to be reconsidered.

-Tim

Re: fail to constrain to spline poles

Genius
Genius

Hi @TimF   Thanks!

 

You don't have to project to a Sketch - just draw a line between the spline endpoints, but a Datum CSYS at the midpoint of the line with the X-axis in line with the line.  Project the spline onto the XY-plane.  Again, all of these features will have to be before the Sketch with the 2 lines.


Yes. Projecting the spline to XY-plane is ok. And projecting it to a sketch does not work. It seems to be a little odd.

Re: fail to constrain to spline poles

Phenom
Phenom
@surfactant,

While I can't dispute that it seems odd that the projection into another Sketch doesn't work, there's nothing really gained by creating another Sketch and seems to be a bit of overkill when you simply need a planar spline. Keep it simple.
-Tim